1 INTRODUCTION TO THE STUDY OF ENTOMOLOGY Takumasa Kondo Corporación Colombiana de Investigación Agropecuaria (CORPOICA), Centro de Investigación Palmira, Valle del Cauca, Colombia. Keywords: apiculture, applied entomology, arthropoda, arthropod-borne diseases, basic entomology, biogeography, bugs, Chagas disease, ecological genetics, entomology, entomophagy, entognathology, entognathologist, forest entomology, Hexapoda, Insecta, insect anatomy, insect physiology, insect color pigments, insect molecular genetics, insect morphology, insect pets, insect science, insect taxonomy, medical and veterinary entomology, meliponiculture, phylogenetics population genetics, sericulture, systematic entomology, urban entomology. Contents 1. Introduction 2. What is an insect? 3. Insects and people 4. What subjects are studied in entomology? 5. Basic entomology 5.1. Insect anatomy and insect physiology 5.2. Systematic entomology 5.3. Insect developmental biology/insect growth and development 5.4. Insect ecology 5.5. Ecological genetics, insect molecular genetics and population genetics 6. Applied entomology 6.1. Agricultural Entomology 6.2. Forest Entomology 6.3. Medical and Veterinary Entomology Arthropod-borne diseases Chagas disease 6.4. Urban Entomology 6.5. Apiculture and meliponiculture 6.6. Sericulture 7. Insect color pigments 8. Entomophagy 9. Insects and other arthropods as pets 10. Conclusions Summary Strictly defined, entomology is the study of insects, but often includes closely related arthropods as well. The work of entomologists, the people who study insects is extremely diverse due to the high abundance, species richness, and ecological and behavioral characteristics of insects. This chapter is intended as an introduction to the study of entomology, giving brief explanations and definitions of some chosen topics such as integrated pest management, Chagas disease caused by triatomine bugs, colony collapse disorder of honey bees, red pigments derived from scale insects, the human consumption of insects, and keeping of insects as pets. Emphasis was particularly given to some important aspects of human association with insects.
2 Since early times, entomology has been a very broad subject. Oliver Wendell Holmes Sr. (29.viii x.1894) in his book The Poet at the Breakfast Table (1872) wrote the following quotes that describe the complexities of entomology: I suppose you are an entomologist? I said with a note of interrogation. Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name! A society may call itself an Entomological Society, but the man who arrogates such a broad title as that to himself, in the present state of science, is a pretender, sir, a dilettante, an impostor! No man can be truly called an entomologist, sir; the subject is too vast for any single human intelligence to grasp. 1. Introduction Entomology is a branch of biology that focuses on the study of insects. The word entomology comes from the French word entomologie coined from the Greek word entomon meaning insect + logia meaning the study of. Entomon comes from the word entomos which means "having a notch or cut (at the waist)," so called by Aristotle in reference to the segmented division of the insect body, from en- meaning in + temnein meaning to cut (Online Etymology Dictionary, 2011). In the strict sense, entomology is the study of insects, but entomologists often study other arthropods such as arachnids (e.g., spiders, scorpions and mites), myriapods (e.g., millipedes and centipedes) and even crustaceans (e.g., crabs and isopods). Nevertheless, insects (those organisms belonging to the class Insecta) are studied by entomologists, arachnids are studied by arachnologists and acarologists (those who specialize on mites and ticks), myriapods are studied by myriapodologists, and crustaceans are studied by carcinologists (also known as malacostracologists or crustaceologists). Recent phylogenetic studies have placed organisms previously included in the class Insecta, such as diplurans (order Diplura), proturans (order Protura) and springtails (order Collembola) into a sister group called the class Entognatha. Hexapods (six legged organisms) of the class Entognatha have long been treated as insects, and thus are generally studied by entomologists too. The word entognathology may be proposed as the study of these non-insect hexapods, and the word entognathologist to describe those who study them. 2. What is an Insect? Insects are small animals with 6 pairs of legs that range from less than 1 mm to about 30 cm long. Within the phylum Arthropoda, the classes Insecta and Entognatha (together forming the superclass Hexapoda) have the most developed tagmosis, that is, their body segments are arranged into welldefined functional body parts known as tagmata (singular tagma). Adult insects and entognathans are characteristic in having three tagmata, the head, thorax and abdomen (Figs 1 & 2, left). Besides bearing the mouthparts, the insect head contains many of the sensory organs that perceive and process external information (e.g., antennae, eyes and ocelli). The thorax bears the locomotory organs (i.e., legs and wings). The abdomen contains most of the organs associated with metabolism and reproduction. The insect body is protected by a hard external shell or integument called the exoskeleton, which is composed of cuticle that is secreted by the epidermis. Cuticle is formed of chitin (an amino-sugar polysaccharide) and protein, and there are several layers that vary in development and composition on different areas of the body to allow flexibility or strength of the body wall. Other arthropods have a more reduced type of body segmentation - for example, arachnids have two tagmata, the cephalothorax (or prosoma) and the abdomen (or opisthosoma) (Fig. 2, right). Insects have different types of metamorphosis, but all entognathans have incomplete metamorphosis (see
3 Section 5.3.). Some morphological differences between the Insecta and the closely related Entognatha are as follows (features of Entognatha in parenthesis): (1) mouthparts exposed or in technical terms ectognathous (mouthparts not exposed, entognathous); (2) adults usually with compound eyes and ocelli (eyes and ocelli usually absent, rudimentary when present); and (3) legs composed of six segments (legs composed of four or five segments). Colloquially, insects are often referred to as bugs, however, in entomology; the word bug is strictly used for insects belonging to the order Hemiptera. Insects in this order, especially those of the suborder Heteroptera are known as true bugs. Although insects of the family Coccinellidae (Fig. 11) are sometimes called ladybirds or ladybugs, these are neither birds nor true bugs, but actually beetles, and thus the names ladybird beetles or lady beetles are preferred by entomologists. For common names of true bugs, e.g., assassin bug, leaf-footed bug or giant water bug, the word bug is written separately from its adjective or descriptor. Figure 1. A colorful eumastacid grasshopper (Insecta: Orthoptera: Eumastacidae). Photo by T. Kondo. Figure 2. Comparison of an insect and an arachnid. Left. The fruit fly, Anastrepha striata (Insecta: Diptera: Tephritidae) showing its three main body parts. Right. The crab spider, Gasteracantha cancriformis (Arachnida: Araneae: Araneidae) showing its two main body parts. Photos by T. Kondo.
4 Many insect common names end with the word fly, e.g., butterfly, dragonfly, mayfly, whitefly, but these are really not flies; butterflies belong to the order Lepidoptera, dragonflies belong to the order Odonata, mayflies belong to the order Ephemeroptera and whiteflies belong to the order Hemiptera. In entomology, flies are insects belonging to the order Diptera, and for this group, common names are usually written with the word fly separately, e.g., fruit fly, vinegar fly, deer fly, house fly, etc. 3. Insects and People The first insects appeared on Earth more than 400 million years ago, in comparison to the modern human species that only came into existence only about 50,000 years ago. Insects have long been associated with humans. A list of some insects and insect products that are associated with human life are summarized in Table 1. Table 1. Insects and insect products associated with various aspects of human life. Topic Arts literature Clothing Cosmetics Educational material Energy Food and agriculture Forensic science and Forestry Human health and medicine Jewelry ornaments Museum and Associated insects or insect products Insects are often a subject in literature works and paintings (e.g., butterflies, flies, beetles). In some countries in SE Asia and Brazil, art works made of butterfly wings are commonly sold. Plant fiber and leather product pests (e.g., carpet beetles, clothing moths, screw worms), silk clothes (e.g., silk moths). Ingredients in cosmetics (e.g., bee wax, cochineal dye, honey). Insects (silk moth, cockroaches, crickets, butterflies, others) are often used for teaching art, biology and other related subjects. Caddisfly cases (e.g., Stenopsyche siamensis; Stenopsychidae) can foul flumes in hydroelectric generators and reduce generator efficiency. Agricultural, storage and food product pests (e.g., aphids, army worms, bruchid beetles, cigarette beetles, corn borers, fruit flies, fruit borers, inch worms, Indian meal moth, June beetles, leaf beetles, leaf hoppers, rice weevils, scale insects, schaffers, thrips, whiteflies, wireworms); livestock pests (e.g., house fly, stable fly, horn fly, bot flies, deer flies, horse flies, blister beetles, moths); insects and insect products as a food source (e.g., honey, mopane worms, beetle grubs). The biologies of insects and other arthropods often aid in solving crimes. Insects (e.g., flesh flies, blue bottle flies, various beetles, moths) are often studied in criminal investigations to determine the time of death, original location of a crime, etc. Bark beetles, gypsy moth, woolly adelgids, and other insect pests. Stinging and urticating insects (e.g., bees, carabids, hornets, blister beetles, moths); blood sucking and/or disease vectors (e.g., bed bugs, black flies, ceratopogonid flies, cockroaches, fleas, deer flies, horse flies, house flies, kissing bugs, lice, mosquitoes, sandflies, tsetse flies); insect products use for pharmaceutical purposes (e.g., beeswax, pela scale insect wax, shellac as material for coating pills); aphrodisiacs (Spanish fly). Jewel beetles (buprestid beetles); butterflies; colorful and beautiful insects for display (e.g., butterflies, June beetles, rhinoceros beetles). Cleaning flesh and cartilage from bone specimens (e.g., dermestid beetles).
5 Science Sports Transport and communication Wood building and construction Many species of insects are commonly studied by scientists, but the vinegar fly, Drosophila melanogaster, is probably the most studied organism in biological research, particularly in genetics and developmental biology. Fishing bait (e.g., caddisflies, stoneflies, chironomid midges). Disruption of visibility and slippery road surface conditions (e.g., mayflies, chironomid midges); accidents due to distraction and stings (bees, wasps, others); shellac extracted from the Indian lac insect Kerria lacca may be used as an electric insulator in electric wires; damage to electric wires (powderpost beetles). Wood boring pests (e.g., bruchid beetles, carpenter ants, carpenter bees, deathwatch beetles, longhorned beetles, termites). 4. What Subjects are studied in Entomology? Entomologists may investigate any number of subjects relevant to insects. Some examples include agriculture, anthropology, behavior, biochemistry, biomechanics, developmental biology, ecology, forensic science, insect art (Fig. 3), genetics, molecular biology, morphology, nutrition, paleontology, physiology, robotics, systematics, and various other fields. For example, meteorology is applied to the study of insects as radar technology is used for studying the migratory patterns of insects such as butterflies and dragonflies. Figure 3. Luna moth. Ceramic plate by unknown American artist. Photo by T. Kondo. Entomology is divided into basic and applied entomology. The former deals with the basic aspects
6 of insects, whereas the latter deals with the economic aspects of insects in human society. Nevertheless both basic and applied fields are like two wheels of a cart and must go hand in hand. 5. Basic Entomology Basic entomology (also known as general, pure, fundamental, or theoretical entomology) deals with studies such as biochemistry, biogeography, cytology, ecology, insect development, ethology, genetics, histology, morphology (insect anatomy), paleoentomology, physiology, reproduction, phylogeny and taxonomy Insect Anatomy and Insect Physiology Insect anatomy is the study of the structures (body parts and organs) of insects. It is often taught in courses in general entomology and insect physiology, and is usually divided into external and internal anatomy. The study of external anatomy is called morphology. Morphology is the branch of biology that deals with the form and structure of organisms. In entomology, morphology is important to understand the functions of the various insect body plans and to allow the classification and identification of insects and their relatives. Internal anatomy deals with the internal organs of the insect body, and is often taught along with insect physiology because of the close association of the various organs with essential chemical and physiological processes. The study of minute anatomical structures includes histology (the study of the organization of tissues) and cytology (the study of cells) Systematic Entomology Systematic entomology or insect systematics is the study of the diversity of insects and their interrelationships. Systematics can be subdivided into two fields, i.e., taxonomy and phylogenetics. Insect taxonomy is the science that deals with recognizing, describing, and naming species and groups of species, and the classification of insects into a ranked and named system (e.g., species, genus, family, order, etc.) that aims to reflect a natural evolutionary history. Phylogenetics is the study of the relatedness of organisms or groups of organisms based on shared ancestry. The study of the distribution of insects based on environmental, geological factors and phylogenetic relationships is termed biogeography. More than half of the known species on Earth are insects, with an estimate of 925,000 species described! Within the currently recognized 29 insect orders, the most species-rich orders are the Coleoptera (the beetles) (e.g., Figs 11 & 25) (38% of species), Lepidoptera (butterflies, moths (e.g., Figs 4, 8 & 26) and skippers) (16%), Hymenoptera (ants, bees (e.g., Figs 18 & 19) and wasps (e.g., Fig. 25)) (13%) and the Diptera (flies (e.g., Figs 2 left & 10), gnats and mosquitoes (e.g., Fig. 14)) (12%). The superorder Paraneoptera, composed of the orders Hemiptera (true bugs (e.g., Fig. 6) and others (e.g., Fig. 21)), Psocoptera (bark lice), Phthiraptera (sucking lice) and Thysanoptera (thrips) make up about 11% of the total known insect species. The rest of the 10% of insects are composed by the less species-rich orders: Siphonaptera (fleas), Mecoptera (scorpion flies), Trichoptera (caddisflies), Strepsiptera (twisted-winged parasites), Neuroptera (lacewings, mantidflies, antlions, others), Rhapidioptera (snakeflies), Megaloptera (alderflies, dobsonflies, fishflies), Blattodea (cockroaches, termites (e.g., Fig. 16)), Mantodea (praying mantids) (e.g., Fig. 5), Zoraptera (zorapterans), Dermaptera (earwigs), Plecoptera (stoneflies), Orthoptera (crickets, grasshoppers (e.g., Fig. 1), katydids, locusts), Mantophasmatodea (heel-walkers or gladiators), Grylloblattodea (ice-crawlers or rock crawlers), Embioptera (webspinners), Phasmatodea (stick insects, walking sticks, leaf insects), Ephemeroptera (mayflies), Odonata (damselflies, dragonflies), Zygentoma (silverfish), Archaeognatha (jumping bristletails).
7 Figure 4. Two male geometrid moths. Photo by T. Kondo. Figure 5. A praying mantis (Mantodea) showing cryptic coloration. Photo by T. Kondo Insect Developmental Biology/Insect Growth and Development The study of developmental biology in insects includes such fields as cell biology, embryology, morphology, physiology and molecular biology. Insect growth usually involves a process called
8 metamorphosis; those with gradual metamorphosis are called hemimetabolous insects and those with complete metamorphosis are called holometabolous insects. Furthermore, there are ametabolous insects such as silverfish (Fig. 6) that show no change of body form as they grow and mature. Figure 6. A silverfish (Insecta: Thysanura). Photo by T. Kondo. In hemimetabolous insects, the immature individuals resemble the adults (e.g., Fig. 7), whereas in holometabolous insects, the immatures start as larvae and then go through a pupal stage before developing into adults that differ greatly in morphology from the immature stages (e.g., Fig. 8). Each growth stage, or instar, is separated by a molt (or ecdysis) at which the old cuticle is sloughed off to allow the new and initially flexible cuticle to expand and accommodate the growth of the insect. Molting and growth occur mostly during larval or nymphal instars, and adult insects (called imagos) never molt again, with the exception of mayflies (Ephemeroptera) that have two adult instars. In holometabolous insects, the pupal instar is a resting stage during which major anatomical changes occur in the apparently quiescent insect to transform it from its larval to adult form. Insect life histories differ among species, and even in individuals of a single species depending on the influence of environmental factors such as temperature and moisture. Some topics considered in the life history of an insect may include allometry, sexual dimorphism, polymorphism, migration, resting stages and voltinism. Figure 7. A true bug, Antiteuchus tripterus (Hemiptera: Pentatomidae), tending her eggs and nymphs. Notice the resemblance of the nymphs to their mother. Eggs with dark color have been parasitized by a tiny parasitic wasp. Photo by T. Kondo.
9 Figure 8. The silverspot butterfly, Dione juno (Lepidoptera: Nymphalidae). Left. Larvae. Center. Pupae. Right. Adult. Photos by T. Kondo Insect Ecology Insect ecology considers the interactions of insects and their environment. Insects play an important role in ecosystems and are among the most important organisms contributing to biodiversity. In rainforests and other ecosystems, insects play an important role in nutrient recycling, breaking down animal waste, carrion, leaf litter, and providing the forest floor with rich nutrients. Insects are also important as a food source for many organisms, such as amphibians, birds, mammals, noninsect arthropods and reptiles. Insects interact with other organisms in multiple ways, by transmitting diseases, through competition, predation, mutualisms, parasitism, etc. Insects also interact with plants in many ways, for example, through phytophagy, pollination, seed dispersal, and in some cases by protecting them from herbivores. Insect interactions occur at different trophic levels. A trophic level is the position of organism in the food web (Fig. 9). Figure 9. Trophic levels. Photos by T. Kondo. Primary producers such as plants, algae and fungi are at the trophic level 1; herbivores (primary consumers) are at trophic level 2; carnivores (secondary consumers) are at trophic level 3, carnivores that eat other carnivores (tertiary consumers) are at level 4; and top carnivores are at level 5 (not shown on Fig. 9). The food web often follows a one-way flow, with plants or primary producers being at the base of the pyramid. Trophic paths become more complex in ecological communities with higher biodiversity and by the presence of omnivores that can interact at more than one trophic level.
10 5.5. Ecological Genetics, Insect Molecular Genetics and Population Genetics The field of ecological genetics is the study of genetics in natural populations, often focusing on traits related to fitness (e.g., mating behavior, polymorphism, speciation, mimicry). Insect molecular genetics is the branch of genetics concerned with the structure and function, at the molecular level, of the genetic material (genes) of insects and other related arthropods. It can be used to understand genetic mutations associated with morphological features, disease, pesticide resistance, etc. Topics studied in molecular genetics may include insect chromosome and gene structure, DNA replication, Mendelian inheritance, molecular biology, concepts of inheritance, cell cycles, mutation, biochemical genetics, epistasis, biochemical pathways, genetic systems, genome evolution, genetic control of embryonic development, sex determination, and even transgenic pests and beneficial insects for pest management programs. Advancement in molecular genetics has made possible the wide use of molecular information to determine patterns of descent, resulting in more accurate classifications of organisms, and giving birth to the field of insect molecular systematics. Population genetics studies the distribution and change of allele frequency as a result of evolutionary processes such as gene flow, genetic drift, mutation and natural selection, and aims to explain adaptation and speciation, among other phenomena. Molecular markers are used to determine the presence of hitherto unknown species and to develop fast identification methods, e.g., DNA barcoding. The common fruit fly or vinegar fly, Drosophila melanogaster, has been studied extensively and is a model organism widely used for biological research in genetics (Fig. 10). Figure 10. The vinegar fly, Drosophila melanogaster (Diptera: Drosophilidae), is the most common species used in genetic studies. Photo by T. Kondo. 6. Applied Entomology Applied entomology (also known as economic or strategic entomology) deals with the study of insects that are beneficial or detrimental to humans, domestic animals, and agricultural crops. Beneficial insects include the honey bee, Apis mellifera, which is reared for honey, beeswax, propolis and pollination; the silkworm, Bombyx mori, and the tussah moth, Antheraea pernyi, which are reared for the extraction of silk; the Indian lac insect, Kerria lacca, from which shellac and a pigment known as lake is extracted; the cochineal insect, Dactylopius coccus, from which cochineal dye (known also as carminic acid) is extracted; and many insect pollinators (e.g., bumble bees, honey bees, sweat bees, various beetles and flies) for their role in pollination of agricultural crops. Insects that are consumed as food (e.g., grasshoppers, mopane worm, beetle grubs, others) are considered beneficial and the eating of insects by humans is termed entomophagy (see Section 8). Insect natural enemies, such as parasitoids (e.g., parasitic wasps and flies) and predators (e.g., praying mantises (Fig. 6), lacewings, ladybird beetles (Fig. 11), others) are beneficial because they play an important role in the control of insect pests. It should be noted that some ladybird beetles are phytophagous, for example, those of the genus Epilachna are commonly known as pests of
11 cucurbits (e.g., melon) and solanaceous plants (e.g., eggplant); and although the Asian multicolored lady beetle, Harmonia axyridis (Fig. 11) is commonly known as a beneficial insect because it is a voracious predator of aphids, sometimes it is considered also a pest as is known to cause damage to apples, grapes and peaches, and besides biting, it can cause allergic reactions to humans. An insect may be beneficial or detrimental depending on the circumstances. Figure 11. The multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae). Photo by T. Kondo. An insect is considered a pest when it is harmful to human life, be it directly or indirectly. Species that cause indirect damage by spreading diseases are termed vectors. Some fields included in applied entomology are agricultural entomology, forest entomology, medical and veterinary entomology and urban entomology. Apiculture or apicultural science and sericulture are also subjects dealt with in applied entomology Agricultural Entomology Agricultural entomology concerns the study of insects associated with various aspects of agriculture. Agricultural entomology deals with the study of both beneficial and detrimental insects. Beneficial insects include insect pollinators, such as bumble bees and honey bees; those that produce various commodities such as honey (e.g., honey bees and stingless bees; see Section 6.5.), lac (e.g., the lac insect Kerria lacca) and silk (e.g., the silk moth; see Section 6.6.); and natural enemies (e.g., parasitoids and predators) of agricultural pests. Insects that are detrimental to agriculture (those that cause economic losses) are commonly known as insect pests. Agricultural entomology includes ways to control insect pests, which either cause direct damage to agricultural crops or farm animals by injecting toxins and/or feeding on them; or indirect damage by serving as vectors for diseases. The bulk of agricultural entomology deals with the control of insect pests. Half a century ago, particularly during the time of the green revolution, the philosophy of insect control was centered on eradication of the insect pest, especially through the use of persistent organic pesticides such as DDT. Chemical control was the main control method for many years; however, in 1962, a book entitled Silent Spring, written by Rachel Carson, raised concerns about the impact of pesticides on the environment, including wildlife and human health. Since then, the philosophy of insect control has switched from eradication to maintaining insect populations below an economic injury level, that is, a point where the cost of controlling the pest equals the cost of its inflicted yield loss. Insect pest control is now conducted through integrated pest management (IPM) principles that aim to be sustainable in the use of resources and environmentally friendly. IPM requires plenty of experience and knowledge and combines all available methods of control such as biological control (e.g., use of natural enemies), cultural control (e.g., weed control, fertilization, irrigation, pruning),
12 and mechanical or physical control (e.g., use of barriers, traps, knocking down insect pests with high water pressure), and chemical control, giving preference to products that are less harmful to humans and the environment. In IPM, control begins by knowing the insects that affect the agricultural crops. The first step in insect control is the correct identification of the insect, making taxonomy an important part of any pest control strategy. It is very important to study also the biology of the insect pest, since control may be more efficient at certain times of the insect life cycle; for example, in scale insects, chemical control is generally more effective when the insects are in their first instar (or first growth stage), just after hatching from the egg, because they are more vulnerable as they are smaller and have not developed a protective scale cover at this time. Once they grow older, scale insects produce a waxy cover that makes them less susceptible to pesticides. In IPM, control measures should be undertaken only when necessary. This can be achieved by closely monitoring the insect populations in the field, through visual observation of crops or by the use of monitoring traps, etc. Once the relationship between damage and pest population densities are established, an economic threshold can be defined, where control measures should be started so that the potential pest population will not exceed the economic injury level. An insect should be considered a pest only when its damage exceeds the economic injury level; before that point it is a just a potential pest. There are many insects in the field, but not all insects require control as most do not cause harm and some are beneficial. Prevention is an important component of IPM programs, because by preventing potential pests there is no need of control at all. Cultural control methods such as crop rotation, the use of pest-resistant varieties, or using pest-free plantings, are some common methods of prevention. At a larger scale, prevention can be done also at points of entry, for example, quarantine inspections at airports and ports prevent the entrance of exotic pests to a country. The study of agricultural entomology involves all the basic principles of agronomy, insect ecology, life history and behavior, insect taxonomy, insect physiology, toxicology and other fields of general and applied entomology Forest Entomology Forest entomology concerns the study of insects and other arthropods associated with forest ecosystems. It deals mostly with insect pest management, seeking to control insects that cause crown dieback or death of trees, degradation and destruction of wood, defoliation (Fig. 12), and other problems related to the health of a forest and wood products. Figure 12. Defoliation of a tree caused by leaf-cutting ants, Atta cephalotes (Hymenoptera: Formicidae). Photo by T. Kondo.
13 Forest entomology may include studies on biodiversity, biology and ecology of insects in natural or cultivated forest ecosystems, and damage assessment to tree structures, forest stands and wood products. Insects (and other arthropods) may affect the health of a tree by interrupting its normal growth and causing stunted growth and ruining tree form. Damage caused by insects may include perforation of tree bark, leaves and roots, which often become an entry route for pathogens (fungi, virus, others); crown dieback which consists of a substantial progressive decline in crown health, often resulting in tree death; degradation of wood quality through tunneling caused by insect feeding; staining of the wood either by feeding or by fungi carried by the tunneling insect; destruction of flowers and seeds; and decrease in photosynthetic activity and other physiological processes due to defoliation or injection of toxins, etc. On the other hand, in general, insect populations in forest ecosystems are in balance. But insects are also essential in maintaining healthy forests. Some services provided by insects in a forest include the aeration of soil through tunneling activity improving gas exchange in the root system; decomposition of organic matter of the forest floor; pollination; biological control; food source for other invertebrates and vertebrates that live in the forest; and production of food products such as honey Medical and Veterinary Entomology Medical entomology or human health entomology is the branch of entomology that deals with arthropods that affect human health; veterinary entomology is that branch of entomology that deals with arthropods affecting the health of nonhuman animals, particularly domesticated species. These two disciplines are often combined into a single field known as medical and veterinary entomology. Medical and veterinary entomology involves the study of insects and other arthropods, especially arachnids, and is a broad science that includes studies on biology, ecology, morphology, taxonomy and many aspects related to disease transmission. Medical and veterinary entomology also includes pest control, parasitology, and the study of vector-borne and zoonotic diseases (see Sections and ). Forensic entomology is a specialist branch of medical and veterinary entomology in which insects are used as evidence in criminal investigations. Insects may be particularly important in establishing the post-mortem interval (time since death) in a homicide investigation. Insects develop at predictable rates. Since many of the insects that feed on human cadavers arrive soon after death, information about the developmental stage of these insects can be used to estimate when death actually occurred. Some types of problems caused to humans and other animals by insects and other arthropods include annoyance, envenomation, allergic reactions, invasion of host tissues, arthropodborne diseases, food contamination, phobia for arthropods and delusory parasitosis. Envenomation occurs by the injection of venom by arthropods through bites and stings. In Japan, the giant Asian hornet, Vespa mandarinia (Fig. 25), a species native to temperate and tropical Eastern Asia, is the world's largest hornet with a body length of approximately 5 cm, a wingspan of about 7.5 cm, and a 1 cm long sting that can inject large amounts of a potent venom which has a high content of acetylcholine. Each year as many as 40 people die because of allergic reactions caused by the sting of this species. Other problems may result when poisonous arthropods are touched or ingested; for example, the larvae of some moths can cause allergic reactions to the skin when touched, as in the case of the stinging rose caterpillar Parasa indetermina (Fig. 13).
14 Figure 13. A stinging rose caterpillar, Parasa indetermina (Lepidoptera: Limacodidae) on arm of a volunteer. Notice mild allergic reaction on top right. Photo by T. Kondo. Delusory parasitosis refers to the psychosis that occurs when a person has a strong delusional belief that they are infested with parasites, when they are actually not infested with any. Each year arthropod-borne diseases and new strains of known pathogens are being discovered making the study of medical and veterinary entomology an essential field in human and animal health Arthropod-borne Diseases Numerous human diseases are transmitted by insects and other arthropods that carry pathogens, such as bacteria, flukes, protozoa, viruses, roundworms and tapeworms, between vertebrate hosts. Insects that carry pathogens between hosts are called vectors. Here are listed just a few of the many known vectors of human pathogens. Mosquitoes of the genus Anopheles are vectors of protozoans of the genus Plasmodium, the causal agents of malaria, which is the most deadly arthropod-borne disease, affecting about 250 million people worldwide, with about 2 million deaths accredited to this disease annually. Viruses that are transmitted through the bite of mosquitoes are commonly known as arboviruses (a shortening of arthropod-borne viruses ). The most commonly known arboviruses are those that cause dengue, yellow fever and several kinds of encephalitis (e.g., Venezuelan equine encephalitis, Western equine encephalitis, others). The yellow fever mosquito, Aedes aegypti (Fig. 14), is the main vector of dengue virus, yellow fever virus, and other diseases. Figure 14. The yellow fever mosquito, Aedes aegypti (Diptera: Culicidae) is the main vector of yellow fever and dengue viruses. Photo by N. Burkett-Cadena.
15 Fleas are capable of transmitting the bacterium, Yersinia pestis, the causal agent of plague. Three forms of plague (bubonic, pneumonic, and septicemic) are known to occur in humans. Plague has killed millions of people, especially in the 14th and 17th centuries and is still a problem in society, with some 5,000 cases annually. House flies are vectors of bacteria that cause enteric diseases. For example, typhoid fever caused by Salmonella typhi, cholera caused by Vibrio cholera and shigellosis caused by Shigella spp. cause dysentery and diarrhea, and Escherichia coli causes urogenital and intestinal infections. Triatomine bugs are capable of transmitting the protozoan Trypanosoma cruzi, the causative agent of Chagas disease (see Section ). Deer ticks may act as vectors of the bacterium, Borrelia burgdorferi, which causes Lyme disease in the northern hemisphere. In some parts of Africa, the tsetse flies, Glossina spp., are vectors of two forms of the protozoan Trypanosoma brucei, the causative agent of sleeping sickness or African trypanosomiasis Chagas Disease Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by a flagellate protozoan parasite, Trypanosoma cruzi. The disease was named after the Brazilian physician Carlos R.J. Chagas who first described T. cruzi and its infection in humans in The protozoans invade the muscle cells of the digestive tract, heart, and sometimes the skeletal muscle of their hosts. The life cycle of T. cruzi is complex, consisting of three main developmental forms. The disease is found from the southern USA to Central America and South America and is generally transmitted to humans by the infested feces of triatomine bugs (Fig. 15), although there are other ways of transmission (e.g., via contact of mucosal surfaces, blood transfusion, congenitally, or through organ transplant). Figure 15. A triatomine bug (Hemiptera: Reduviidae: Triatomiinae), vector of the protozoan parasite Tripanosoma cruzi, the causal agent of Chagas disease. N. Burkett-Cadena. Triatomine bugs feeds on blood using their sucking mouthparts. As the bug feeds, it defecates in order to expel excess liquid from its gut. The feces of a bug infected with T. cruzi will contain the infectious parasites. The saliva of triatomine bugs contains anesthetics, anticoagulants and vasodilators that permit the insect to feed without disturbing its host. Once satiated, the insect leaves its human host and the effect of the anesthetic wears off. The bite begins to itch and the sleeping human will scratch the bug bite. The act of scratching disrupts the protective layers of the skin, allowing the protozoans found in the infected feces to penetrate the skin. Chagas disease is typical of poor rural communities, especially among people who live in houses with thatch roofs in
16 areas where the protozoans and their triatomine bug vectors are endemic. Chagas disease affects about 18 million people in Latin America Urban Entomology Urban entomology is the study of insects, arachnids and other arthropods that affect people and their property in urban environments. Some urban pests may cause direct damage to humans through biting and stinging (e.g., ants, bed bugs, fleas, mites, spiders, wasps) and others may cause indirect damage by eating or tunneling their homes and furniture (e.g., carpenter ants, carpenter bees, termites (Fig. 16), damaging paper products (e.g., booklice, silverfish, termites) and fabrics (e.g., carpet beetles, cloth moths), by consuming their food (e.g., Indian meal moths, mealworms), by carrying diseases (e.g., cockroaches, house flies), inducing allergies (e.g., dust mites), by affecting human pets (e.g., fleas, lice, mites), by damaging garden and house plants, etc. Similar to other fields of applied entomology, urban entomology aims to control pests. Medical and veterinary entomology, insect physiology, taxonomy, toxicology, and the study of pesticides and their application are some important components of urban entomology. Figure 16. The subterranean termite, Reticulitermes flavipes (Blattodea: Rhinotermitidae), a common structural pest in the southeastern USA. Photo by T. Kondo Apiculture and Meliponiculture Apiculture or beekeeping is the cultivation of bees for the extraction of honey, beeswax, bee venom, pollen, propolis, royal jelly or for pollination. The nests of cultivated bees are usually called beehives, and these are kept in places known as apiaries (Fig. 17). The collection of bee honey by humans dates back as far as the Neolithic period. One of the earliest records of honey gathering comes from a rock painting, dated to 6,000 B.C., that depicts a person climbing a cliff to collect honey from a bee nest. The most commonly cultivated species of honey bee worldwide is Apis mellifera (Figure 18), which has numerous subspecies and hybrids. A second species, Apis cerana, with its various subspecies is cultivated in many Asian countries. The latter species is smaller in size and produces less honey, but is known to be resistant to the mite Varroa destructor, which is a major pest of A. mellifera. In recent years, populations of cultivated honey bees have been affected by what is now known as colony collapse disorder or CCD, which is a phenomenon in which worker bees of the European honey bee abruptly disappear from their colonies. Although such disappearances have been known to occur previously, the term colony collapse disorder was coined to refer to a drastic rise in the number of collapses of honey bee colonies in the USA in 2006, and since then CCD has also been reported in European countries and even in Taiwan. Colony collapse disorder has raised
17 attention since many agricultural crops rely on pollination by honey bees. The cause of CCD is still not clearly understood, but a great deal of research has been conducted resulting in many hypotheses that try to explain this phenomenon. Colony collapse disorder has been accredited to a variety of factors such as Varroa mites, insect pathogens (e.g., the microsporidian Nosema apis, the Israel acute paralysis virus, and others), environmental and nutritional stresses, neonicotinoid pesticides, genetically modified (GM) crops, etc. Other studies suggest that CCD is caused by a combination of multiple factors. Figure 17. An apiculturist checking his beehives. Photo by T. Kondo. Figure 18. Honey bees pollinating a flower of yellow pitaya, Selenicereus megalanthus (Cactaceae). Photo by T. Kondo. Besides honey bees, stingless bees (Fig. 19) are cultivated in Africa, Australia, and Latin America for the production of honey. The cultivation of stingless bees is termed meliponiculture. Many species of stingless bees are commonly used in Bolivia, Brazil, Colombia, Guatemala, Mexico, Peru and Venezuela for honey production and their use dates back to the times of the Mayan culture.
18 Figure 19. Stingless bees (Hymenoptera: Apidae: Meliponini) at nest entrance. Photo by T. Kondo. Honey from these stingless bees is often used for medicinal purposes such as fertility enhancers, laxatives, for the treatment of ocular cataracts and pterygium, fatigue, gastritis, ulcers, lung weakness, coughs, wounds and bruises Sericulture Sericulture, also known as silk farming, is the cultivation of silkworms for the production of silk (Fig. 20). Many species of silk moth are used for silk extraction, but the most commonly used species is Bombyx mori, a species domesticated from the wild silkmoth, Bombyx mandarina, which is distributed in northern India, China, Korea, Japan, Russia and Turkey. Figure 20. Traditional extraction of Turkish silk. Photo by T. Kondo. The silk thread from a cocoon of B. mori can be as long as 1,000 m. The main food of B. mori is the leaves of the white mulberry Morus alba, however, polyphagous strains also exist that are able to feed on apple fruit and cabbage. Silk production using B. mori began in China around 2,700 B.C. The trade of silk was so important that a trade route called the Silk Road expanded from China towards other Asian territories, the Middle East, Europe and to Africa. 7. Insect Color Pigments Few people are aware that many color pigments and dyes come from animals such as sea snails and insects. Seven species in four families of scale insects (Hemiptera: Coccoidea) are known as a source of red dyes. The body of the lac insect of commerce Kerria lacca contains a dye called
19 lake which is still used in India (Fig. 21). The principal component of the dye of the lac insect is laccaic acid. Lac dye is used extensively as a natural food additive, and can be found in baked foods, candies, chocolate, compound seasonings, fruit and fruit-flavored beverages, ham, ice cream, jam, sausages, soda pop, vegetable juices, and other food products; it is used also in cosmetics and for dyeing silk and cotton. Figure 21. The body of an individual female of the commercial lac insect, Kerria lacca (Hemiptera: Coccoidea: Kerriidae), showing the red pigment. Photo by T. Kondo. The oak-feeding scale insect, Kermes vermilio (Kermesidae), which lives around the Mediterranean shores, produces a red dye that has been known for more than two thousand years. These insects originally were mistaken for little worms, and were given the Latin name vermiculi from which the name vermilion is derived. Another closely related species, Kermes ilicis, has a similar geographical distribution and also is collected as a source of dye. The principal component of the dye of these two species is kermesic acid. There is also a dye known as Armenian red, which is the name given to the red dye obtained from the scale insect Porphyrophora hameli (Margarodidae) that lives mainly on grass roots in Armenia and surrounding countries and was widely used for dying silk products. In Poland and surrounding areas, there exists a related insect, the Polish cochineal insect, Porphyrophora polonica, which also feeds on roots; the insect was widely used in the production of a red dye and exported to Western Europe. In China, Kazakhstan and Uzbekistan there is a third species in the same genus, Porphyrophora sophorae, which also is used as a source of dye. These three species are commonly known as ground pearls because they have a rounded pearl-like cyst stage that does not resemble a typical insect, and for this reason were originally thought to be of plant origin. The principal component of the dye of these ground pearl species is carminic acid. Of all insect dyes, the most famous is the cochineal dye that is extracted from the cochineal insect of commerce, Dactylopius coccus (Dactylopiidae), a species that has been used by Aztecs, Incas and Mayans for more than a thousand years. After the Europeans arrived in the New World, the red dye produced by this insect proved to be superior to any of the red dyes produced by other scale insects in Asia and Europe, resulting in a drastic decline of other scale insect based dyes. It is said that the cochineal insect was so precious that for a time the species was sold at the same price as gold. However, with the appearance of cheap artificial dyes in Europe in the mid-19th century, the demand for cochineal dye dropped drastically. More recently, many synthetic dyes have been found to be carcinogenic, resulting in resurgence in the use of cochineal dye. Currently, the cochineal insect is grown commercially in the Canary Islands, Chile, Mexico and Peru.
20 Figure 22. A drop of the red haemolymph of a cochineal insect, Dactylopius sp. (Hemiptera: Coccoidea: Dactylopiidae), a source of carminic acid. Photo by T. Kondo. The main ingredient of cochineal dye is carminic acid (Fig. 22). Cochineal dye is known by various names, such as carmine, cochineal extract, C.I , crimson lake, E-120, natural red 4, and natural coloring. As a food colorant, cochineal dye can be found in alcoholic drinks, artificial flowers, bakery products, cheddar cheese and other dairy products, cookies, crimson ink, desserts, gelatin desserts, icings, jams, juice beverages, marinades, meats, paints, pie fillings, preserves, processed poultry products, sausages, sauces, toppings, and variety of sweets. Insoluble carmine pigment is used in the cosmetics industry for blushes, hair-care products, lipsticks, face powders, rouges and skin-care products. Cochineal dye is also used in microbiology for staining tissues, and in the pharmaceutical industry to color pills and ointments. 8. Entomophagy The word entomophagy is derived from the Greek words entomon meaning insect and phagy meaning to eat, and refers to the consumption of insects as food, particularly by humans (Fig. 23). The term insectivory is generally used for the consumption of insects by animals other than humans and by some carnivorous plants. The idea of eating insects is not well accepted in Western cultures despite the fact that every day hundreds of insect parts are found in the flour of our daily bread. In rare cases, the consumption of certain insects can induce an anaphylactic shock reaction in susceptible people, as is true for many other food products. Figure 23. The young author (left) eating a fried grasshopper in Thailand. However, recently entomophagy is gaining popularity as reflected by the high increase of entomophagy-related publications, products and insect-eating activities. Entomophagy is common in many parts of the World. In Mexico, for example, more than 200 species of insects are known to be consumed. In general, ants, grasshoppers, beetle grubs (Fig. 24), bee larvae and caterpillars are