Investigation of the life of the praying mantis

Transcription

1 INTRODUCTION Investigation of the life of the praying mantis Praying mantis (Orthodera novaezealandiae (Colenso)) was first recorded in New Zealand in the 1870s. It is found throughout New Zealand, although it is absent from the West Coast of the South Island (Ramsay 1990). The life cycle of Orthodera novaezealandiae is univoltine: nymphs emerge in spring, mature in summer; adults mate and produce eggs in autumn, and die at the onset of winter. Egg-laying starts in February and continues while the females survive, which may be until April May. The juveniles will spend five to six months in the egg case until hatching in spring-summer. Nymphs move through six instars, with the first adults appearing in mid-february (Ramsay 1990). Praying mantis eggs are laid in batches in egg cases, called ootheca. The ootheca is light brown in colour. The female constructs them by moving her abdomen side to side to lay down a continuous ribbon, enclosing two staggered rows of egg chambers. The strong outer case is formed at the same time by producing foam which sets hard (Walsby 1996). The number of eggs in each ootheca is very variable, being as high as 70 and as low as 5, with most common (34 average) (Suckling 1984). The young mantids require a steady supply of prey such as fruit flies (Drosophila spp.). At each nymphal stage, the nymphs can safely tackle progressively larger prey. Adults can safely secure wasps, honeybees, grasshoppers and blowflies. If the strike is not completely successful the mantis does not attempt to obtain a better grip, but releases the potential problem as quickly as is possible (Walsby 1996). Oothecae are often found on exposed parts of tree trunks or branches and human-made structures such as fences and posts (Walsby 1996) and tend to be on trees with unshaded trunks (Bowie and Bowie 2003). Bowie and Bowie (2003) found that the direction faced by ootheca concentrated around true north, presumably to maximise sunlight and heat and hasten egg development. Many modern New Zealand houses face true north to capture more light and heat. Consequently, northfacing surfaces, such as walls and fences, can have Orthodera novaezealandiae oothecae because their height, aspect and temperature suits egg hatching. REFERENCES Bowie, M. K., and Bowie M. H Where does the New Zealand praying mantis, Orthodera novaezealandia (Colenso) (Mantodea: Mantidae) deposit its oothecae? New Zealand Entomologist 26:3-5. Ramsay, G. W Mantodea (Insecta) with a review of aspects of functional morphology and biology. Fauna of New Zealand 19:1-96. Suckling, D. M Laboratory studies on the praying mantis Orthodera ministralis (Mantodea: Mantidae). New Zealand Entomologist 8: Walsby, J On a wing and a prayer. New Zealand Geographic 29:

2 DESCRIPTION of PRAYING MANTIS Praying mantis have one generation per season (Fig. 1), and the adults do not survive the winter months. The eggs are in the egg cases for approximately six months and take another 3-6 months to develop as adults. Praying mantis eggs are laid in batches in egg cases (ootheca) (approx. 15mm long). The female constructs them by moving her abdomen side to side to lay down a continuous ribbon, enclosing two staggered rows of egg chambers (Walsby 1996). Photograph courtesy of David Hollander. Adult New Zealand praying mantis are always green with bright blue patches on inner forelimbs (Walsby 1996). Photograph courtesy of Kennedy Warne. The juveniles will spend five to six months in the egg case until hatching in spring-summer. Young pronymphs rapidly undergo a moult to become a nymph. (Walsby 1996). Photograph courtesy of Brian Chudleigh. Nymphs then go through six instars, taking three to six months until becoming adults (Walsby 1996). Photograph courtesy of David Hollander. Fig. 1: Lifecycle of the praying mantis.

3 How to rear praying mantis Rearing praying mantis requires a good supply of small insects, such as fruit fly. Figure 2 shows a praying mantis feeding on a fly. It is also important that when the nymphs hatch that they are placed in individual containers with adequate ventilation. This is because they may eat each other. Inside the containers there should be a source of moisture, i.e. a piece of foam rubber. There should also be a string going across the container, especially in the later instars because the nymphs like to hang down to shed their old skin. Figure 3 shows what a container for a praying mantis could look like. Figure 2: A praying mantis eating a fly. Figure 3: A container for a praying mantis.

4 The Investigations: 1. To determine where praying mantis deposit their oothecae. (Field work to be carried out in February-May) Procedure: Search fence posts, trees, buildings in unshaded spots. Results Record results in a table under these headings: Table 1: Location of Orthodera novaezealandia oothecae Date Location site Type of surface Height from ground Orientation Number of eggs per ootheca Size of ootheca Development Notes: Conclusion What conclusion can you draw on where the adults have laid eggs? Suggestions for further investigations 2. Rearing praying mantis in laboratory Procedures Praying mantis can be reared, in individual containers with mesh ventilation, in the laboratory by taking ootheca and placing them under artificial light and heat. Ensure that there is a source of live small insects available for a food source when the nymphs are hatched. Fruit fly (Drosophila melanogaster) is a good food source to start with and progress to larger insects as they grow. Results Record results in a table under these (or other) headings: Ootheca no. Time hatch to Light/heat source Orientation If you have sufficient ootheca you could investigate the effect of temperature or orientation of ootheca on the development of praying mantis Keep in mind: What other factors need to be kept constant? How would you control each of these factors and why? Why must you use more than one praying mantis egg case when you are doing investigations? Discussion

5 Find out about other species of praying mantis found in other parts of the world. Discuss the likely impact of other praying mantis species arriving in New Zealand. Discuss the effect that the praying mantis has on the fauna of New Zealand. For further information contact the author Craig Sixtus on either or extension 8460.