THE LIFE CYCLE OF A CRICKET

Transcription

1 THE LIFE CYCLE OF A CRICKET Introduction Insects mature in several distinct stages of growth. Some insects, like butterflies and moths, go through complete metamorphosis. The four stages of development of complete metamorphosis, shown in Figure 1, are egg, caterpillar, pupa, and adult. In contrast, insects that mature through incomplete metamorphosis begin life as nymphs, small versions of the adult. The basic steps of development for these animals are egg, nymph, and adult, although there can be several nymph stages. A maturing insect moves from one nymph form to the next by molting, or shedding, its exoskeleton. A cricket, shown in Figure 2, is a brown or black insect that shows incomplete metamorphosis. The nymph looks like a small adult, but its wings are not fully developed. As nymphs molt and mature, tiny wing pads appear and eventually become wings. With each molt of its exoskeleton, a nymph grows in length. In this experiment you will observe and document the development of crickets from the egg to the adult stage. egg 1 cricket adult butterfly 4 pupa 3 caterpillar 2 Figure 2 Figure 1 Figure 2 Time Needed 55 minutes on day 1 20 minutes on follow-up days (every third day for 3 to 4 weeks)

2 THE LIFE CYCLE OF A CRICKET 2 What You Need small aquarium (or large, clear plastic or glass container) with lid animal food (1 or 2 teaspoons of dog, cat, or fish food) empty cardboard egg carton sterile, insecticide-free potting soil small petri dish large petri dish 5 or 6 cotton balls heating pad (or small gooseneck lamp with low-wattage bulb) spray bottle of water 3 or 4 small paper cups 5 or 6 crickets graph paper ruler (in millimeters) science notebook Safety Precautions Handle crickets and cricket eggs with care, touching them as little as possible. After working with crickets, wash your hands with soap and water. Please review and follow the safety guidelines. What You Do: Day 1 1. Prepare a cricket habitat in a small aquarium with a lid. To do so: a. Place a cardboard egg carton in the container to provide hiding places for the crickets. b. Place animal food in half of the small petri dish, and put water in the other half. Add enough cotton balls to the water to soak it up

3 THE LIFE CYCLE OF A CRICKET 3 so there is no standing water (the crickets can drown in it). Fill half of the large petri dish with potting soil. Place all three petri dishes in the habitat. c. Turn the heating pad to the lowest setting, and position it under the section of the aquarium where the soil was placed. When the crickets lay their eggs in the soil, the heating pad will keep the soil warm and incubate the eggs. (If a heating pad is not available, situate a small, gooseneck lamp with low-wattage bulb to shine on the soil.) d. Spray the soil with enough water to moisten it, but not enough to saturate the soil. Throughout the experimental period, check on the soil and keep it moist with the sprayer. Drying will kill the eggs. 2. Collect five or six crickets from your teacher and place them in their new habitat. Check on them daily to be sure they always have food, water, and moist soil. 3. Every 3 days, examine the soil for cricket eggs by gently moving the soil with your finger. The eggs will resemble white grains of rice. Once you see at least 12 eggs, remove the adults and return them to their original container. 4. Determine the average length of a cricket egg by measuring at least four eggs, then averaging their lengths. To do so: a. Remove the petri dish of soil from the habitat. Gently push aside the soil to reveal some eggs. b. Use the ruler to measure four or more eggs. Record the lengths of the eggs in millimeters (mm) in your science notebook. Avoid touching the eggs as much as possible. c. Find the average length of these cricket eggs by adding the lengths of all four eggs and dividing the total by 4. Record the date and the average length of the cricket eggs in your science notebook. What You Do: Follow-Up Days 1. Continue to monitor your habitat daily. Once the crickets hatch, use a small paper cup to carefully scoop up four of the tiny individuals. Measure the four crickets, then follow the procedure in day 1, step 4b, to find the average length of the group. Record the date and the average length of the crickets in your science notebook.

4 THE LIFE CYCLE OF A CRICKET 4 2. Every third day for the next 2 weeks, use the technique in step 4b to find the average size of the growing crickets. Record the average lengths, and the dates on which you took your measurements, in your science notebook. Observations 1. Based on your observations, how many changes in body shape do crickets undergo after hatching? 2. Using graph paper, graph the average growth rate of your developing crickets. On your graph, place time (in days) on the x-axis and the length (in millimeters) on the y-axis. Be sure to give your graph a name. 3. Write a short paragraph to explain your graph. 4. Why do you think that it is advantageous to crickets to develop rapidly? Want to Know More? See Our Findings.

5 SAFETY PRECAUTIONS Review Before Starting Any Experiment GENERAL Always obtain your teacher s permission for experiments performed at school, and your parent s permission for experiments performed at home, before attempting any experiment. Read all instructions for an experiment before starting the experiment, and follow the directions exactly as they appear in this volume. If an experiment requires adult supervision, do not perform the experiment unless you have an adult supervising you the entire time you are performing the experiment. Wash your hands before the start of and after each experiment you perform. Keep your work area clean. Never eat or drink while performing an experiment. Never taste a substance used in an experiment unless you are told that it is safe to do so. Be aware of the location of safety equipment you may need in an emergency, such as running water, an eyewash if you are at school, and a fire extinguisher. If you are going outside, make sure you have permission to go from your teacher and parent. Take a buddy with you, and dress appropriately for the weather. Make sure you or someone who accompanies you is familiar with the area, and bring along a firstaid kit in case of emergency. Never look directly into the Sun. CHEMICAL SAFETY Always wear goggles when working with chemicals, such as acids and bases, and near heat sources like flames. If at all possible, avoid wearing contact lenses when working with chemicals. If any substance gets into your eyes, notify an adult (e.g., your teacher or parent) immediately, and flush your eyes with running

6 SAFETY PRECAUTIONS 2 water for at least 15 minutes. Do not mix chemicals unless you are told to do so by a teacher or parent. Never touch, taste, or smell chemicals unless instructed to do so. Keep chemicals in closed containers when they are not in use. Dispose of all chemicals properly. Do not pour any chemicals or solids down the drain unless instructed to do so. Use safety gloves and a plastic apron when handling chemicals. If any chemicals spill on your skin, rinse the affected area with running water for at least 10 minutes, and notify your teacher or parent immediately. Take precautions to avoid spilling chemicals. If a chemical spills on any surface, notify your teacher or parent immediately to assist with clean-up. Exercise caution when using sharp instruments such as knives or scissors. Always cut away from yourself, not toward yourself. If you cut yourself, notify your teacher or parent immediately. GLASSWARE Clean glassware when you are finished with the experiment. Be careful when using glassware. If a piece of glassware breaks, have an adult assist you in clean-up to avoid injuries from broken glass. Never use broken or damaged glassware. FIRE SAFETY Do not heat glassware that is not completely dry. Do not pick up hot glassware without heat-resistant gloves or tongs. When heating glassware, keep it away from yourself and from others. Do not heat anything unless instructed to do so by a teacher or parent. Do not heat substances in a closed container. After an experiment, make sure that all heating sources are off and that all flames have been put out.

7 SAFETY PRECAUTIONS 3 Do not reach across such heating sources as flames. If you have long hair, tie it back, out of the way. Do not wear clothing with loose sleeves, scarves, bows, ties, or anything else that may hang into a fire. Do not wear long earrings. ELECTRICAL SAFETY Do not touch electrical equipment when your hands are wet. Do not plug several electrical devices into one outlet or use an extension cord.