The Cricket Lab. Introduction

Transcription

1 The Cricket Lab Introduction Humans have always been fascinated by crickets, mostly because crickets sing. Movie producers add their songs to sound tracks. The Chinese have used them for medicinal purposes, have special cages which enhance the songs, and fight the males the same way people in other cultures fight dogs or roosters. Some people think crickets bring good luck and, of course, Dickens tells us of the Cricket on the Hearth. Cricket images even appear on ancient cave drawings. Cricket mating behavior is especially fascinating. Males rub their wings together and produce a calling song that is species specific. Females are attracted to the song, and the song repels other calling males in a type of territoriality. In many species, males can be observed walking or remaining stationary, very close to a calling male. This so-called satellite behavior sometimes involves the silent male intercepting and mating with females attracted to the caller. To make matters more interesting, in some species of crickets, parasitic flies have evolved the ability to hear males. They find and lay living larvae on calling males. Males that call and attract females don't live as long as males that spend more time in satellite behavior. Laboratory experiments show that the amount of time that a male spends calling is, in part, due to genetic influences and the maintenance of calling and non-calling male behavior in a population is the subject of much research. What is a cricket? A cricket is an insect. Insects have three main body parts, six legs and antennae. A cricket has two pair of legs that it can walk with and the last pair are longer for jumping. Unlike it's cousin the grasshopper, it tends to be dark brown or black. Crickets also tend to be more active at night although may be seen during the day. Some males like to call from burrows which they defend, while other males and females move from one place to another.

2 How do you distinguish between males and females? One way to identify the sex of a cricket is to look for a long structure coming out of the tail. This structure is the ovipositor that is used by the female to push eggs into the ground while laying. Another way is to look at the wings, female wings are smooth with the wing veins running straight down the back. A look at male wings reveals a wrinkled effect. There are ridges on the wings that form a scraper and a file. When the wings are rubbed together at high speeds a species specific song is produced. What kind of life cycle? The cricket has incomplete metamorphosis. This means that when the tiny nymph (baby cricket) hatches from the egg, it already looks like a cricket. It does not have wings yet, but it's body structure is very similar to the adult only smaller. How do you determine whether or not a cricket is an adult cricket? The best way is to look for wings, Only adult crickets have fully grown out wings. Male and female behavior is also different. Only females can be seen pushing their ovipositor into the soil. Only males sing and fight. Males also defend territory around their burrow. A male calls for two reasons. One is to call in females who are flying around searching for males. Another reason males call is to signal other males to stay away from his territory. How can a fly parasitize a cricket? There is danger in the air on those warm summer nights for the male who is singing. There is a fly that can hear him calling. This fly is a female and is full of larvae ready to drop onto the calling male. The fly locates it's host by listening for a calling male. The fly then quietly deposits the larvae on or near the calling male. The tiny larvae immediately dig through the exoskeleton of the cricket. The larvae live and grow inside the body of the male until it is ready to pupate. At this point it then chews a hole to get out and then pupates on the ground. Why study cricket behavior? The cricket is an ideal animal to study for many reasons. They are small and are easily raised. They demonstrate many behaviors that more complex animals also exhibit. Males call females from long distances in the night. They also have a quiet courtship song when they have found an interested female. The males also have an aggressive song they challenge other males with during a fight. Another behavior some males exhibit is quietly sitting close to a singing male and intercepting any female attracted to the calling male. This is called satellite behavior. When a male takes advantage of finding females without the risk of being attacked by the parasitic fly. A calling male attracts many females but has a short life span due to parasites. The non-calling male does not attract many females at one time but then lives longer and continues to mate. This is seen as the maintenance of two equally successful strategies for mating. This also a classic example of a parasite influence an animal's sexual behavior. Some of these behaviors are can be easily seen in the classroom.

3 W h i t e B B l a c k A Cricket Lab Part 1-Model of a lab Name: Title: Are crickets afraid of the dark? Testable question: Will a cricket spend more time on the white or black paper inside of a Petri bowl? Prediction and Reason: Experiment Materials: Variables: Petri bowl, black and white paper, cricket, timers. Independent Variable=Color of the paper (black or white) Dependent Variable=time Controlled Variables: same cricket, lights off in room, BE QUIET, your position around the bowl is kept the same Experimental Control: Run the experiment with no paper in the bowl. Procedure: 1. Use construction paper to make the ½ white and ½ black bowl as shown by your instructor. Label the bottom of the bowl on the underside with a sharpie A on the black side and B on the white side. 2. Retrieve your cricket from the tank and carry it to your table in the vessel provided by your instructor. Please take care that your cricket doesn t jump out. 3. Place your cricket in a Petri bowl with paper on the bottom that is half black and half white as shown. 3. Collect 2 stop watches from your instructor. Make sure they are working properly. In your group decide who will time the cricket while on the light (white) side of the dish and who will time the cricket on the dark (black) side of the dish. 4. Record the cricket for 5 minutes, keeping track of how much time the cricket spends in the dark and in the light. After 5 min GENTLY shake the bowl and start again. 5. Repeat this trial 3 times, recording your data in the table provided.

4 6. Repeat experiment only this time remove paper from the bowl and record time cricket spends on side A or B of the bowl. Record data in the table. 6. Make a bar graph of your data in the space provided. Collection of Data Don t forget to include your units! Trial Total Time Experiment w/variable Black White Experimental Control side A Side B Analysis of Data (Bar Graph) Black Side Side A White Side Side B Conclusion Recommendations

5 Cricket Lab Part 2-Design Your Own Lab Task: With a partner consider what you have learned about crickets. Choose a TQ that is of interest to both of you. On your own paper design a lab investigation to find a conclusion to your question. MAKE SURE YOUR RESPONDING VARIABLE CAN BE QUANTIFIED (use numbers)! Include all of the sections listed below in the lab scoring guide. Your handout on the Inquiry Science Method you got in class will also be of help to you when designing your lab investigation. Testable Question Includes I and D variables Background Information Linked to TQ and Prediction Prediction and Reason Experiment Includes: Materials Procedure w/logical steps Independent Variable Dependent Variable Controlled Variables Experimental Control Identified Safety Considerations Validity Measures Number & Length of trials Collection of Data More than 1 set of Data Data Table Units Included Analysis of Data Graph or Visual of Data with labeled axis and correct scale Conclusion Restate Prediction Reject or Accept Reasons Why/Use Data Recommendations Possible errors New questions developed Neatness/Organization /3 /10 / Total 0 WHAT DO I TURN IN? Your rough draft report is due for peer evaluation. You get 1 pts EC on your lab if it is peer evaluated IN CLASS. Your final TYPED lab report is due at the start of class. Make sure you include headings for all of the sections of your lab report as outlined in class.