INSECTS, AND THEIR RELATION TO MAN 171 



Observations. 1. Where are the wings located ? 



2. What is the natural position of the wings when folded ? 



3. What is the relative position of the wings when out- 

 spread ? 



4. W T hat differences do you note between the two sets of 

 wings ? 



5. Observe that the margins of the fore wings are straight. 

 Does an aeroplane resemble them in this respect? Are they 

 tough ? 



Conclusion. What is the probable difference in function of 

 the two sets of wings ? 



3. MOUTH PARTS 



Observations. 1. Are the lips that cover the jaws mov- 

 able? 



2. With a lens note the teeth on the jaws. 



Conclusion. Which way must the jaws move in biting 

 food? 



4. SENSE ORGANS 



Observations. 1. Note the length, shape, segmentation, and 

 place of attachment of the " horns " (antennae). 



2. Find the large eyes. Where are they situated? Ex- 

 amine them with hand lens. Are they compound ? Explain 

 your answer. 



3. Examine a section of a compound eye with low power of 

 a portable microscope, and note the facets. Sketch a few of 

 them. 



4. Find a simple eye (ocellus) on the ridge between the 

 antennae? Find a similar one above each antenna? 



5. Find a pair of ear membranes on the first segment of the 

 abdomen. Lift the wings to find them. 



Conclusions. 1. Can a grasshopper see anything approach 

 from behind ? Explain ? 



2. Has a grasshopper the sense of hearing ? Note. Organs 

 imply functions. 



