232 



ZOOLOGY 



Mantis, showing aggressive 

 resemblance. 



holds insects on which it preys. The 

 mantis has the color of its immediate 

 surroundings, and is thus enabled to 

 seize its prey before the latter is aware 

 of its presence. This is known as a 

 case of aggressive resemblance, because 

 by means of its likeness to its sur- 

 roundings the animal is enabled to 

 attack its prey more easily. 



The Order Lepidoptera 



The Monarch Butterfly.^ — The body 

 of the butterfly, as that of the grass- 

 hopper, is composed of three regions. 

 This division of the body is charac- 

 teristic of all insects. 



Compare with the grasshopper as to the 

 number and comparative size of the legs. 

 Notice that the first pair is so short that 

 Compare the wings with those of the grass- 

 Wliich insect probably has the best powers 



they are not used for walking, 

 hopper as to size and shape, 

 of flight? 



If the \\ang is touched with the fingers dust comes off. A bit of the 

 wing examined under the compound microscope shows this dust to be com- 

 posed of tiny scales, which cover the membranous wing somewhat as shingles 

 cover a roof. The scales give color to the wing. Each scale is fastened in 

 place by means of a tiny projection which fits into a socket of the wing. 

 Make a drawing to show several scales and their method of attachment. 



In the fall the following questions may be answered from living butter- 

 flies : How are the wings used in flight ? How are they held when at rest ? 

 What is the position of the legs when at rest ? How are they used in walk- 

 ing? Are any structures present which aid in clinging to objects? 



Let the butterfly feed on sugar and water. The long structure which 

 looks somewhat like a tiny watch spring is the proboscis. Compare its posi- 

 tion when in use and not in use. This organ is formed of the two maxillse, 

 each of which forms half of the tube through which the fluid food is taken 

 into the mouth. 



The fluffy structures on each side of the mouth are the labial palps. They 

 have to do with sensation, probably that of detection of odors. As pollen 



* It is not expected that a pupil can make all the observations noted below 

 on the butterfly and moth as well as on their development. Much of this work 

 can be done as extra observational work when the forms are obtainable.' Work 

 in the early spring (when this study is usually taken up) would preclude the pos- 

 sibility of some of the laboratory suggestions outlined. For laboratory directions 

 see Hunter and Valentine, Manual, page 105. 



