THE BUTTERFLY. 41 



3. The next is the largest segment of the leg, the femur. 



4. The next is a slender segment about as long as the 

 femur. It is the tibia. 



5. The remaining segments comprise the foot (or tarsus). 

 Count these tarsal segments. Note what appendages are 

 present, and on which segments. Examine the lower sur- 

 face of these segments. Discover by what means the 

 butterfly is able to walk on the lower surfaces of leaves. 



Examine the wings, noting: 



1. Their action. 



2. Their form. 



3. Their overlapping. 



4. Their covering of hairs and dust-like scales. 



5. Their structure, each a triangular expanse of thin 

 membrane supported by chitinous veins. Find five prin- 

 cipal veins starting outward from the base of a wing. 

 These are named 1 from front to rear, costal, subcostal, 

 median, submedian, and internal. Their branches, when 

 present, are called veinules or veinlets. The subcostal and 

 median are branched in butterflies. The costal and inter- 

 nal are simple. The internal is often very short and 

 inconspicuous in the fore wings. 



Make a drawing of the butterfly as seen from one side, 

 with wings closed, first arranging antennae and feet in a 

 natural position. Make a drawing of it as seen from 

 above, with wings extended. 



With the microscope examine : 



1. The foot. 



2. A cross section of one of the larger veins of the wing. 

 Rub off a few of the dust-like scales of the wing, and 



examine, first with moderate and then with high power, 



1. A bit of the wing with scales attached. 



2. A bit of the wing with scales rubbed off. 



3. The detached scales. Draw. 



1 See footnote, p. 87. 



