B. MOTHS AND BUTTERFLIES (LEPIDOPTERA) 



12. (PRACTICAL.) DISSECTION OF A CATERPILLAR 



Take any large caterpillar, and kill it by placing it in a box 

 with a few drops of ether. Observe the following external 

 characters : — 



The head is small, hard and polished. As seen from the 

 front, it consists of two lateral (epicranial) plates, and a median 

 plate (clypeus) between them. Six simple eyes can be dis- 

 covered on the epicranial plates by 

 examination with a lens ; some are 

 in front, the rest on the sides or 

 behind. The epicranial plates also 

 bear the small, three-jointed feelers. 

 When the back of the head is exa- 

 mined, the mouth-parts come into 

 view. In front is a pair of short 

 and stout mandibles, whose edges 

 are divided into a number of teeth. 

 Behind and in the middle line is a 

 conical prominence, the spinneret, 

 from which in silk-spinning cater- 

 pillars a thread is often seen to 

 issue ; it represents the labium, or 

 fused second maxillae. Outside the from 'Lyon' 

 spinneret appear the maxillae. 



The next three segments constitute the thorax. Each bears 

 a five-jointed leg, ending in a point. The first thoracic seg- 

 ment possesses a spiracle, but the two succeeding segments, 

 which ultimately carry wings, have no spiracles. 



The abdomen consists of ten segments, of which one (the 

 ninth) is not easy to see in most caterpillars.* The number 



* Occasionally, as in Notodonta, the ninth segment is easily seen without 

 dissection. 



SI 



Fig. 42. — Head of larva of goat- 

 moth, seen from behind. Copied 



