NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS II 



the ovaries are fully stocked with ripe eggs on emergence of the fe- 

 male, ready to be laid as soon as fertlized. In this case the egg-forming 

 material must have been received from the caterpillar. The lepidop- 

 terous caterpillar, therefore, should be a larva primarily constructed 

 for the function of general feeding. According to Stober (1927) it 

 is provided with enzymes for the digestion of sugar, starches, fats, 

 and proteins. Babers and Woke (1937) report that digestive enzymes 

 of the southern armyworm include amylase, maltase, glycogenase, 

 invertase, rennin, lipase, trypsin, and erepsin. The caterpillar is thus 

 evidently equipped to handle any kind of food. It is the dietetic 

 limitation of the adult, therefore, that has brought about the structure 

 of the caterpillar, and the caterpillar is responsible for the life of the 

 adult. An investigation of the caterpillar now will show just how well 

 it has met its obligations. 



THE CATERPILLAR 



A typical modern caterpillar (fig. 5 A) has a long, soft, cylindrical 

 body of 13 segments, and a sclerotized head. On each side of the 

 head (B) is a group of six small simple eyes. The antennae (Ant) 

 are very short, sometimes minute. The mandibles are strong biting- 

 and-chewing jaws (F). On the under side of the head (C) the closely 

 associated labium and maxillae form a prominent lobe containing the 

 silk-spinning apparatus, which opens by a small tapering spinneret 

 (Spn) at the end of the labium. The thoracic legs (A) are very 

 short, but each has the usual six segments of an insect leg (D). The 

 abdomen bears generally a series of short, paired, unsegmented 

 appendages, known as prolegs (PrL), commonly present on segments 

 III-VI and X. 



It is always of interest to know something of the ancestry of any 

 modern animal we are trying to understand, but we know nothing of 

 the nature of the primitive lepidopterous larva. Larvae of the 

 Micropterygidae (fig. 6A,B) have been described and figured by 

 Chapman (1894) and by Tillyard (1922). They look as much like 

 caterpillars as anything else, and the well-developed mandibles could 

 pass for those of a modern caterpillar. The antennae, however, are 

 long and slender (B,C), and in place of prolegs the larvae have either 

 minute points (A) or more slender processes on the first eight ab- 

 dominal segments (B), each ending in a single curved claw (D). 

 According to Hinton (1955), these organs lack muscles, and it is 

 unlikely that they are prototypes of the lepidopterous prolegs. Some 

 micropterygid larvae feed in the open and spin silken cocoons. 



