vi LARVA 323 



palmer-worm and is composed of a head and thirteen divisions 

 or segments of the body ; the first three of the latter are called 

 thoracic, the other ten, abdominal segments ; in most caterpillars 

 the terminal two or three abdominal segments are more or less 

 run together, and the ninth may be very small, so that the true 

 number is indistinct. The first three segments bear each, on 

 either side, a short limb, ending in a curved spine ; the next 

 two (or three or more) segments are destitute of legs, but on 

 some of the following divisions another kind of leg of a more 

 fleshy character appears, while the body is terminated by a pair 

 of these thick legs .of somewhat different form. The front legs 

 are usually called the true legs, the others prolegs, but this latter 

 designation is a most unfortunate one, the term " pro " being in 

 entomology used to signify anterior ; it is therefore better to 

 call the three anterior pairs thoracic legs, and the others abdominal 

 feet, distinguishing the hind pair of these latter as claspers. 

 There is, too, an unfortunate discrepancy amongst entomologists in 

 their manner of counting the body-segments, some count the head 

 as the first segment, while others apply this term to the first 

 thoracic segment. The latter is the more correct course, for, as 

 the head is not a single segment it should not be called such in 

 a terminology that affects to be morphologically exact, not simply 

 descriptive. The thoracic legs are transversely jointed (Fig. 165, 

 B), but this is not the case with the abdominal feet, which are 

 usually armed beneath with a circle, or with rows, of little hooks. 

 The thoracic legs are, independent of their form, of a different 

 nature from the abdominal, for these latter disappear subsequently, 

 while the former give rise to the legs of the imago. The number 

 of thoracic legs is always six, except in a few cases where there 

 are none at all ; the abdominal feet are much more variable, and 

 exhibit so many distinctions that we cannot here attempt to 

 deal with them. M. Goossens has given a concise and interest- 

 ing account of this subject, 1 and Speyer ~ a summary of the variety 

 in number and position. 



The anatomy of the larva is simple in comparison with that 

 of the perfect Insect ; its main features will be appreciated from 

 Fig. 165, from which it will be seen that the stomach is 

 enormous, and the silk-vessels are also very extensive. There 

 are three sets of glands opening by canals on the head, viz. the 



1 Ann. Soc. ent. France, 1887, pp. 384-404, PI. 7. - Isis, 1845, p. 835. 



