514 HYMENOPTERA 



attached to the leaf, somewhat after the fashion of a huge scale- 

 Insect. Some larvae mine between the layers of a leaf, others roll 

 up leaves ; a few live in the stems of plants, and one or two inside 

 fruits. Even this does not complete the list of their habits, for 

 a few species oi Nematus live in galls caused by the deposition of 

 the Qgg. A species of Lyda forms for itself a case out of bits of 

 leaves, and carries this habitation about with it after the fashion 

 of the Phryganeidae. The number of legs in these larvae is 

 unusually great, varying from eighteen to twenty-two that is, 

 three pairs of thoracic legs and eight of abdominal or pro-legs. 

 This character offers a ready means of distinguishing, in the majority 

 of cases, these larvae from those of the Lepidoptera in which the 

 number of legs varies, but is only from ten to sixteen ; moreover, 

 the pro-legs in sawflies are destitute of the circles of booklets 

 that exist in Lepidoptera. This mode of identifying the 

 immature stages of the Tenthredinidae is not, however, always 

 satisfactory, as there are some of these larvae that have no pro- 

 legs at all, but only the three thoracic pairs. Another point of 

 distinction exists, inasmuch as the larvae of the sawflies have 

 only one ocellus on each side of the head, whereas in the Lepi- 

 dopterous caterpillars the rule is that there are several of these 

 little eyes on each side. In addition to this, we should mention 

 that the Lepidopterous larva never has any pro-legs on the fifth 

 body-segment, whereas in the sawflies when pro-legs are present 

 there is always a pair on the segment in question. 



These larvae are of various colours, but the patterns and 

 markings they exhibit are not quite like those of the Lepidoptera, 

 though it would be difficult to make any correct general state- 

 ment as to the nature of the differences. The variety of their 

 postures is very remarkable ; and in respect of these also 

 Tenthredinidae differ considerably from Lepidoptera. Some of 

 them hold the posterior part of the body erect, clasping the 

 leaf by their anterior legs ; others keep the posterior part of the 

 body curled up (Fig. 343, A), and some combine these methods 

 by curving the posterior part of the body and holding it away 

 from the food. These attitudes, like the general form, are 

 characteristic for each species. The Nematus larvae that inhabit 

 galls possess all the characteristics of those that feed externally. 

 As a rule the skin of the larva is naked and free from hair, but 

 it is often minutely tuberculate, and in a few species it is armed 



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