THE LAEVA AND COCOON. »3 



a ventral trefoil-shaped sucker on the 9th and 10th abdominal 

 somites. Microjpteryx and some other specialized larva) are without 

 prologs. 



The larvae periodically cast their skins, the number of moults 

 varying from three to ten in diflferent species, and also varying in 

 the same species under different conditions. 



The somites bear series of tubercles *, from which single hairs 

 or tufts of hair arise : occasionally these are very small and incon- 

 spicuous, or they may be obscured by a general coating of hair 

 spread all over the body ; usually they are distinct and of a definite 

 number. On somite 1 rise hairs from either half of the cervical 

 shield, a prespiracular tubercle with three hairs, and a subspiracular 

 tubercle with one or two hairs : on somites 2 and 3 a subdorsal 

 tubercle, i, with two hairs ; ii with ten hairs, often separated ; 

 iii, iv, & V in line on the side, iv and v being conjoined ; vi sub- 

 spiracuLar, with one or two hairs : on the abdomen i, ii, iii are 

 above the spiracle, iv & v near or below it, vi above the leg, vii on 

 base of leg with three hairs and forming the leg-shield, viii on 

 the inside of the leg. On the conjoined 12th and 13th somites the 

 tubercles are somewhat reduced. 



In the first stage the tu])ercles are in a generalized condition — 

 tubercles iii & iv of thorax and vi of abdomen being absent; these 

 tubercles, therefore, are not primary ones, and they are not developed 

 in any stage of the Pajnliones, Saturniadce, or Sphingida'., or in 

 certain specialized leaf-mining Tineidce. In the divergent Ilejnalidcn 

 they are represented by a different set of subprimary tubercles. 

 In some cases the primitive first stage is absent, and the tubercles 

 are alike in all the stages. The position of the several tubercles 

 varies a little in different families, the change being most marked in 

 the position of tubercle iv of abdomen, which is separate from v, 

 but in line with it in the lowest larvte, and moved up behind the 

 spiracle in the Noctuido', etc. In the higher TlneidiP, and Pyralidiv 

 it becomes joined to v, and in the Splihujidie v is moved up in front 

 of the spiracle. 



The tubercles may be hypcrtrophied into horn-like structures 

 and the hairs variously modified, such as the stinging spines of the 

 Limcfcodidce and the club-shaped appendages of Eriocephala. 



The Cocoon. 



The larva when full-fed forms, for its own protection during the 

 helpless pupa stage, a cocoon composed usually of silk mixed with 

 its own hair, portions of the food-plant, faeces, earth, or similar 

 substances ; in some Syntomidce and Arctiadce of hair only without 

 silk ; or, in the case of the carnivorous forms, of the skins of its 

 victims. 



In some of the more specialized families, however, no cocoon is 

 formed, the pupa being suspended by silk from the extremity of the 



* G. Harrison Dyar, Auu. N.Y. Acad. Sci. viii. p. 194 (1894). 



