OF WASHINGTON. 



25 



in Donacia and Criocera. It would seem to me, therefore, that 

 before the student of insect larvae will be able to use the setaB and 

 tubercles for the purposes of classification understand! ngly, it 

 will be necessary to know more of their nature, history and 

 origin. Whether the tubercles and setaB of lepidopterous, hy- 

 menopterous, and coleopterous larvae are homologous in any 

 way or whether they had a common origin, seems to me to be a 

 question of importance. Dr. Packard's views as to the origin of 

 the spines and tubercles, and his classification of them, in the 

 Notodontidas may or may not be correct for that family ; it cer 

 tainly has no bearing upon the similar structures found in the 

 Chrysomelidas. 



FIG i. Diagram showing notation of tubercles of the most generalized 

 Chrysomelid larvse. (Represented as one-half of the larval skin is seen 

 when mounted flat.) 



The tubercles as numbered represent those of a purely hypo 

 thetical generalized type, and are not so to be found in any one 

 species. 



On either annulet of the meso and metathorax below the dorso- 

 meson are two tubercles numbered I, II. Ill, IV ; I and III being 

 cephalic. Below these is a larger lateral tubercle extending 

 across both annulets and outlining the forming wing discs which 

 are immediately beneath, which I term V and VI. Below these 

 are two tubercles, anterior and posterior, VII and VIII. The 

 coxa of the leg articulates slightly with the caudal margin of tub 

 ercle IX and caudad of it is X. XI is cephalad of the coxa. 

 XIII dextral and sinistral are usually grown together on the 

 ventro-mesal line. Caudad of them are tubercles XIV, between 

 the coxae. The abdominal segments, I to VII, differ from the 

 thoracic in that tubercles V and VI are separate, VII and VIII 

 are united, as are IX and X, while tubercles XI to XIV are var 

 iously modified. The tubercles of abdominal segments eight and 

 nine are always considerably grown togethe~r>> l __>n the pro- 



