77] LEPIDOPTEROUS LARVAE — FRACKER 77 



Bemhecia marginata. Crochets very small, ten to fifteen in a row; 

 spiracles slightly chitinized ; setae strongly developed ; segments triannu- 

 late; adfrontals not reaching vertical triangle. 



Alcathoe caudata. Similar to Bembecia except that the crochets 

 are larger and are heavily chitinized. 



Family Cossidae. 



The Carpenter moths received their popular name from the larval 

 habit of boring in trees. This form of life has modified the structure, 

 especially of the head, and has caused the development of rather heavily 

 chitinized pinacula for relatively reduced setae. Many of the species 

 attain considerable size and their larvae are some of our largest 

 caterpillars. 



Head broad, usually longer, if not higher, than wide, smaller than 

 prothorax to which it is closely united; front varying from one third 

 to one half height of head; dorsal four ocelli forming nearly a semi- 

 circle distant from the fourth and fifth ; labrum truncate at tip, with a 

 scarcely perceptible emargination ; mandibles very large. (Fig. 72.) 

 Body widest at prothorax, narrowest at beginning of abdomen, bearing 

 primary setae only. Prothorax with rho directly caudad of epsilon, 

 Kappa group trisetose. Mesothorax and metathorax as in Tortricidae 

 (Fig. 40). Abdomen with kappa and eta adjacent; epsilon usually pres- 

 ent cephalad of spiracle, sometimes large; beta above level of alpha on 

 segment 9. Prolegs present on segment 3, 4, 5, 6, and 10; crochets 

 various. 



Genera of Cossidae: 



a. Crochets uniordinal, arranged in two transverse bands; prothorax 

 bearing a large, dorsal, semicircular, rugose plate on its caudal half ; 

 spiracles of segment 8 two or three times as large as those of seg- 

 ments 1 to 7 and located much nearer dorsomeson. Cossula 

 aa. Crochets biordinal or triordinal, arranged in a complete circle, 

 b. Prothoracic shield with the caudal margin smooth and not elevated ; 

 spiracle of segment 8 in line with those of segments 1 to 7, below 

 rho. 

 c. Setae alpha of middle abdominal segments only two-thirds as far 

 apart on dorsum as setae beta. Prionoxystus 

 cc. Setae alpha of middle abdominal segments more than three- 

 fourths as far apart as setae beta (in American species). 



Cossus 



bb. Prothoracic shield with the dorsal half of the caudal margin 



conspicuous and strongly rugose; spiracle of segment 8 higher 



than those of segments 1 to 7, caudad of rho. Zeuzera 



