102 ILLINOIS BIOLOGICAL MONOGRAPHS [102 



the larvae and the lack of secondary setae seem strongly to favor this 

 view. 



Falcaria. This contains the single species, F.bilineata. It has a 

 pair of chalazae on the mesothorax, another on the metathorax, and 

 another on the second abdominal segment. The Pi group on the pro- 

 thorax is borne on a conspicuous protuberance, about as long as the 

 thoracic legs. The setae beta of segment 9 are closer together than 

 setae alpha. 



Drepana. Chalazae as in Falcaria. Prothoracic protuberance not 

 as long as the thoracic legs. The setae beta on segment 9 are farther 

 apart than setae alpha. D. arcuata from the eastern states is dark red 

 above and bears a pair of dorsal chalazae on the first abdominal seg- 

 ment. D. siculifer from the Pacific coast is paler and segment 1 is 

 without chalazae. 



Orcta. Metathorax bearing a single corniculum on dorsomeson 

 Head prominently bicornute. Oreta rosea was the only species examined. 



Family Bombycidae. 



Bombyx mori, the only species of the Bombycidae in North America, 

 shows considerable resemblance to a sphingid but scarcely any similarity 

 to the Saturnioidea, with which it is often placed. The setae are so 

 reduced as to be of little value in identification. The caudal horn is 

 present. Other characters are given in the table for the separation of 

 families. 



Family Lasiocampidae. 



The larvae of the lasiocampids are usually made conspicuous by 

 their large size, long setae and bright colors. They are common leaf- 

 eating caterpillars and some do considerable damage. The number of 

 setae over the entire head and body makes technical description and 

 location in tables difficult. 



Head smaller than body, often retractile, usually depressed; secon- 

 dary setae numerous on all parts ; labrum notched in most species to 

 about one half its depth, notch sometimes continued as a groove which 

 does not, however, extend to the clypeus. Prothorax usually bearing 

 one or two blunt, fleshy protuberances just above the legs, sometimes 

 reduced to mere swellings ; other segments of body sometimes bearing 

 similar swellings. Protuberances always present when the body setae are 

 short and sparse, otherwise the setae are extremely irregular in length, 

 ranging from very short to as long as the body is wide ; setae never in 

 pencils or verricules or on verrucae or scoli. Sometimes a gibbosity or 

 blunt horn is found on segment 8 on the dorsomeson. Prolegs present 

 on segments 3, 4, 5, 6, and 10 as usual; crochets biordinal, arranged in 

 a mesoseries. 



