18 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE 



Species of Basilarchia are distinct from any of the above both in 

 larval appearance and in behavior. The species ar chip pus Cramer 

 is most commonly received, there being only a few collections of 

 astyanax Fab. The food plants of the former are numerous, with 

 poplar and willow most in favor. Like Charidryas nycteis, it passes 

 the winter in the second or third larval stage, but not gregariously. 

 The collections of the early-stage larvse are exceedingly limited, but 

 there are enough data to indicate considerable parasitism by Apan- 

 teles limenitidis Riley. There is at least a partial second generation, 

 and it is not uncommon to find full-grown larvae up to frost. 

 Although of a solitary nature, B. archippus is constant in its appear- 

 ance and is often found in large numbers. Since the larvse in the 

 last stages seem to be peculiarly free from insect enemies (there 

 are no rearing records other than Compsilura), few species are better 

 hosts; and, from the records, it is apparent that Compsilura has 

 made the most of its opportunity. From a total of 81 collections, 

 this parasite has been obtained from 35. Free from competition as 

 it is in this case, it its not at all surprising to find a high degree of 

 parasitism. Some rearing results suggestive of this are as follows: 

 19 larvae gave 48 Compsilura and 5 B. archippus ; 17 larvse gave 34 

 Compsilura and no B. archippus; 10 larvse gave 17 Compsilura and 

 no B. archippus; 3 larvse gave 9 Compsilura and no B. archippus; 

 12 larvae gave 21 Compsilura and 2 B. archippus; 16 larvae gave 26 

 Compsilura and no B. archippus. 



Obviously there is much superparasitism, and individual rearings 

 have often registered from three to seven parasites per host. 



NOTODONTIDAE 



Insects of still another group, the Notodontidae, are to be classed 

 with the favored hosts. These insects commonly appear in the field 

 in late summer and specimens can be found until cold weather puts 

 a stop to all insect activity. 



Species of the genus Datana (integerrima G. and R., ministra 

 Dru., major G. and R., perspicua G. and R., and angusii G. and R.) 

 are gregarious and have a variety of food plants. One species or 

 another is usually abundant in restricted localities; and, although 

 Compsilura is commonly reared during the fall, it has never been 

 reared from overwintering pupae. 13 For some reason, there is great 

 difficulty in rearing some of the Datanas and successfully overwinter- 

 ing the pupae. This is particularly true of the walnut caterpillar 

 (D. integerrima) , a species common on black walnut. Because of its 

 great abundance it is of especial interest as a host possibility, but 

 owing to the heavy mortality of the larva when reared under artificial 

 conditions, there are few data for judging its status. About all that 

 can be said is that it has given one or more Compsilura for three 

 years in five. It was from this host, too, that several Compsilura 

 were reared in 1921, establishing a new dispersion record for that 

 parasite. 14 



13 Since the above was written, Compsilura has been reared on two occasions from 

 overwintering pupae. 



14 A collection of 200 fourth-stage larvae collected at the gipsy-moth infestation at 

 •Greenport, L. I., August 16, 1921, gave five Compsilura in September, 1921. 



