334 U. S. NATIONAL MUSEUM BULLETIN 2 1 6 part 3 



that coLild be defined as natural populations arc treated below. There 

 are 112 specimens (0.56% of the total) that were left unclassified. 

 These represent several additional species and subspecies, some indi- 

 vidual variants of species or subspecies that we do treat, and some 

 specimens too much broken to be useful. Further progress in the 

 genus is dependent on larger collections and on field studies, but even 

 with the help of these, progress will be slow and imcertain unless 

 additional taxonomic characters can be discovered. 



Correlated with the difficulty of defining the species, keys that would 

 work perfectly for all specimens of all species could not be devised. 

 The keys will bring out correctly all of some species and "typical" 

 specimens of others. For the rest, a consideration of the additional 

 characters mentioned in the descriptions, and some comparison 

 materia], will be needed. 



The cocoons of Trychosis are similar to those of Hidryta and Idio- 

 lispa, but average a little more elongate. They are short elliptic, 

 sm'prisingly small for the size of the adult, dark brown or greyish 

 brown, rather thin but dense, and with a thin layer of paler feltlike 

 silk on the outside. Cocoons of the species montivaga, similis, 

 kathrynae, semirubra, latidens, and cyperia are at hand, the cocoons of 

 all six very similar. Most of the cocoons are pinned with the adults 

 which emerged from them without indications of hosts, but in the 

 cases of semirubra and kathrynae there are some cocoons enclosed 

 within the lenticular egg cocoons of drassid spiders, in both species 

 with pin label notes that the spider egg cocoons were found under 

 rocks. There are a few records from other lands of hosts, but in 

 these cases there is no evidence to show that the host recorded was 

 the true host. Judging by the general ecology and morphology of the 

 species, it seems reasonable to suppose that all species of Trychosis, 

 as well as of the related genera Hidryta and Idiolispa, are parasitic in 

 the egg cocoons of spiders. 



Most of the species occur in grassy and weedy meadows and in 

 openings in woods. A large portion of them are adult only in the first 

 half of the growing season. Almost none are to be found in the fall. 



Keys to the Nearctic species of Trychosis 



MALES 



(The male of sancleri is unknown. It is keyed on the characters it is presumed 



to have.) 

 1. Short carina on prepectus that is opposite or just below lower corner of pro- 

 notum much higher near middle than at ends, in profile subcrescentic; 



tergite 4 entirely or partly black 2 



Short carina on prepectus that is opposite or just below lower corner of 

 pronotum not high at middle, in profile linear or sublinear, or sometimes 



