404 



tempt a characterization of the larval and pupal stages of the family, 

 but in pointing out the meagerness of our knowledge I hope I may 

 help to remedy it by directing the attention of some student to this 

 line of investigation, which will repay him more satisfactorily for the 

 time and energy expended than will the writing of new descriptions 

 of imagines the life history of which is entirely unknown. 



HABITS OF LARVAE 



The larvae have been recorded as predaceous upon other insect 

 larvae. They are found in a variety of situations, but a great ma- 

 jority are aquatic. Dolichopiis, Hydrophorus, and Campsicnetntts are 

 among the aquatic forms, and Medetcriis and Thrypticus are found 

 in plants, the latter in the stems of low plants, and the former in bur- 

 rows of other larvae or under bark of trees. The larva of Aphrosylns 

 occurs among seaweed on the shore. 



HABITS OF IMAGINES 



Many of the species occur upon flowers, and several genera, such 

 as Chrysotiis, Dolichopiis, and Psilopus occur commonly upon leaves 

 of plants. They undoubtedly feed upon nectar, but even Psilopus 

 will destroy small insects, as I have seen it catch a small thrips, and 

 though it did not kill it, its actions were such that I am convinced 

 that the species are predaceous. Mcdctcrus I have seen feeding upon 

 a specimen of Forcipomyia. Aphrosylns I know from observation to 

 be predaceous, and Hydrophorus and Campsicncnius have the same 

 habit. 



NOTES ON DESCRIBED SPECIES 



The only identified species that has been recognizably described 

 from North America is Thrypticus nuthlcnhcrgiae Johannsen and 

 Crosby. From an examination of the figures and description of the 

 larva of this species I find that it agrees with that of T. smaragdinus 

 Gerstaeker, a European species, in being peripneustic, and in having a 

 transverse band of locomotor spinules on 8 of the ventral segments, 

 the spinules of the anterior series of each band stronger than those 

 of the 2 or more posterior series. The general shape of the European 

 larva is more uniform than that in the figure of the American, but I 

 suspect that the latter represents a specimen just prior to pupation. 

 The cephalic capsule of the pupa of both species is armed with a pair 

 of protuberances, those of smaragdinus being strong and stout, while 



