277 



have used, wherever possible, such structural characters as were avail- 

 able in addition to those of color, even at the risk of licing charged by 

 superficial students with considering valueless minutiae as of specific 

 importance. My duty to subsequent students of the group is, as I re- 

 gard it, to avoid obscuring the distinctions between genera or species, 

 and to place before them as clear a statement as I possibly can of the 

 characters on which I depend for my identifications, thus enabling them 

 to begin their work upon the family without the handicap which I had 

 when I began — that of uncertainty as to the structural details of genera 

 and species. 



METHODS OF" COLLECTING 



Larva? of CJiironomidcc may l)e met throughout the entire year in 

 almost any permanent body of water, and often in temporary pools. 

 Slow-flowing rivers and creeks and shallow lakes and ponds are 

 both the most easily accessible and most productive of species. 

 Karly in March many species may be dredged from the beds of streams 

 and ponds, and some of them, such as Protcnthes cnliciforinis and 

 OrtJwcladins nivoriiindiis, may be obtained in large numbers in practi- 

 cally any small stream. It is necessary in dredging for larvae that the 

 mud or silt at the bottom should be disturbed to some depth, as most of 

 the species burrow and must be dislodged before they can be obtained 

 with the net. Provided, however, that the net is strong enough, quan- 

 tities of mud may be lifted from the water and sifted over on some con- 

 venient flat surface. The "blood-worms" are readily seen in the net, but 

 most species are difficult to detect because of their brownish or grayish 

 color, and it requires careful searching to find most of the species of 

 Orthocladins and the smaller chironomine species. The wormlike larvae 

 of Ccratopogonincc are also difficult to discover as they are almost 

 colorless and exceptionally slender. A good plan to adopt is that of 

 leaving the material spread out on some smooth surface for a short 

 time undisturbed, when the small larvae may be readily detected by 

 their movements. 



Pupae of Chironomincc and Tanypincc are usually obtained by 

 dredging. Only in rare cases does one obtain them liy searching on the 

 surface of the water, as they seldom leave the burrow or come to the 

 surface till just immediately before the emergence of the adult. The 

 emergence of the imago, which occupies but one or two seconds, us- 

 ually follows so closely upon the appearance of the pupa at the surface 

 that few specimens are obtained while floating. In the aquatic Cera- 

 topogonincc, however, the simplest method of obtaining the pupa is to 

 search along the shore of a body of water upon which a steady breeze 

 has been blowing for some time, or to examine floating objects upon 



