70 XORTH AMERICAN DIPTERA 



fliers tliev can remain in the air for long periods of time and they often 

 occur in large numbers. Williston states that in the Eocky Mountains he 

 has observed them dancing in the air in incredible numbers and pro- 

 ducing a noise like a distant vvaterfall. As a rule they swarm in the 

 evening, but swarms are not uncommon in sheltered places during the 

 day. For the most part only the males swarm, although an occasional 

 female may be found with them. While, as a rule, only one species 

 will be found in a swarm it is not unusual to find other species among 

 them. The females are found mostly on foliage, where they rest on the 

 under surface during the day. Some forms occur commonly on tree 

 trunks, logs, and in grass. They are attracted to light, frequently in 

 very large numbers. 



Since many of the Chironomids are very small they must be han- 

 dled with care. The larger ones may be pinned in the usual manner, 

 provided fine pins are used; the smaller should be attached to the side of 

 a pin by a ring of shellac, care being taken to leave one wdng and the 

 tarsi free. Specimens without front tarsi are almost useless and, since 

 the insects dry quickly, they must be mounted within an hour or two. 



The larvffi are elongate, cylindrical, slender and curved more or 

 less downward, particularly when preserved. The head and legs are 

 conspicuous and there may be one or more pairs of leg-like pads pos- 

 teriorly. They arc scavengers and live in water everywhere, also in mud 

 and have been dredged from a depth of nearly a thousand feet in Lake 

 Superior. Some are also found in decaying vegetation, in moss, etc. 

 ]\Iany of them are free-living while others make mud cases on stones, 

 leaves and pieces of wood and I have found one undetermined species 

 building almost colorless cases in Sinrofj]/r<i. ]\Iany of the larva? con- 

 tain haemoglobin and are red in color, the name ''blood-worms" being 

 applied to these. 



The classification of the family is not entirely satisfactory and 

 characters for the limitation of genera are few. Edwards* has utilized 

 the tibial spurs and combs for the separation of genera, in addition to 

 other characters. However, the classification must be considered as very 

 artificial, although losing nothing on that account. Since the object of 

 taxonomy is the identification of species the means of obtaining the end 

 is not important. IMany papers dealing with the American species 

 have been published since the appearance of Johamisen's monographic 

 revisionf in 1905, by Kieffer, Malloch,^ Johannsen, etc. Some of the 

 more important are listed below. 



* 1929. British non-bitinpr midges. Tr. Ent. Soc. London, Dec. 1929. 

 t 1905. New York State Museum Bulletin No. S6. 

 S 1915. Bull. 111. State Lab. Nat. Hist., x. Art. 6. 



