834 Charles Paul Alexander 



seasonal distribution 



Like many other groups of insects, the Holarctic crane-flies have 

 a remarkably constant seasonal distribution, there being vernal, early 

 summer, midsummer, and autumnal species, as well as forms that range 

 over a much longer period. The vernal species appear soon after the 

 melting of the ice in spring, and are on the wing for a month or two. 

 Some few of these species reappear in late summer, and these are pre- 

 sumably double-brooded species. In New York, New England, and 

 southern Canada the great majority of crane-flies are on the wing during 

 the month of June. Among these are represented the last of the vernal 

 forms and the first of the extensive midsummer fauna. In late summer 

 a few additional species appear, and these are closely followed in Sep- 

 tember and October by about the same number of autumnal forms. The 

 winter crane-flies, so-called, include species of Trichocera and Chionea 

 which appear at other seasons of the year as well but are more easily 

 detected during the mild, sunny days of winter. 



In general it may be stated that the crane-flies of eastern America 

 which fly in spring and summer come out later and disappear earlier in 

 the northern part of their range • — New York, New England, and southern 

 Canada — than in the southern part — the Middle Atlantic and Southern 

 States. The late summer and the autumnal species, however, come 

 out earlier in the former regions than they do farther south, and disappear 

 correspondingly early in the season, their period being restricted by the 

 date of the first killing frost. 



The dates as here given apply to the Transition areas of New York 

 and New England. They -should be considered as earlier in the vicinity 

 of Washington — from one to three weeks or even more, depending on 

 the situation — and later as one goes northward, with the exceptions 

 given above. It must be understood and expected that considerable 

 deviation from these dates and figures will be found, but it is believed 

 that in most cases they are fairly accurate, being based on a vast number 

 of records extending over many years. 



The following are early to late spring species — from April 1 thru 

 May, disappearing about the first of June but many of them reappearing 

 in August and September. Most of these species appear for the first 

 time about April 20. Helobia appears nuich earlier, in March or even 

 in February. The species of Ormosia, Dicranota, and Rhaphidolabis are 



