880 Charles Paul Alexander 



G. diversa, Dicranomyia simulans, D. hadia, D. stulta) practice a curious 

 up-and-down bobbing while at rest or while feeding, their long, slender legs 

 acting as springs. 



Swarming and mating 



Swarming usually takes place during the early hours of twilight or 

 in the late afternoon. The swarming of the Limnobiinae is a familiar 

 performance. The number of individuals participating varies from 

 two or three to a dozen or twenty in Rhabdomastix flava, Ilia elegans, 

 Limnophila hrevifurca, L. ultima, and Epiphragrrm foscipeniiis, several 

 hundreds in most species of Ormosia and Erioptera, and vast swarms 

 in species of Trichocera and in Eriocera longicornis, in which many 

 thousands of individuals are involved. In practically all cases the start 

 of the swarm is the same. It begins with one or two individuals and is 

 gradually augmented by the arrival of newcomers. Usually the flight is 

 not far above the ground, that of the smaller species (as in the genera 

 Ormosia, Limnophila, Dicranota, and Rhaphidolabis) taking place under 

 the low branches of a tree or the inclined trunk of a fallen log. In Eriocera, 

 however, mating usually takes place in the open, often over the broad 

 expanse of a river or a stream. The vertical height covered by the dance 

 varies from a few inches in some species to many feet in Brachypremna 

 dispellens, the "king of the dancing crane-flies." Mating takes place 

 during the swarming, and the united pair generally leaves the main body 

 of the swarm and flies away to a resting place. 



The tipuline forms and some of the Limnobiinae (several species 

 of Dicranomyia, species of Hexatoma, Tipula macrolabis, T. fragilis, 

 T. fuliginosa, T. taughannock, and others) seem to mate without the 

 preparatory operation of swarming, the males searching diligently and 

 unceasingly for their mates, walking and fluttering about until they 

 encounter the hiding female and then engaging in copulation. As stated 

 by Needham (1908:215) in the case of Dicranomyia simulans, the males 

 of this species seem to be very short-sighted and apparently unable to 

 see their mates even when very close to them; they seem to rely mainly 

 on the tactile nature of their long, filiform feet, which, the instant they 

 come in contact with any part of the female, apprise the male of its 

 proximity. 



