LIFE-HISTORY OF MIDGES 257 



pupa appears and floats vertically at the surface of 

 the water. It emits the fly directly to the surround- 

 ing air. 



Owl-Midges. Allied to the gnat-family is that to 

 which the midges belong. Of these numerous and 

 varied forms, the minute Ceratopogon, or owl-midges, 

 are amongst the most familiar insects. They form the 

 clouds of minute hairy-winged insects that emerge at 

 sunset from cover, and sting with the virulence of a 

 mosquito. Allied to these owl-midges are other species 

 with smooth wings. The larvae of these insects have 

 a simple worm-like shape. Those of the hairy-winged 

 midges live on the sap of wounded trees, and under 

 the damp bark of dead timber, creeping, and even 

 swimming about with great activity. The larvae 

 of the smooth-winged midges are commonly met 

 with among the confervae at the surface of ponds, 

 and are also active swimmers. In this stage the 

 midges pass the autumn, winter, and early spring. 

 About May the pupal stage is assumed, which is 

 characterised in the midges, as in certain other insects, 

 by its retention of the shrivelled larval skin attached 

 to its tail. Towards the end of this month, or a little 

 later, the winged form appears, only too abundantly in 

 enclosed gardens and the neighbourhood of water. 



The Black-fly (Simulimn). The varied adaptations 

 of dipterous larvae to life in running and stagnant 

 water are of considerable interest, and from the acce- 

 sible, though still imperfectly known life-histories, we 

 may quote two that illustrate these modifications. 



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