i68 INJURIOUS AND USEFUL INSECTS 



The fly has four long wings, which are more or less opaque 

 and hairy, resembling those of certain small moths. They slope 

 roofwise when at rest, and the hind pair are folded like a fan. 

 The antennse are long, slender, and many-jointed, the mouth- 

 parts vestigial, but the maxillary and labial palps conspicuous. 

 It is not hard to suppose that the more primitive moths of 

 former days may have been a good deal like caddis-flies. 

 Indeed, one surviving moth (Micropteryx) has a pupa with 

 mobile appendages, and large mandibles for breaking down 

 the cocoon, while the moth has palps very like those of a 

 caddis-fly. Some Lepidoptera are aquatic in their early 

 stages, and case-building caterpillars are known, both aquatic 

 and terrestrial, so that the interval between the Trichoptera 

 and the Lepidoptera is bridged in many ways. 



The chief task of the fly is to get the eggs laid. Sometimes, 

 it is said, the female fly descends into the water and attaches 

 her eggs there. More commdnly they are laid on water-plants, 

 on trees overhanging streams, or on objects at some distance 

 from water. The eggs of some caddis-flies are of grass-green 

 colour, and embedded in a clear, watery jelly, so that when 

 found in a pond or stream they may readily be taken for some 

 colonial alga. 



34. MAY-FLIES (Ephemeridae) 



These insects, the duns, drakes, and spinners of the angler, 

 are not very happily named May-flies, for they are more 

 plentiful in the warmer summer months than in May. They 

 take their learned name, which means insects of a day, from 

 the proverbial shortness of their winged existence. Some live 

 only a few hours in the air, many not more than two or three 

 days. The preceding aquatic stage is longer than in most 

 insects ; many Ephemerids when they emerge have already 

 lived a year, or even two years, as larvse, while in one species 

 the larval stage is believed to occupy as long as three years. 



The species designated as the common May-fly (Ephemera 

 vulgata), which is to be fished out of almost every ditch or 

 muddy stream, is well suited for elementary study. From the 

 eggs laid in summer issue larvEE, which, though very minute in 

 autumn, steadily gain size during the winter. During the first 



