350 THE NEMOCERA. 



hundred British species; its larva lives in the mnd 

 of stagnant water and in drains, and is well known 

 to the angler under the name of the Blood-worm. 

 The pupa also lives at the bottom of the water, 

 and is capable of swimming about; its respiratory 

 organs consist of a small star of hairs on each 

 side of the thorax and a tuft of diverging hairs at the 

 tail. When the perfect insect is about to emerge, 

 the pupa rises to the surface of the water, above which 

 it protrudes the back of its thorax, and then escapes 

 very much in the same way as the gnats. 



Besides these, numerous other species are aquatic in 

 their preparatory states, and their larvae and pupa^ ex- 

 hibit a considerable diversity of structure, to which, 

 however, my space will not allow me to refer. Amongst 

 them a few, belonging to the genus Simulium, which 

 are well known under the name of Sand-flies^ appear 

 to be in many countries even greater pests than the 

 Mosquitoes ; indeed, in some places the latter name is 

 applied to species of this genus. These insects, al- 

 though of very small size, bite most severely, pro- 

 ducing exceedingly painful swellings, which often 

 remain for a considerable time. 



The majority of the species of this tribe are, how- 

 ever, quite incapable of maldng any attacks upon us 

 in their perfect state, their mouths being but slightly 

 developed in comparison with that of the Gnat and 

 its allies, and organized solely for the imbibition of 

 the juices of flowers. In the larva state, however^ 

 many of them are exceedingly injurious to vegetable 

 produce, and the larva of the common Daddy Long- 

 legs (Tijmla oleracea), which lives in the earth and 

 feeds on the roots of grasses, often lays bare large 

 tracts of meadow land by its subterranean ravages. . 





