198 



CULICID^E, OR GNAT-TRIBE. TIPDLID^E. 



they do head downwards, the respiratory orifice being at the end 

 of a very prolonged spiracle arising from the end of the abdomen. 

 When the final transformation occurs, the skin of the pupa, 

 which is being cast off, serves as a kind of raft, which prevents 

 the perfect insect from being immersed in water, and thus wetting 

 Hs wings. The Mosquitoes, which infest many countries, espe- 

 cially in warm latitudes, or during the brief but hot summers of 

 some colder ones, differ but little from the common Gnats. They 

 sometimes appear in such swarms, especially in marshy districts, 

 that they can be only kept off by fire. Their rapid multiplica- 

 tion is easily understood, when it is known that their whole 

 series of metamorphoses only occupies three or four weeks in 

 summer, so that there may be several generations produced in 

 the course of one season ; and that each female lays several 

 hundred eggs. The TIPULIDJE also have feathered antennae, but 

 their proboscis is very short. Some of them very strongly 



resemble Gnats, both in the 

 larva and perfect states ; 

 such are the Midges, of 

 which one species is repre- 

 sented in Fig. 524. In 

 another group, there is a 

 strong resemblance to the 

 Cynipidee, or Gall-flies ; 

 both in their minute size, 

 veinless wings, and mode 

 of life. Their larvEe are 

 terrestrial, and are very 

 commonly developed within a sort of gall, produced by the punc- 

 ture made by the parent in the tissues of plants, when depositing 

 its eggs. Some species make their puncture in the young sprigs, 

 others in the leaves, and others in the flowers ; and there are 

 several which are extremely injurious both to the Gardener and 

 the Agriculturist. Thus the Wheat crops of this country are often 

 seriously injured by the Cecidomyia Tritici ; the eggs of which 

 are deposited by the female in the centre of the flower, where the 

 larvae are hatched ; and it is probably by devouring the pollen, 

 that they are most injurious to the plant. Another species, 



FIG. 524. CHIRONOMUS, with its Pupa and 

 Larva, magnified. 



