^ THE INSECT WORLD. 



and employ the most varied and ingenious precautions to preserve 



*' The°Diptera, besides their variety and the number of their species 

 are Remarkable ^n account of their profusion. The myriads of flies 

 which^Sffrom our meadows, which fly in crowds around our plant , 

 rn-Taround every organised substance from which life has departed, 

 some of which even infest living animals are Uiptera. 



The profusion with which they are distributed over the face of the 

 dobe ciuses them to fulfil two important duties in the economy of 

 f^atoe" the one hand, they furnish to insectivorous birds an 

 ^exhaustible supply of food; on the other, they contribute to the 

 emov^ of aU decaying animal and vegetable substaiices and thus 

 seTe to purify the air which we breathe. Their fecundity, the rapidity 

 wTtlwhich one generation succeeds another, and their great voracity^ 

 Tdded o Ae exteordinary quickness of their reproduction are such 

 Aat LinnLs tells us that three flies, with the generations which spnng 

 from them could eat up a dead horse as quickly as a lion could. 



T ese Sptera, which are worthy of so much attention, and 

 deserve so much study with regard to the part they pay m the 

 generll economy of Nature, are an object of fear and repukion when 

 one considers their relations to us and other animals. Gnats and 

 mosquitoes suck our blood; the gad-fly and the species of Asilu 

 attack our cattle. The order Diptera is composed of a great number 

 of families, which are again divided into tribes, each comprising 

 several genera. We shall only notice the more remarkable genera ot 



^''^M^^Macquart, the learned author of " L'Histoire Naturelle des 

 Dipteres,"* divides this great class of insects into two pnncipal groups. 

 In one of these groups, the antennae are formed of at least six joints 

 and the palpi of four or five: these are called Nem°cera In the 

 other, the antenna; consists only of three joints, and the palpi of one 

 or two : these are the Brachycera. . , , r n .= ..fl,sr 



The Neraocera may generally be distinguished from the other 

 Diptera, independently of the difference in the antennae and palpi, by 



* " Suites a Buffon." 2 vols. Svo. 



