DIPTERA. 4.97 
The two-winged insects constitute one of the most extensive 
orders of the Pritora, not only in respect to numbers of distinct 
species, but also to the swarms of individuals of the same species ; 
and which, from their constant attendance upon man, have attracted 
his attention from the earliest ages. It is not, however, from their 
size that this has been the case, since few species exceed an inch 
in length; nor is it on account of their beauty, for the majority of 
them are of dull colours; their forms, too, are rarely elegant, and 
the transformations of many are unknown. ‘They owe their noto- 
riety, if we may so speak, in many cases, to the disgusting habits 
and appearance of their preparatory states, when many of them revel 
in filth of every description; and to the annoyances caused by the 
reiterated attacks of their numberless tribes in the perfect state, 
both directly upon ourselves, and indirectly upon our living and dead 
property of almost every kind. When it is borne in mind, that one 
of the plagues of Egypt was caused by “swarms of flies”*, and that 
the gnat, the musquito, gad-fly, breeze-fly, Zimb, Stomoxys, &c. are 
Dipterous insects, which are unceasing in their attacks upon man as 
well as upon many of our domestic animals, it will be at once per- 
ceived that the order comprises some of the most formidable of our 
insect enemies. 
Other species, as the Céstri, deposit their eggs upon the bodies 
of animals, within which the grubs, when hatched, feed: others for 
the same purpose infect meat and other viands used for food; and 
so great are their powers of multiplication and voracity, that, accord- 
ing to Linnzeus, “ tres muscze consumunt cadaver equi, eque cito ac 
leo” (Syst. Nat. vol. ii. p. 990.). Other species of flies deposit their 
eggs upon young corn and other fruits of the earth, occasionally 
in such numbers as completely to destroy the hopes of the agricul- 
turist. On the other hand, by clearing the surface of the earth of 
vegetable and animal impurities, and noxious insects, many Dip- 
terous insects are to be regarded as unusually serviceable. 
* In the Brit. Cycl. of Nat. Hist. (vol. iii. p. 298.), and Entomol. Text-Book 
(p. 17.), I have endeavoured to prove (contrary to the opinions of various writers), 
that the plague of flies was produced neither by the zimb, flesh-flies, nor dog-flies 
(xvyouvia), but by “swarms” of musquitoes; the cireumstance stated as mira- 
culous, namely, that the land of Goshen, in which the children of Israel dwelt, 
was not subjected to their attacks, being caused by the sandy nature of the pasture 
soil of Goshen not watered by the Nile, which was consequently free from situations 
favourable for the breeding of Culicide. 
VOL. II. Keke 
