Comprises the midges, gnats, crane-flies, gad-flies, &c.
In general appearance mosquitoes resemble many harmless midges (Chironomidae), but may be distinguished by the following characters.
To the traveller, the most conspicuous among the Mexican insects, perhaps, are the butterflies, beetles, ants and the myriads of mosquitoes, midges, fleas and chinches.
That Diptera of the type of the common house-fly are often in large measure responsible for the spread of such diseases as cholera and enteric fever is undeniable, and as regards blood-sucking forms, in addition to those to which reference has already been made, it is sufficient to mention the vast army of pests constituted by the midges, sand-flies, horseflies, &c., from the attacks of which domestic animals suffer equally with man, in addition to being frequently infested with the larvae of the bot and warble flies (Gastrophilus, Oestrus and Hypoderma).
An ear of another type is found in the swollen second segment of the feeler in many male gnats and midges, the cuticle between this segment and the third forming an annular drum which is connected with numerous nerveendings, while the fine bristles on the more distal segments vibrate in response to the note produced by the humming of the female.