This sub-family of midges consists of very small species varying from 1 to 2 mm. in length; the wings have darkened areas, and the second longitudinal vein is wanting, and the first and third veins are stouter than the others and placed close to the anterior margin, the fourth and fifth are forked; the antennæ in both male and female are composed of fourteen segments, six or eight in the males bearing long hairs.
The chief blood-sucking species belong to the genera Culicoides, Latreille, and Johannseniella, Williston. The latter genus differs from the former in the absence of an empodium or median appendage on the last segment of the tarsi. The genus Ceratopogon, as restricted by Kieffer, is not supposed to take vertebrate blood, but Austen has recently noticed that the type specimen of C. castaneus, Walker, and a new species described by him, apparently have their bodies distended with blood. The wings in the Ceratopogoninæ are carried flat when at rest.
Fig. 403.—A Ceratopogon, or midge. Greatly enlarged.
In spite of their small size the females are the most bloodthirsty and annoying of all insects. The Culicoides, which are often called “sand-flies,” bite during the day and rarely at night. Usually they are most troublesome between 3 and 6 p.m. They frequently attack in swarms, especially in the open, and owing to their minute size can get through fine mosquito netting. Some of them produce a distinct “buzz” when on the wing. These insects are found in all parts of the world. No species has been definitely connected with any disease, but Culicoides has been suspected of carrying the germs of Delhi boil. The larvæ of Culicoides are elongate in form and have smooth bodies composed of thirteen segments including the head, which is horny; there is no proleg on the first segment as seen in Chironomus, and on the anal segment are retractile gills. They are very active and live in the sap of various trees which saturates diseased bark.
The pupæ are smooth, but the abdominal segments bear a transverse row of small spines. Austen describes a number of Culicoides and one Johannseniella and three Ceratopogons from Africa,[401] and Lutz[402] a number of this sub-family from Brazil, including a new genus, Centrorhyncus. Another genus, Tersesthes, Townsend (Centrotypus, Grassi; Mycterotypus, Noe), also occurs in Brazil.
Culicoides ornatus, Taylor, is described from Townsville, Australia, found in mangrove swamps. It is a very vicious biter and causes considerable irritation, settling on hands and wrists (Taylor, Rep. Ent. Aust. Inst. Trop. Med. (1912), 1913, p. 24).
Family. Psychodidæ (Owl Midges).
This family of diptera is of considerable importance, not only on account of the blood-sucking habits of some species, but especially on account of one at least having been proved to be the carrying agent of “papataci” fever, a three-day fever very prevalent in Malta and several parts of Southern Europe in the autumn.