Conorhinus megistus is a Brazilian species very commonly attacking man, and of special interest since Chagas has shown that it is the carrier of a trypanosomiasis of man. Its habits and life history have been studied in detail by Neiva, (1910).
This species is now pre-eminently a household insect, depositing its eggs in cracks and crevices in houses, though this is a relatively recent adaptation. The nymphs emerge in from twenty to forty days, depending upon the temperature. There are five nymphal stages, and as in the case of true bed-bugs, the duration of these is very greatly influenced by the availability of food and by temperature. Neiva reckons the entire life cycle, from egg to egg, as requiring a minimum of three hundred and twenty-four days.
The nymphs begin to suck blood in three to five days after hatching. They usually feed at night and in the dark, attacking especially the face of sleeping individuals. The bite occasions but little pain. The immature insects live in cracks and crevices in houses and invade the beds which are in contact with walls, but the adults are active flyers and attack people sleeping in hammocks. The males as well as the females are blood suckers.
Like many blood-sucking forms, Conorhinus megistus can endure for long periods without food. Neiva received a female specimen which had been for fifty-seven days alive in a tightly closed box. They rarely feed on two consecutive days, even on small quantities of blood, and were never seen to feed on three consecutive days.
Methods of control consist in screening against the adult bugs, and the elimination of crevices and such hiding places of the nymphs. Where the infestation is considerable, fumigation with sulphur is advisable.
Parasitic Diptera or Flies
Of the Diptera or two-winged flies, many species occasionally attack man. Of these, a few are outstanding pests, many of them may also serve to disseminate disease, a phase of our subject which will be considered later. We shall now consider the most important of the group from the viewpoint of their direct attacks on man.
Psychodidæ or Moth-Flies
The Psychodidæ or Moth-flies, include a few species which attack man, and at least one species, Phlebotomus papatasii, is known to transmit the so-called "three-day fever" of man. Another species is supposed to be the vector of Peruvian verruga.
The family is made up of small, sometimes very small, nematocerous Diptera, which are densely covered with hairs, giving them a moth-like appearance. The wings are relatively large, oval or lanceolate in shape, and when at rest are held in a sloping manner over the abdomen, or are held horizontally in such a way as to give the insect a triangular outline. Not only is the moth-like appearance characteristic, but the venation of the wings ([fig. 163, d]) is very peculiar and, according to Comstock, presents an extremely generalized form. All of the longitudinal veins separate near the base of the wing except veins R2 and R3 and veins M1 and M2. Cross veins are wanting in most cases.