Morphology of the mosquito vector

The generally 3±6 mm long adult flies possess long slender legs. The head is globular, possessing two large compound eyes (no ocelli) and long filamentous antennae which contain sensory organs to recognize host and oviposition sites and the John ston's organ in the basic segment by which males recognize wing beats of the females. The prominent mouth part is equal in length to the head/ thorax region and formed by the labium ensheathing the stylets which have developed from the labrum (building the food channel), the two mandibles and laciniae and the unpaired hypopharynx, the latter containing the salivary channel. The length, shape and hairiness of the five-segmented maxillary palps differ according to species and sex, being reduced in males which do not feed blood, but only sugars, e.g. honeydew or nectar. In addition, males and females can usually be separated according to the antennae, which are brush-like in males, the weaker developed mouth parts of males and the external genitalia of males, jointed claspers. In both sexes only the veins of the wings are covered with scales. After emergence, male genitalia rotate by 180_, thereby making a copulation during flight easier. The elongated larvae possess a well-sclerotized head capsule, bearing pairs of heavily sclerotized mandibles and maxillae and mouth brushes, the latter helping to scrape vegetation from surfaces or sweeping food particles towards the mouth. One pair of spiracles is located on the fused segments 8/9, almost flush with the surface in Anophelinae or at the end of a sclerotized siphon in Culicinae. In all species, the last segment has a sclerotized saddle with a ventral brush which is used for swimming. On the cephalothorax of the comma-shaped pupae, a pair of respiratory trumpets is located through which the pupae breathe at the water surface. The pupae also possess paddles at the end of the abdomen. There are several criteria to distinguish Anophelinae and Culicinae (Fig. 1A±D): Anopheline eggs are boat-shaped, laid singly and remain at the water surface by air-filled floats. The larvae are surface filter feeders, siphon less and, when not disturbed, they lay parallel to the water surface. Especially adults of the genus Anopheles have at rest all parts (proboscis, head, thorax, and abdomen) in a straight line, holding an angle of 30_ to 45_ to the surface. The wing veins are covered in a Characteristic pattern by dark and pale scales. Scales are usually totally absent from the abdominal sternites. Both sexes possess long, black palps. In contrast to the Anophelines, the Culicines show the following: The larvae hang down at an angle of about 40_ to the water surface or an angle of about 40_ to the water surface or water plants (Mansonia) on which the siphon is located. In resting adults, the body is nearly parallel to the surface or directed back towards the surface. Sternites and tergites are densely covered with scales and the palps of females are not more than one-third as long as the proboscis. Within Culicines, eggs of the three genera can also be distinguished: The black Aedes eggs are laid singly, those of Culex grouped to egg rafts, those of Mansonia glued to the undersurfaces of plants.