A monograph of the Anopheles mosquitoes of India / by S.P. James and W. Glen Liston.

  • James, Sydney Price, 1890-
Date:
1911
Catalogue details

Licence: In copyright

Credit: A monograph of the Anopheles mosquitoes of India / by S.P. James and W. Glen Liston. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    Afiopheline F-gi^s. (PI. I, Fig. 7). When joined together to form the raft they lie vertically with the narrow end out of the water and the broad end—from which the larva escapes—submerged. The eggs of mos- quitoes of the genus Mansonia (Fig. la) have one end terminating in a fine point (Daniels), and those of the genera Stecjomyia and PsoropJiora (Fig. l,b (& c) are pecuhar in that, besides being more or less oval in shape, they possess a rim of cells somewhat resembhi^g the rim or frill present in anopheline eggs. A typical anophehne egg (PI. I, Figs. 2, 3) is a boat-shaped body about 0*7 to 1*0 mm. in length. The upper surface or deck is flattened, but slightly convex, and is surrounded by a narrow beaded rim or frill. One end of the egg is slightly deeper and fuller than the other, and it is toward this end that the head of the embryo is direct- ed. ■ Along the centre of each side of the egg is attached an ova 1 ribbed air-containing float.(see also Fig. 8). These floats are very charac- teristic structures and are not present in the eggs of any other kind of mosquito as yet described. Their shape and position differ in the eggs of different species of anophelines, as does also the width and extent of the beaded rim or frill already described, and Stephens and Chisto- phers have shown that it is possible to distinguish the eggs of some species by the position and characters of these two structures. These distinctions between the eggs of the various species will be described later. THE LARVA. The larvse of all mosquitoes are made upof: (1) the head, (2) the thorax, and (3) the abdomen. The shape and characteristics of these three regions differ in the various sub-famJlies, genera and even species of mosquitoes, but the characters of the abdomen afford the readiest means of distinguishing between the main groups and m.ust therefore be described first. The abdomen is divided into nine segments. The first seven segments closely resemble one another and need not be specially described. The eighth segment carries the external openings {.stigmata) of the respiratory tubes or trachece, by means of which oxygen is supplied to the tissues of the larva. In all anopheline larvse the two large tracheae open directly on the upper surface of the eighth segment by two stigmata which are surrounded and supported by a complex apparatus (PI. I, Fig. 8). In the larvee of other kinds of moscjuitoes 5