Entomology for medical officers / by A. Alcock.

  • Alfred William Alcock
Date:
1920
Catalogue details

Licence: In copyright

Credit: Entomology for medical officers / by A. Alcock. Source: Wellcome Collection.

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    of malarial fevers, the trypanosomes of sleeping-sickness, certain filarial worm-parasites, and the not yet recognised virus of yellow fever. Blood-sucking flies hardly affect man, though sometimes they may seriously afflict animals, by mere abstraction of blood ; but they ,may cause very serious harm by the pain and venomous irritation of their “ bites,” and by subsequent (septic) aggravation of the bites by scratching. External Structure of Diptera. The head is commonly hemispherical, the posterior surface or occiput being nearly flat. At its sides are the compound eyes, which with few exceptions are large, encroaching on the vertex, and in males sometimes meeting across the crown. Between the eyes lie the antennae. The space between the eyes above the antennae is the front; that between the root of the antennae and the upper margin of the mouth is the face ; that behind and below the eye is the cheek. In addition to the compound eyes many flies possess small simple eyes, or ocelli, which are generally three in number and are set in a triangle, apex forwards, on the top of the head near the occipital margin. The antennae (Fig. i) are one of the principal means of classifying flies. In one great group, of which the mosquito is a good example, the antennae, like those of most insects, are long and slender, and are composed of numerous segments all of which, except one or two at the base, are alike. In another great group, of which the common house-fly is a good example, each antenna consists of 3 dissimilar seg¬ ments, the terminal one being much produced ventrally,
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