Sanitary entomology; the entomology of disease, hygiene and sanitation by Pierce William Dwight 1881- ed

Author:Pierce, William Dwight, 1881- ed
Language: eng
Format: epub
Tags: Insects as carriers of disease, Insect pests
Publisher: Boston, R. G. Badger
Published: 1921-03-25T05:00:00+00:00

Fio. 48.—Eggs and larvae of Culex. Enlarged. (Howard.) From U. S. Dept. Agr.,

Farmers' Bull. 155, fig. 5.

widely separated on the ventral surface, and showing only on middle third of sides. The eggs are laid singly or in small groups upon the surface of the water.

Anopheles quadrimacidatus egg is shown in fig. 4!9b.

THE LARVAE AND THEIR HABITS

All mosquito larvae are aquatic. By far the most of the larvae occur in small deposits of water, although certain species occur in large bodies

Fig. 49.—Eggs of malaria mosquitoes: a, Anopheles punctipennis; b, A. quadrvmacvXa-tus; c, A. crucians. (After Howard, Dyar and Knab.)

of water. Those species which lay their eggs on the ground in dry regions, hatch as soon as rains occur, and the larvae go through a very rapid development. Such species show a rather marked periodicity in broods. Species which have abundance of water breed continuously during the warmer seasons. One is apt to find mosquito larvx wherever water occurs.

The food of the larvae varies, but usually consists of the minute forms

WHAT WE SHOULD KNOW ABOUT MOSQUITO BIOLOGY 269

of plant and animal life in the water, although certain species are predaceous, and some are scavengers upon the dead animals and insect life in their habitat.

The larvae of mosquitoes are very peculiarly constructed. The mouth is furnished with tufts of filaments which are constantly in vibration. The head is large, the antennse long, the thorax somewhat swollen, and the abdomen slender. The sides of the body are furnished with stiff bristles. From the next to the last segment there protrudes a long tube neai'ly as thick as the body itself, and it is this tube that touches the surface of the water when the larva rises to breathe. When in this position the larva ranges downward in various attitudes characteristic of the species. The object of this tube is to get air. At the extremity is a breathing hole, or spiracle, and into it run two main tracheae which extend through the body of the insect with many branches which carry air to all parts

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