A handbook of the gnats or mosquitoes giving the anatomy and life history of the culicidæ / By Major Geo. M. Giles.

  • Giles, George Michael James, 1853-1916.
Date:
1900
Catalogue details

Licence: In copyright

Credit: A handbook of the gnats or mosquitoes giving the anatomy and life history of the culicidæ / By Major Geo. M. Giles. 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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    aperture in the base of the occiput to enter the thorax, where it becomes dilated into a sort of muscular gizzard, which opens behind into a simple transparent tube, the oesophagus. Into the oesophagus, a httle behind its com- mencement, open three structures, viz., the aspiratory vesicle and the salivary and poison glands. These and the rest of the digestive apparatus may easily be demonstrated by dissection in the following manner :—Take a specimen, and place it on a shde with a little salt solution, and carefully remove the legs and wings. Next tear open the thorax, so as to loosen the anterior attachment of the tube, and then carefully partially detach the last two abdominal segments by separating the delicate intersegmental membrane. Now place one needle so as to fix the last two segments, and with the other entangled in the thorax pull steadily on the anterior portion, when the alimentary canal and its appendages will be drawn out intact attached to the hinder fragment. If the operation be successful even the oesophagus and salivary glands will be included in the preparation, but, as a rule, the tube is torn just behind the latter, so that they and the suctorial bulb are left attached to the thorax. Assuming however the preparation to prove a complete one, we find it commences with a narrow tube, which presently expands into a thickly walled, gizzard-like dilata- tion, which is supposed by some to be the apparatus where- by is exercised the suctorial power of the insect. Behind this is a short, constricted portion, which opens in its turn into a long, wide, soft-walled tube, the chyhfic ventricle or stomach. • Immediately after its commencement, the oesophagus receives the ducts of three structures. Of these the two smaller are the two salivary glands, which consist of a pair of short caBcal tubules. These are somewhat broader at their free blind extremities than at their point of attach- ment to the oesophagus, and are fined with a glandular epithehum consisting of rounded or cuboidal cells. In addition to the salivary glands proper a third gland, of very similar structure, can be made out. This is the poison