Mosquitoes and Malarial Fever 



493 



part of the thorax. _ As soon as the insect is impaled, the pin should be passed 

 through an opening in a card or_ between the blades of a forceps until the insect 

 occupies a position at the junction of the middle and upper third. The insect 

 should not be touched with the fingers, as the scales will be brushed off and the 

 limbs broken. Mounted insects must be handled with entomologic forceps, 

 touching the pins only. Every insect thus mounted should have placed upon the 

 pin, at the junction of the middle and lower thirds, a small bit of card or paper, 

 telling where and when and under what circumstances it was taken. 



The dissection of fresh mosquitoes for determining whether or not they are 

 infected with malarial organisms must be made with the aid of needles mounted 

 in handles. The position of the stomach, intestines, and the salivary glands, 

 and the mode of pulling the insect apart to show them can be learned from the 

 diagram. The organs thus withdrawn and separated from the unnecessary 

 tissue can be fixed to a slide with Meyer's glycerin-albumin or other albuminous 

 matter, and then stained like a blood-smear, but should be cleared after staining 

 and washing, and mounted in Canada balsam under a cover-glass. 



Fig. 197. — Imago of Anopheles maculipennis escaping from the pupa case upon 

 the surface of the water (Brumpt). 



A more certain and more elegant manner of showing the parasites in infected 

 mosquitoes is by pulling off the legs and wings, embedding the insect in paraffin 

 and cutting serial longitudinal vertical sections. 



To infect mosquitoes and study the development of the malarial parasites 

 in their bodies, the insects should be bred from the aquatic larva in the laboratory, 

 to make sure that they do not already harbor parasites. The mosquitoes 

 are allowed to enter a small cage made with mosquito netting, and are taken to 

 the bedside of the malarial patient, against whose skin the cage is placed until 

 the insects have bitten and distended themselves with blood, when they are 

 taken back to the laboratory, kept as many days as may be desired, then killed 

 and sectioned. In this way, remembering that the entire mosquito cycle of de- 

 velopment takes about a fortnight, any stage of the cycle may be observed. 



