EXPERIMENT STATION BULLETINS. 



135 



face of the water, beinj; stuck together, side by side, in large numbers, 

 sometimes more than three hundred in a mass. (The eggs of the mala- 

 rial mosquitoes of the genus Anopheles are said to be laid separately on 

 the water without being joined in a raft-like body.) These eggs hatch 

 usually in one or two days each, by an opening or lid on the underside, 

 giving forth a small wiggler. The wigglers are so well known that a 

 description seems superduous; slender little creatures, each with a 

 swollen thorax and a head at the lower end, and with a breathing-tube 

 at the upper end. Usually the larva rests at the surface of the water, 

 its breathing-tube projecting above the surface film, leaving the head 

 free to feed upon microscopic plants and animals. After a time, vary- 

 ing from a week to several months, the larva changes to a pupa. The 



Fig. 1.— Malaria mosquito, from Howard, Bulletin 25, n. s., U. S. Department of Agriculture. 



skin of the larva splits and the robust, swollen pupa emerges. In this 

 stage the insect breathes by means of two trumpet-shaped tubes which 

 project from the shoulders. After about two days more the pupal skin 

 splits down the back, and spreading open, serves as a support on which 

 the adult insect stands while drying its wings and legs. After this is 

 accomplished, the adult flies away to mate, to lay the eggs for a suc- 

 ceeding brood, and if fortunate enough, to taste human blood. We 

 have in Michigan a number of different kinds of mosquitoes. The 

 commoner sorts belong to the two genera, Culex and Anopheles. The 

 members of the former genus are by far the more numerous in sum- 

 mer time, and are the ones usually seen in the open, and during the day 

 time. They are not known to carry the germs of any disease, but are 

 classed simply as nuisances. Anopheles, on the other hand, seems to 

 prefer such localities as are sheltered by trees, houses, etc., and while 

 it will bite during the day time, it is more apt to choose the night time 



