June, 1906.I KNAB : GOELDl'S " OS MOSQUITOS NO PARA." 61 



pointed out. A count of the eggs in two egg-boats of Culex fatigans 

 gave respectively 270 and 225 eggs. 



There is an interesting observation on the difference in food habits 

 of the two sexes. Outdoors the males feed on ripe fruits and flowers ; 

 in the house they go to sugar, coffee, tea, wine, soups and all sweet 

 substances, and abstain from sucking blood. The females are blood- 

 suckers and the difference in food habits is brought out in the follow- 

 ing experiments. In the first experiment mosquitoes were observed 

 swarming about the sugar bowl. It was quickly covered with a paper 

 cone and the mosquitoes within chloroformed. There were 37 dead 

 mosquitoes — 1 $, 1 Q Stegomyia fasciaia, and 33 $, 2 Q Culex 

 fatigans. This experiment was repeated a number of times with only 

 a slight variation in the percentage of the sexes. This was in the 

 dining room, the second contrasting experience in the bed-room. Far 

 in the night the author noticed that outside of a certain part the mos- 

 quito-bar, close to his face, the mosquitoes were dancing up and 

 down in a manifest endeavor to find a hole that would admit them. 

 With a sudden slap of the hand a number of them were crushed against 

 the wall. Examination showed that there were 23 dead Culex fati- 

 gans — all females. And thus, in the bed rooms, there always proved 

 to be an enormous majority of females in quest of blood, to the ex- 

 clusion of the males. 



An explanation of the blood-sucking habit is offered, as follows : 

 Few readers, particularly in the tropics, have not had an opportunity 

 to observe how any scratch or wound on exposed parts of the body is 

 persecuted by a multitude of small flies and related insects which come 

 to sip the blood-serum, a slightly sweetish substance. One also knows 

 how, during dry periods, the margins of the eyes, for example in the 

 large mammals, are persecuted by the same impertinent Diptera, at- 

 tracted by the "aqueous humor" with which the eye-ball is moist- 

 ened. Now all these small Diptera, in common with ordinary-sized 

 one (Stomoxys, etc. ) and other large ones like the Tabanids, indicate 

 the path gone over by the hsemaphiles. The Culicids, primitively 

 only sucking sweet juices, became acquainted with animal blood 

 through the blood-serum of wounds. The males contented them- 

 selves with this, the females reached the point of intentionally perfor- 

 ating the skin to gain possession of the desired liquid. Seconded in 

 this mission by a stouter beak better fitted for piercing than in the 

 male, and thus taking advantage of the liquid so easily obtained to 



