NECESSITY OF BLOOD AS FOOD 277 



RELATION OF FOOD TO OVIPOSITION. 



Finlay found that the female Aedes calopus could not develop its eggs without 

 having obtained blood. " Nearly all the females captured after having filled 

 themselves with blood, at the end of a few days lay eggs, while those which are 

 fertilized and have not been able to obtain blood die without ovipositing." He 

 believed furthermore, as calopus does not lay all its eggs at once, that it needs 

 several blood meals to dispose of all its eggs. 



Eeed and Carroll confirmed the observations of Finlay and found that the 

 interval between a blood meal and oviposition may vary from two to thirty days. 

 " As a rule, the eggs are laid within seven days ; sometimes a second or third 

 meal of blood is taken before any eggs are laid." 



The French commission also found that in calopus blood food is indispensable 

 for the reproduction of the species. They found that whether the female sucked 

 blood before or after copulation the eggs would be deposited within a few days. 

 If a fertilized female is fed on sweet substances the eggs will not develop; if 

 afterwards, for example after 15 or 20 days, the female is fed blood the eggs 

 will then develop. In the latter case the interval between the blood meal and 

 oviposition vnll be about the same as when it has fed on blood soon after being 

 fertilized. In one of their experiments 10 females and 15 males were placed to- 

 gether in a cage on the same day that they had issued from pupas. Three of the 

 females were taken out 48 hours afterward and induced to suck blood. Of these 

 three females one deposited eggs after four days, the other two after six days. 

 After 18 days three of the females which had been fed only upon honey, and 

 which had not oviposited, were allowed to suck blood ; they deposited eggs five 

 days after the blood meal. The four remaining females which had not been 

 allowed to suck blood died without depositing eggs. The French observers state 

 that the result is the same whether the females are allowed to bite man or some 

 other warm-blooded animal, but that it must be remembered that calopus shoM^s 

 more or less repugnance towards any other animal. 



Goeldi, at Para, made a series of experiments with similar results. One of his 

 conclusions is that blood food, in hastening the development of the eggs, shortens 

 the life of the mosquito. On the contraiy a diet of honey prevents the develop- 

 ment of the eggs and thus prolongs life. He found that by feeding the females 

 with honey the power of depositing fertile eggs may be kept latent for long 

 periods. He determined, also, that unfertilized females would lay eggs when fed 

 with blood but that these eggs would not produce larvae (pseudo-partheno- 

 genesis). Goeldi found that the interval between the first blood meal and 

 oviposition averaged 3.7 days = 88 4/5 hours. The female, after having de- 

 posited all her eggs, dies, either immediately afterward or at the most within a 

 few days. The longest time that a female survived oviposition was 14 days. 



Goeldi determined that the shortest interval between a blood meal and ovi- 

 position was two days, the longest interval seven days. He gives observations in 

 which eggs were laid one day after a blood meal, but in these cases the females 

 were captured and probably had already sucked blood. On one occasion, in an 

 experiment with captured females, eggs were laid after blood had been withheld 



