FOOD AND FERTILITY 25 



maturation of her ova. Under natural conditions 

 it must be very rare for virgin females to suck 

 blood. As soon as the female mosquito has mated 

 with the male she develops a sudden craving for 

 animal blood. The haematophagus habit appears to 

 be dependent on the presence, in the female, of the 

 spermatozoa of the male. This statement also has 

 been called in question. But of all the mosquitos 

 dissected, among those actually caught in the habi- 

 tations of human beings, which contained blood in 

 their stomachs, not one was found that did not 

 have living spermatozoa inside her spermathecae. 

 From this it must be inferred that virgin females do 

 not, commonly, take blood ; in captivity, perhaps, 

 if they are starving the unfertilised female may be 

 induced to pierce the skin with her proboscis. It 

 is interesting to try to conjecture the nature of the 

 changes, within the female, caused by mating with 

 the male, which induces such an alteration in her 

 dietary. In several small animals and insects for 

 example, tadpoles and caterpillars food is an im- 

 portant factor in the determination of sex. The 

 well-known case of the honey-bee may be quoted. 

 Here sex is determined by fertilisation, the males 

 originating from unfecundated eggs by partheno- 

 genesis, while the fertilised eggs produce the females. 

 Then the food of the larva determines whether 

 these females become barren workers or the queen 

 bees. In the mosquito, however, the sexual factor 

 determines the choice of the food Nature appears 

 to have reversed her procedure. 



