1910] California Rodent Fleas 69 



is faintly discernible during the act as it swells and collapses. The 

 length of time involving coition in the fleas under observation 

 varied a trifle less than two hours to four and a half hours. The 

 movements preliminary to the act were not noted. 



The male makes the first effort to disconnect or disentangle the 

 pair. In one instance, the male attempted to free itself by press- 

 ing vigorously the mid and hind tarsi against the hind tibia 

 of its mate. Simultaneously, the antennae were torn from the 

 recumbent spines of the abdominal segments of the female. The 

 abdomen w^as straightened, relaxing the clutch of the claspers; 

 the spiral contracted releasing the intromittent organ, and a 

 final kick of the hind legs gave the male its liberty. The female 

 was seen on ten distinct occasions to approach the male, and the 

 latter repelled the advances of its larger companion ; at each con- 

 tact of the female, it would jump in the air, attempting to remain 

 on the opposite side of the vial. 



]\Iammalian blood appears essential for fleas to partake of 

 normal functions of copulation and oviposition. In our exper- 

 ience insects kept constantly in jars and reared from cocoons never 

 having been fed upon a host have not been observed to copulate 

 or oviposit. In thirty specimens of P. irritans taken from a house 

 which had been vacant for six weeks we found, after three days 

 observation, that the fleas were perfectly healthy; and although 

 females predominated no eggs were found at the end of this 

 period. As a control, six females of this species collected from 

 human hosts when kept in separate vials laid eggs normally, 

 depositing from 5-12 in each instance. 



Four experiments with C. actitus, the squirrel flea, have given 

 results similar to the foregoing, namely, that this species w^hen 

 reared from cocoons and kept starved in jars at room tempera- 

 ture has not been observed to mate or lay eggs. 



In twenty-five paired specimens of several species kept under 

 observation it appears that the male does not long survive the 

 act of mating. It dies even before the female has laid its first 

 batch of eggs. When fertile females are kept under artificial 

 conditions the eggs are laid in one laying in a period beginning 

 two hours after copulation and extending to a maximum of 

 thirty-six hours. When deprived of food the female has never 

 been observed to oviposit after this length of time. 



We may note here that when used experimentally the female 

 is invariably longer lived. Experiments to determine length of 



