1910] California Rodent Fleas 73 



The larvae upon hatching busy themselves immediately in 

 the quest for food. They experience little difficulty in locating 

 it, for at the time of birth a supply of food is found upon the egg 

 shell. Here they feed from the first on the tiny blood pellicles 

 surrounding the egg shell; this the mother furnishes when the 

 egg is laid. When the last of the egg pellicles of blood are con- 

 sumed, the insatiable worms look about them for other sustaining 

 morsels. The dejecta of the adult flea seems to provide the 

 desired ingredients. The young lar\-ae feed ravenously on the 

 bloody deposits, apparently satisfied to pass the fir.st few days 

 on this unique diet. They can subsist entirely on the bloody 

 fragments (flea faeces) when no other food is available, for a 

 period of five to six days. 



THE REACTION TO LIGHT. 



The larva is positively heliotropic up to the stage of the initial 

 moult. The more advanced sluggish larvae are repelled by the 

 light. This is seen when examining the flea breeding cages a 

 slight stirring of the nesting material attracts to the surface the 

 tiny very active larvae. If the older larvae are desired, it is 

 found necessary to nearly invert the container. Prior to the 

 final moult when the larva is in readiness to pupate it can be seen 

 almost invariably along the edges at the bottom of the box, 

 where the greatest number of cocoons are brought to view. 



TROPIC INFLUENCES IX THE ADULT FLEAS. 



Rodent fleas are negatively phototaxic (repelled by light) 

 to a very striking degree. The first impulse seeins to be to seek 

 protection from the light. This is seen in combing a squirrel 

 or rat recently killed ; the fieas will retreat constantly to the under- 

 side, alwa^^s in the direction away from the light. When shaken 

 off, they return to the shadow of the host ; in numerous instances 

 even when the animal was dead for a period ranging from 24 to 50 

 hours the fleas when shaken off would seek the host and bur^^ 

 themselves under the hairs away from the light. 



When a number of live squirrel fleas and rat fleas were placed 

 in an open test tube and held horizontally with the operator's 

 thumb covering the mouth of the vial and the bottom held 

 against the window, the fleas crowded towards the open mouth 

 in the direction of the thumb, bounding away from the window 

 in an excited manner. When the tube was reversed with the 

 open mouth towards the window, it was found unnecessary^ to 



