BREEDING TECHNIQUE 467 



have not fed since they emerged from the cocoon will survive Jonger 

 than those in which adult life has properly commenced. Specimens 

 removed from the host and kept in glass tubes usually die in a few 

 hours. 



The following method for breeding the fleas of small animals is at 

 once simple and effective. The animal is either caught in a wire 

 trap, or subsequently placed in it, together with its 

 nest or some soft hay or other debris, and the whole nan\ou\ tin 

 is wrapped round in a large piece of stout white 

 cloth, tied up at the top. Food is introduced through the door of 

 the trap. Any urine passed by the animal is at once absorbed by the 

 cloth, so that the surroundings are always kept dry. Faeces will 

 usually pass through the bars, and can be removed. When the cloth 

 becomes dirty the cage and all the debris under it are lifted up and 

 removed to a clean one. The eggs of the flea are laid on the cloth, 

 and the larvae make no attempt to move away, and can at any time 

 be picked out from the debris under the cage. If it is desired to 

 examine the animal closely it can be removed by hand through the 

 door of the cage, taking the precaution to wrap the hand in a piece 

 of cloth. This method has the great advantage that the material 

 under the animal never gets sodden with urine. The fleas never 

 attempt to leave the host. For exact experiments the possibility of 

 other fleas reaching the animal from outside can easily be guarded 

 against. 



Fleas may also be bred in larger cages fitted with a lattice-work 

 false bottom, on which the host rests. Under this is placed a tray 

 of sand, previously sifted and cleaned, and if necessary sterilized by 

 heat to kill off any eggs which may be present. The females leave 

 the host to oviposit in the sand, from which the larvae and pupae 

 may be obtained. In searching for larvae one may either rake the 

 sand with a needle, when they will betray their whereabouts by their 

 movement, or else spread out a quantity of the sand on a large sheet 

 of white paper and examine it, if necessary, with a hand lens. If the 

 sand is spread out in a thin layer the larvae leave a track behind 

 them as they move about, thus rendering detection easy. Pupae may 

 be collected from the sand under the host by passing it through a 

 fine sieve ; or they may be found in little heaps, the cocoons adhering 

 together, in corners of the tray. 



Larvae should be picked up with a small moist brush, never with 

 forceps. 



