THE CRAB-LOUSE 81 



by the migration of the lice themselves, and this 

 doubtless does take place; but Nuttall(l) thinks 

 that spread is mainly by means of the egg which 

 becomes detached with the hair to which it is 

 cemented. The hairs of the body are continually 

 being shed and are particularly dislodged by 

 scratching. The dislodgment is not a sudden 

 process unless the hair is pulled out by force, as, 

 when loosened, it remains at first entangled in 

 the other hair and works free by a gradual pro- 

 cess. In its youngest stage the louse holds a 

 single hair, but it feeds continually so that if the 

 hair to which it had attached itself came loose it 

 would, if time were allowed, transfer itself to 

 another, the base of which was still in the skin. 

 In the older stages it holds two adjacent hairs, 

 and if one worked loose it would grasp another 

 so that it could keep its mouth against the skin 

 surface. The louse is not therefore very likely 

 to become dislodged with the loose hairs. The 

 egg, however, remains attached to its single hair 

 whether this is drawn out with force or becomes 

 detached and works free slowly. The hairs are 

 particularly liable to be shed about latrines, since 

 the sudden change of temperature causes the 

 irritation of the bites to increase and it is also an 

 opportune moment for scratching. The crinkled 

 shape of the hair makes it very likely to become 

 entangled in other hair or in the clothing of others 

 than the infested person. The lice may also be 

 spread by means of the clothing of the infested 



G 



