FEATHER LICE I23 



Life History. The complete life history, from tgg to adult, takes place 

 — unlike that of the flea — on the body of the host. Not much is known 

 about this aspect of the biology of the Mallophaga. The female is almost 

 always larger than the male, and in many species the numbers of this 

 sex in any one population are greater than those of the males, and in 

 some, which have been widely collected, males have rarely or never 

 been found. The development of the egg without fertilisation (i.e. 

 parthenogenesis) is known to take place in one of the mammal lice, but 

 the extreme rarity of the males in some species and the normal apparent 

 excess of females over males, could also be caused by the immediate 

 death of the male after mating. 



The life history has been studied extensively only in the common 

 pigeon louse {Columbicola columbae)^ and most of the following account 

 refers to this species. 



The eggs when first laid are pearly white, and are fixed to the 

 feathers with a cement-like substance secreted by a special gland 

 associated with the female reproductive organs. In Columbicola and 

 other species living on the wings they are laid in rows, end to end, along 

 the grooves between the barbs of the flight feathers and under wing 

 coverts (Plate XXIV) ; in this position they are protected by the edges 

 of the grooves and so escape damage by the bill of the bird during wing 

 preening. The other main egg-laying site is on the feathers of the head 

 and neck, where again the eggs are safe from the preening bill; here 

 they are laid singly or in clusters near the base of the feather. In heavily 

 infested birds the eggs may be found attached to feathers almost any- 

 where on the body, and some of the Amblycera normally lay their eggs 

 on the feathers of the breast and belly. The curlew quill louse, like the 

 quill mite, lays its eggs in a spiral column on the inner wall of the quill. 



Each egg has a cap (or operculum), separated from the rest of the 

 tgg by a line of weakness ; any pressure applied to the egg will cause a 

 break at this point. The eggs may be objects of some beauty, adorned 

 with various reticulate surface sculpturing and plume-like processes on 

 and around the cap. The normal rate of egg-laying is unknown; a 

 female Columbicola kept in captivity at optimum temperature and 

 provided with pigeon feathers, did not average more than one egg 

 every two or three days. The time taken for incubation probably varies 

 in different species. In an incubator at a temperature of 37°G. the 

 eggs of Columbicola hatch from three to five days after laying; lowering 

 of the temperature may prolong the period to fourteen days. Nymphs 



