69 



Waterston (J.). A New African Louse {Polyphx calva, sp. n.) from 

 Cricetornys.—Parasilologij, Cambridge, ix, no. 2, 26th February 

 1917, pp. 199-202, 2 figs. 



A description is given of this new species from specimens taken on 

 Cricetomi/s gambianus at Accra and in Zanzibar. 



Bacot (A.). A Contribution to the Bionomics of Pediculus humanus 

 {vestimenti) and Pediculus capiiis. — Parasitology, Cambridge 

 ix, no. 2, 26th February 1917, pp. 227-258, 4 figs. 



This paper describes experiments carried out with a view to solving 

 certain problems relating to sex and fertility of lice and incidentally 

 to obtain further evidence on the laying and hatching of their eggs. 

 It was originally intended to deal with Pediculus humanus only, but 

 P. capitis was ultimately included in the experiments also. The 

 method of conducting the experiments was similar to that adopted 

 by Sikora [see this Beview, Ser. B, iii, p. 226], the insects being kept 

 under as natural conditions as possible. 



P. huniamis is a larger, more robust and less active species than 

 P. capitis, the females having a relatively greater egg-carrying capacity. 

 In the experiments described, the eggs were larger and the number 

 laid was greater than in the case of the smaller species. Cross pairings 

 were easily effected, the offspring being fertile ititer se. Hybrid strains 

 were produced until the F. 3 generation, and presumably could have 

 been carried on indefinitely. The author considers that the marked 

 disparity in the sexes of the F. 1 generation of some of the crosses 

 suggests that P. capitis and P. humanus are specifically distinct, 

 though no such obvious disparity occurred between the sexes of the 

 F. 2 and F. 3 hybrid generation. The female of P. humanus was found 

 to lay as many as 295 eggs, while the record for P. capitis was 141, 

 these figures probably being exceeded under natural conditions. 

 Experiments proved that fecundity is dependent on feeding, though 

 the fertility of the eggs laid was not affected by increased food. The 

 longevity of the male of P. humanus was about 32 days in these 

 experiments, the longest female life being 46 days, with an average 

 of 34 days. For P. capitis the figures were : male, 30 days, female, 38 

 days, with an average of 27 days. Whether the length of life would 

 be extended by unrestricted feeding remains to be proved. Tests 

 made with unfed P. humanus showed that at a temperature of 60° to 

 65° F., many individuals lived from 3 to 4 days, while at 75° F., all died 

 within 5 days, and at 98° F. all died within 3 days. Newly-hatched 

 larvae, unless fed, lived less than 24 hours at 98° F. Active specimens 

 of P. humanus survived two days at a temperature of 27° to 30° F., 

 but none survived a week. Under humid conditions, at 88° F., 3 per 

 cent, of the eggs hatched on the 7th day, 56 per cent, on the 8th, 

 8 per cent, on the 10th, and "2 per cent, on the 11th. No eggs 

 hatched at 60° F. while at 77° there was considerable egg mortality. 

 At 99° hatching was spread over 5 days and the mortality was not 

 excessive. A single female may have 4,160 descendants during 

 her life. 



