ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 51 



exception of rearing on pigs, there is no record of successful raising of 

 PecUculus humanus except on man. 



There is notable variation in the proportion of the sexes in the 

 offspring of different parents. There are broods in which one sex pre- 

 dominates. Oviposition lasts 17 seconds at most. The female walks 

 backwards along a hair, which glides within the fork formed by the 

 posterior lobes of the last abdominal segment. The gonopods are flexed 

 away from the body and against the hair, gripping it ; a minute drop of 

 hyaline fluid is exuded ; the egg is liberated and cemented ; the female 

 releases her grip with the gonopods and moves forwards. Full details 

 are given. A female in optimum natural conditions may lay 9 to 12 

 eggs a day, 275 to 300 in all. There is, especially in corporis, a marked 

 tendency to oviposit where eggs have been previously laid. Unferti- 

 lized eggs may be laid, but they do not develop. 



The eggs of corporis do not hatch at 22" C, or below ; the development 

 is about 16 days at 25° C, 5 to 6 days about 36^-37''; they die without 

 hatching at 40°-45° C. The eggs of capitis on the wrist at 32°-35°C. 

 hatched in about 7 days. 



An account is given of the obvious changes within the egg, the 

 emergence of the larva, and the moults. The development from egg to 

 egg may be passed through in about 17 days— 7 in the egg, 4 in the 

 first larval stage, 3 in the second, 2 in the third, and 1 day before ovi- 

 position. A lemale may have 1918 descendants during her lifetime, 

 and the offspring of her daughters, during their hfetime, would number 

 "■ 112,778 — 48 days after the original female began ovipositing. A female 

 may live up to 30 days at 28° C, if fed once daily; 45 days, if fed twice 

 and kept at 24° by day and 34° by night ; witli more feeding a male 

 may live 32 days and a female 46. AVhen kept continuously on the 

 wrist, a male may live 23 days, a female 22 days. 



Descriptions are given of the mode of feeding, the gorging when 

 very hungry, the reactions to various stimuli, the " sham death," and 

 many other interesting details of behaviour. 



Notes on Lice.* — F. M. Howlett found in India that specimens of 

 Pediculus capitis bred on the body showed in the second generation a 

 modification of chitinization and colour in the direction of P. corporis. 

 Previous experiments with an unidentified species of Culex showed that 

 a warm surface stimulated the female to bite. The proximity of a hot 

 body (e.g. a warmed comb) stimulated rapid and excited movement in 

 Pediculus and Phthirus, which made for the warm surface. 



Philippine Derbidse.f — Frederick Muir reports on large collections 

 of these delicate little insects (Rhynchota), and brings the Philippine 

 list up to ninety-eight species in thirty-nine genera. Many of the species 

 have been erected on characters of the male genitalia, e.g. the form of 

 the pygophor, anal segment, and genital styles. The eggs of Derbidaj 

 have never been described, and the author has failed to find them. 



* Parasitology, x. (1917) pp. 186-8. 



t Philippine Journ. Sci., xii. (1917) pp. 4C-10i (1 pi. and 4 figs). 



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