314 
Hermaphroditism etc. in Pediculus 
taming well-formed spermatozoa, or well developed operculated eggs as 
already mentioned, neither the male or female elements having any means 
of egress from the animal’s body. 
Frequency of Hermaphroditism in Pediculus humanus and its Cause. 
(a) The 'percentage observed in “ wild ” lice and other insects. 
It is impossible to calculate the general percentage of hermaphrodites 
occurring among “wild” lice because of its irregular incidence. Moreover, 
in a large number of corporis bred in our laboratory during three successive 
years and carefully examined, we failed to find a single hermaphrodite; 
subsequently we came upon 6 hermaphrodites in a very short time, but still 
later we examined 1100 specimens of the same strain with negative results. 
Among “wild” lice, certain lots, composed of about 100 to 300 specimens, 
did not include hermaphrodites, whilst other lots (see list, p. 285) comprised 
many. These lots may be divided in two groups in respect to the percentage 
of hermaphrodites contained therein: (a) Lot 273 with 8-5 per cent. (85:1000), 
and ( b) Lots 237, 257, 277, 278, giving a mean of 0-6 per cent. (6:1000) herma¬ 
phrodites 1 . This proportion of hermaphrodites, especially in group (a), is very 
remarkable when compared with the figures of Speyer (cited by Cockayne, 
loc. cit. p. 98) who reckons that the proportion of hermaphrodites is 1:30,000 
in Lepidoptera, which, of all insects examined, have yielded the greatest 
number of hermaphrodites. 
The presence of 19 hermaphrodites in Lot 273 of Pediculus humanus can 
only be compared with certain instances where numerous hermaphrodites 
were encountered in lots of Lepidoptera or Hymenoptera, instances recently 
classified by Cockayne (1915, pp. 95 et seq.) as being of a hereditary and 
familial nature. Whilst referring the reader to this author for further details, 
we may cite a case he gives (loc. cit. p. 97): “Mr L. W. Newman for some 
years bred a number of gynandromorphous Amorpha populi ; in successive 
years he bred 17, 14, 11 and 2 out of totals of 2000, 1500, 1000 and 800 
approximately. This year I have bred 3 from 500 of his pupae. This gives 
about 1 per cent, of gynandromorphs.” 
Furthermore, we may cite the celebrated case of Eugsters hive in 
Constance, to which attention was first drawn by Menzel (1862) and von 
Siebold (1864) 2 , wherein an Italian queen bee was crossed with a German 
drone and yielded hundreds of hermaphrodites during three years. Of these 
hermaphrodites, Menzel examined 30, and von Siebold about 200, the insects 
showing all grades of mixture of characters pertaining to both sexes. 
1 These percentages are given roundly. The proportion of hermaphrodites is doubtless greater 
in such cases for we must assume that dead insects were not collected. A great mortality occurs 
among hermaphrodites, especially in those of type that cannot expel their eggs or suffer from 
the prolapse of sexual organs induced by coital traumatism. 
2 Von Siebold, C. Th. (1864), “Ueber Zwitterbienen.” Zeitsc.hr. f. wiss. Zool. xiv. 78-80. 
