1928] 
A Note on the Genus Pelecinus 
209 
Although I have been pondering over the peculiar disparity 
in the sex ratio of Pelecinus for some years, it is only after 
having read Vandel’s recent paper on geographical partheno- 
gensis 7 that the significance of the matter seems clear. Vandel 
applies this term to a condition which he finds to exist in very 
diverse groups of invertebrates, where two races of a single 
species occur in different regions, the one reproducing bisexually 
and the other by a process of permanent parthenogenesis. Fur- 
thermore in the cases studied by Vandel, he found that the bi- 
sexual race is the one inhabiting the tropical part, or at least the 
warmer portion of the range of the species. There is also a 
further difference in the number of chromosomes whereby a con- 
dition of polyploidy is developed in the parthenogenetic form. 
It is quite evident that the case of Pqlecinus agrees exactly 
with Vandel’s cases of geographical parthenogenesis. The tro- 
pical forms are bisexual, and quite generally smaller in size, 
while the northern one is highly spanandrous and the female is 
extremely large. The large size of the northern race is especially 
noteworthy as it is a very large insect, particularly the female 
which may quite probably be a tetraploid form, although this 
has not been determined cytologically. 
Pelecinus is therefore most probably a further example of 
geographical parthenogenesis and extends the occurrence of the 
phenomenon to the parasitic Hymenoptera. 
7 La Parthonegenese geographique, Bull., Biol. France et Belgique, vob 
42, pp. 166-281; 1928. 
