11 
A NOTE ON THE VARIABILITY IN SIZE OF 
AMBLYOMMA HEBRAEUM KOCH. 
By L. E. ROBINSON, A.R.C.Sc. Bond. 
{From the Cooper Laboratory for Economic Research, Watford.) 
(With 3 Text-figures.) 
Variability in the size and, in a lesser degree, the taxonomic 
features of male ticks, has arrested the attention of all who have had 
occasion to examine moderately large numbers of examples of the same 
species. In the case of the female tick, this variability, though doubtless 
coextensive with that of the male, is more or less obscured by the wide 
range of variation in size, depending upon the degree of engorgement; 
and, also, by the fact that in the female tick the taxonomic characters 
are, as a rule, less pronounced. The present note is only concerned 
with variability in the size of the male. 
The earhest allusion to this subject, in the published literature on 
ticks, is that of Aragao (1911), who, in the introduction to his paper on 
the ticks of Brazil, condemned Neumann’s then recently-described 
variety of Amblyomma cajennense-parviscutatum, on the grounds that 
he had observed the appearance of the parviscutatum form among the 
progeny of typical females of A. cajennense. He also noticed that such 
varieties could be produced artificially, in A. cajennense and A. goldii, 
by the forcible removal from the host, before engorgement was complete, 
of individuals in the larval or nymphal stages. Aragao also observed 
parallel examples in collections of other species of Amblyomma which 
passed through his hands, notably, fossum and braziliense. The con¬ 
dition is, therefore, generally attributable to malnutrition. 
In some notes on the genus Rhipicephalus, Warburton (1912) 
commented on the frequent occurrence of variation in size of Rhipi¬ 
cephalus males, and liis paper is illustrated ivith some striking figures 
representing pairs of males of three different species, each pair having 
been derived from a single host. 
