Kinsey: Gall Wasp Genus Cynips 51 
related species in nature. The existence of widespread geo- 
graphic isolation is attested in Dunn’s work on salamanders, 
in Blanchard’s studies of the king snakes, in Jordan’s studies 
of fish, in the experience of many other students of mammals, 
birds, reptiles, and amphibia, in Gulick and Crampton’s 
studies of snails, and in such work on plants as has extended 
beyond a single flora in a single geographic area. The im- 
portance of the host isolation of parasitic plants or animals 
is an outstanding feature of every study of such organisms. 
In addition every taxonomist knows that such items as sea- 
sonal occurrence, habitat, tropistic reactions, infertility, struc- 
tural peculiarities, and many other such qualities of organ- 
isms are isolation factors which would account for the occur- 
rence on occasion of more than one species of a given genetic 
stock in a given geographic area or on a given host. In spite 
of some contrary opinion (e.g. Nichols 1928), perhaps we are 
not unfair in summarizing taxonomic evidence as supporting 
a modified statement of the so-called Jordan’s Law, to the ef- 
fect that species in nature are always isolated from closely 
related species; and reflecting again on the genetic aspects 
of the situation one is inclined to postulate that before new 
species may come into existence or survive, the species must 
be isolated from the closely related species. 
Further discussion of this question must be limited in this 
place to a presentation of the data on the host and geographic 
distribution of our 93 species of Cynips. The detailed records 
and maps for each of these species are given in the systematic 
portion of the study. These data seem to lead to the same 
conclusions which we framed (Kinsey 1923) for 63 species 
of the gall wasp genus Neuroterus. In each geographic area 
there is but a single species of any phylogenetic stock on any 
given host. The wide applicability of the rule should be evi- 
dent from the summary of the host and distribution data 
which are given in the accompanying table, and the same data 
are more vividly portrayed on the phylogenetic maps which 
constitute figures 8 to 13. 
With one possible exception (C. bifur ca) every one of the 
93 species of Cynips is in a host-geographic area distinct from 
that occupied by any other derivative of the same specific 
stock. In 59 of the cases the isolation extends back to the 
subgeneric stock. This is remarkable. If our conclusions on 
