ON THE EVOLUTION OF DINARDA. 69 
The sooner the adaptation of Dinarda to F’. exsecta and rufi- 
barbis has taken place in a region, the more they are protected, 
through local isolation of the ants’ nests in question from those 
of allied species of Formica (especially of I’. sanguinea), so much 
the further has also the differentiation of the forms of Dinarda 
in question progressed. 
This is most clearly shown, as yet, in the differentiation of 
D. pygmea from its ancestral form dentata. 
Also as regards D. hagensi, some new facts have been added 
in the last few years, which show that its adaptation to F. 
exsecta iS not yet completed, but that in different points of its 
area of distribution it stands at different stages in the process of 
species building. Donisthorpe* found a number of Dinarda with 
F’, exsecta at Bournemouth (county of Dorset, South England), 
which comes nearer to the typical examples taken by Von Hagens 
in the Siebengebirge in 1855 than the Dinardas taken by me at 
Linz on the Rhine with the same ant in 1893-1901. Most of 
these English examples show, just as Von Hagens’s type, no 
raised keeled border to the elytra, but these organs are regu- 
larly arched, in which these examples even depart from the 
generic diagnosis of Dinarda (‘‘elytrorum margine laterali cari- 
nato’’). Also, the antenne are shorter and more compact than in 
D. dentata. On the other hand, the border of the elytra in the 
examples from Linz igs distinctly raised and keeled, and the 
antenne aresomewhat more slender than in dentata. In some 
of Donisthorpe’s examples from England transitions between 
both the hagensi forms are noticeable in that the border of the 
elytra is sometimes feebly raised, and the antenne are less com- 
pact. Dinarda hagensi has evolved, at different points of its 
area of distribution, as far as different stages towards a peculiar 
form ; further, according to the specimens found up to the 
present, it has made the greatest progress in the Siebengebirge, 
in the Rhine Provinces, and in South England, which during 
“diluvial’’ times remained free from ice, and represents the 
oldest district for the adaptation of this Dinarda to F’. eaxsecta. 
Should the process of differentiation which separates D. hagensi 
* * Dinarda hagensi, Wasm., a species of Myrmecophilous Coleoptera 
new to Britain” (Entom. Record, 1905, pp. 181-182). Donisthorpe sent me 
examples of these Dinardas. 
