Notes of the Ancestry of the Coleoptera® 
BY G. C. CRAMPTON, PH. D. 
There are three principal theories concerning the probable nature of the ancestors 
of the Coleoptera. In one of these, it is maintained that they were like Neuroptera, 
in another it is maintained that they were like Blattids, and in a third, it is main- 
(ained that they were like Dermaptera. 
The chief reason for assigning the Coleoptera a position near the Neuroptera is 
that both groups exhibit a complete metamorphosis, and since the Neuropters are 
considered to be the mest primitive of insects with complete metamorphosis, they are 
regarded by many as the nearest living representatives of the ancestors of holometabo- 
lous insects, ineludiag the Coleoptera. The nature of the metamorphesis exhibited 
by the two groups, however, is not adequate evidence for placing them near together, 
unless a study of the comparative anatomy of the two orders would bear out such 
an assumption, since a complete metamorphosis occurs in some Hemipteroid insects 
(Coccide) and not in others, and its presence or absence is therefore not sufhcieat 
proof of relationship unless supported by the evidence of comparative morphology as 
well. If both Neuroptera and Colecptera are ultimately to be traced back to Plecoptera- 
like forbears (as seems to be the case) it is possible to maintain that tendencies 
present in the Plecopteroid stock (such as the rather marked difference between the 
nymphal and adult forms apparent in certain Plecoptera) could reappear and find 
opportunity for greater development in two distinct lines of descent ultimately derived 
from such a common stock, if both were subjected to similar environmental or selec- 
tional influences. The similarity between larval Coleoptera and Neuroptera in the 
nature of their thoracic sclerites and other structures has been referred to in an article 
recently published in the Proceedings of the Entomological Society of Washington; 
but, as I there stated, other structural similarities between the Coleoptera and _ the 
members of the group to which the Dermaptera belong would greatly outweigh the 
above mentioned resemblances between the Coleoptera and Neuroptera. 
Some of the lower Coleoptera such as the Lampyride, ete, have broad pronota 
and flattened bodies bearing a superficial resemblance to certain Blattids; and, since 
there is a marked tendency toward a thickening of the fore wings to form tegmina 
in the latter group, this is taken as evidence of the ancestral nature of the Blattids 
by certain investigators who would seek to derive the Coleoptera from Blattoid an- 
cestors. On the other hand, a comparison of the anatomical structures of the Coleop- 
tera with those of the members of the group next to be considered (the Panplecoptera), 
has brought to light similarities so much more profound and far reaching (even 
with regard to the minuter details) that I have become convinced that the closest 
afhnities of the Coleoptera are with the members of the group in question, and that 
the Dermapteron representatives of this group approach extremely closely to the Coleop- 
tera in their lines of devlopmnt. The Dermaptera alone, however, have by no 
means retained all of the ancestral features present in the forebears of the Coleoptera, 
“Contribution from the Entomological Laboratory of the Massachusetts Agricul- 
tural College, Amherst, Mass. 
