GENEALOGY OF INSECTS. 
295 
GENEALOGY OF THE INSECTS (HEXAPOD A). 
X. Hymenoptkra. 
IX. LKI'IDOI’TEHA. 
\ 
I. Tiiysanuha. 
(Camp odea.) 
GENEALOGY OF THE HEXAPODA. 
I. Thysanura . — This order once comprised some lost types nearly re- 
sembling Lepisma, Campodea, and Japyx, and more especially Scolopeu- 
drella, the probable stem-form of the Hexapoda. In other words, from a 
hypothetical form resembling Campodea or Scolopendrella, it is not diffi- 
cult to suppose that all or at least the majority of Hexapoda took their 
origin. It is possible that by a few intermediate steps now lost, Forfi- 
cula may have descended from the Thysanuran Japyx ; this is suggested 
by the form of the body, the head with its Y-shaped suture, and the ab- 
domen with its forceps, so like that of Japyx. The genus Lepisma is a 
rather more specialized form than Campodea, and Machilis is still more 
so, as proved by its mouth parts and the presence of compound eyes. 
Scolopendrella, with its abdominal true legs, comes nearer to our hypo- 
thetical form than even Campodea. The group of Poduridce (Collem- 
bola) is most probably a series of degradational forms, originally sprung 
from a higher, more generalized, Cainpodea-like ancestor. 
II. Dermatoptcra . — This order, represented by but one family, differs, 
as already stated, from the Ortlioptera, with which it is usually classi- 
