14 Dana on the Classification of Animals 
under the former (the Dipters) have the posterior wings obso- 
lescent, and those under the latter (Strepsipters) the anterior. 
Insects of tlie first of these grand divisions are eminently 
pterosthenic or strong in the wing—Hymenojfters, Dipters, Lept- 
dopters and Neuropters being relatively good flyers. Those 0 
the second are as decidedly podosthenic—Coleopters, Hemipters 
and Orthopters being relatively poor flyers, and strong in the Jeg. 
Consequently the terms Pterosthenics and Podosthenics might be 
employed for the two grander divisions of Insects, as well as for 
those of Birds (Art. I, p. 343). Yet their use in the two cases 
would be different; for in Birds the wings and legs are relatively 
anterior and posterior members, and not dorsal and ventral as 1m 
nsects. But since the dorsal and ventral parts have a similar 
opposite relation to the systemic centre as the anterior and 
posterior, as just now remarked, the difference is one of degree 
rather than of kind. 
As there are pteroprosthenic and pterometasthenic Insects, sO 
there are podoprosthenic, or those in which the anterior legs are 
stronger than the posterior, and podometasthenic, or those m 
The Thysanures or Apiers, which constitute the third grand- 
division, are urosthenic, most of the species having even the 
the names in the synopsis are added only the two characteristics 
of (1) perterrestrial (terrestrial in both larval and adult life) ot 
semiaquatic (aquatic in larval life), and (2) permaturative or pre- 
uturative. 
I. Ptero-prosthenics, or Ctenopters. 
i. Apirens (from Apis bee and penna wing, the wings being 
approximately like those of the Bee). 
; Hi; menopters.—Perterrestrial. Permaturative. 
b. Dipters.—Mostly perterrestrial. Permaturative. 
ce. Aphanipters (Fleas).—Perterrestrial. Permaturative. 
- ? As the anterior pair (or that which is obsolescent in th Strepsipters) is of little 
functional value in the Pterometasthenics, t i ot of es or four- 
Winged among them is of much less importance than among the Pteroprosthenics. 
Moreover, there is a line of gradation from ordinary Coleopters to the Strepsipters 
