358 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Not less striking is the life history of Polynema, which lays its eggs 

 in those of a small dragon-fly (Agrion virgo). The first larval stage 

 is most remarkable. It hatches as a microscopic immovable being, 

 entirely unlike any insect, with scarcely a trace of organization, being 

 merely a flask-shaped sac of cells. After remaining in this state five 

 or six days it moults. 



The second stage, or Histriobdella-like form, as Ganiu names it, is 

 more like that leach-like worm than an insect. 



The third larval form is very bizarre, though more as in insects, 

 having rudimentary antenna?, mouth-parts, legs, and ovipositor. In this 

 condition it lives from six to seven days before pupating. 



The strange history of another egg parasite (Ophioneurus) agrees 

 in some respects with that of the foregoing forms. It is when hatched 

 of an oval shape, with scarcely any organs, and differs from the genera 

 already mentioned in remaining within its egg membrane, and not 

 assuming their strange shapes. From the cylindrical sac-like non- 

 segmented larva resembling the second larva of Platygaster it passes 

 directly into the pupa state. 



A fourth form, Teleas, is an egg parasite of Gerris, and in America 

 one species oviposits in the eggs of CEcanthus. 



The spindle-shaped larva iu its first stage roughly resembles a trocho- 

 sphere of a worm rather than the larva of an insect so high in the scale 

 as a Hymenopter. It is active, but after moulting the second larva is 

 oval, still without segments. Dr. Ayers gives a profusion of details 

 and figures of the first and second stages of our Teleas, the second 

 strongly resembling the Cyclops stage of Ganin. He describes three 

 stages, and though he did not complete the life history of the insect 

 he thinks it changes to an ovoid flattened form which succeeds the 

 Cyclops stage in other Pterornalida?, and that there are at least four 

 ecdyses. 



It is difficult to account for these strange larval forms, unless we 

 suppose that the embryos, by their rich abundant food, have undergoLe 

 a premature development, the growth of the body walls being greatly 

 accelerated, the insects so to speak having been, under the stimulus of 

 over-nutrition and their unusual environment, and perhaps also the 

 high temperature of the egg, hurried into vermian existence on a 

 plane scarcely higher than that of an active ciliated gastrula. 



Further observations, difficult though they will be, are needed to 

 enable us to account for the singular prematurity of the embryo of 

 these parasites. That these stages are reversional and a direct inher- 

 itance from the vermian ancestors of these insects is not probable, but 



