DEVELOPMENT OE TRICHOGRAMMA EVANESOENS. 149 
The Embryonic Development of Tricho gramma 
evanescens, Westw., Monembryonic Egg 
Parasite of Donacia simplex, Fab. 
By 
J. Bronte Oatenby, 
Exhibitioner of Jesus College, Oxford. 
With Plates 10, 11, and 12. 
Introduction. 
Since the description of polyembryony in some parasitic 
Hymenoptera by Marchal (1) the attention of a few zoologists 1 
has been turned to the interesting problems these forms 
offer. 
1 Sir Ray Lankester has kindly drawn my attention to the writings 
of the Polish Embryologist, Ganin, whose work on Platygaster, carried 
out forty years ago, is of great interest. Platygaster is a parasite on 
the larvae of some Diptera (Cecidomyia), and its larval form is curiously 
modified in early stages. According to Ganin the larva has neither 
nervous, vascular; nor respiratory systems (Compare p. 20 of this paper), 
and its last abdominal segment terminates in a curious caudal organ of 
a tree-like nature, almost certainly concerned in nutrition. The larva 
undergoes a number of moults, looses its caudal organ, and gradually 
becomes vermiform. I have lately noticed that the larva of an Apanteles 
parasitic on Porthesia has a remarkably modified ultimate abdominal 
segment, which is very large, vesicular, and formed of hypertrophied 
cells. The gut of this larva is in all the early stages completely blind, 
and the animal depends ou the swollen abdominal segment for its 
nutrition. Like Ganin’s larvae this form looses the vesicular segment 
just before pupation. It is a very remarkable fact that the ultimate 
abdominal segment should be modified for this purpose (Zeit. f. Zool., 
Bd. xv.). 
