Читать книгу A Text-book of Entomology - A. S. Packard - Страница 23

This mode of formation of the head may be observed still more easily in Rhodites, Hemiteles, and Microgaster, from the fact that their oculo-cephalic buds are much more precocious, and that the eyes are charged with pigment at a period when the insect still preserves its larval form.

“... I believe that this mode of formation of the head occurs in all Hymenoptera with apodous larvæ, in this sense; that a more or less considerable part of the first thoracic segment is always soldered to the head of the larva to constitute the head of the perfect insect. The arrangement of the nervous system is naturally in accord with this peculiarity of development, and the cephalic ganglia of the larva to which the ocular blastems later adapt themselves, are found not in the head, but in the succeeding segment (Figs. 39, 40, 41).

“Relying on these facts, I maintain that the encroachment of the head on the prothorax is a consequence of the preponderance in size of the brain, and indicates the superiority of the Hymenoptera over other insects....”

That the pronotum is derived from the larval prothoracic segment is proved by the fact that the first pair of stigmata becomes what authors call the “prothoracic” stigmata of the perfect insect. But Bugnion thinks that the projection which carries it, and which he calls the shoulder (Figs. 41 and 42), belongs to the mesonotum.