Notes on the Bionomics, Embryology, and Anatomy of Certain Hymenoptera Parasitica, especially of Microgaster connexus (Nees).

Abstract

Notes are given on the bionomics of certain Chalcididæ, Braconidæ, Proctotrypidæ, and Cynipidæ, especially of Microgaster cannexus, Mesochorus pallidus, and Aphidius sp. Microgaster connexus (Nees) is a Braconid parasite on the larvas of the moth Porthesia similis. Mesochorus pallidus (Brisch.) is a hyperparasite on the larvas of Microgaster which live inside the larvae of the moth Porthesia similis. Notes and descriptions of part of the life-history of Apanteles glomerulus, allied to M. connexus, are also given. Microgaster lays from sixteen to fifty eggs inside the body of small larvae of Porthesia similis. In rare cases very few eggs are laid, while in other examples sixty larvae were bred from one parasitized moth caterpillar. Average number about thirty. The anatomy of the larvae is described. My account of brain, tracheal system, gonads, silk glands, and gut broadly agrees with that of Seurat. Two tubes, called enigmatic tubular glands, are attached to the vesicle near the gut and pass up the body forwards. They do not, as described by Seurat, connect with the hind region of the gut. The heart is described; it opens into the last segment of the body, whore it is very wide. The last abdominal “segment” is expanded into an enormous vesicle, whose structure and minute histology is described. Two coiled tubes in the vesicle, described for the first time, appear to be excretory in nature. No Malpighian tubes were found, but it was thought that the enigmatic tubular glands might be modified Malpighian tubes (see pages 411–412). The gut and fat-absorption are described. The presence of food in the gut is demonstrated clearly. The hyperparasite has been shown to oviposit, while the larval Microgaster is from one-third to one-half full size. Certain facts with regard to the habits of the hyperparasite Mesochorus are given. Notes are given on Parasitism and Hyperparasitism among Aphidæ. Figures of four insects bred from Aphids, and belonging to different Families, are given. The presence of a peculiar embryonic membrane in Aphidius sp. parasitic on Aphis pomi is described, and its use pointed out. The subject of Entomophagous Parasitism in Hymenoptera is fully discussed from the point of view of Microgasteridæ and Aphidiidæ.