The " polyembryonic " development of an Encyrtus, as studied by P. Marchal, is highly remarkable.
A similar specialization has been observed by Marshall Ward in the Puccinia parasitic on species of Bromus, and by Neger, Marchal and especially Salmon in the Erysiphaceae.
P. Marchal has (1904) described this power in two small parasitic Hymenoptera - a Chalcid (Encyrtus) which lays eggs in the developing eggs of the small moth Hyponomeuta, and a Proctotrypid (Polygnotus) which infests a gall-midge (Cecidomyid) larva.
Marchal points out the analogy of this phenomenon to the artificial polyembryony that has been induced in Echinoderm and other eggs by separating the blastomeres, and suggests that the abundant food-supply afforded by the host-larva is favourable for this multiplication of embryos, which may be, in the first instance, incited by the abnormal osmotic pressure on the egg.