The eggs of Rhodites are fixed to a long stalk thickened at the end; those of Inquilines and certain Chalcids (Leucospis gigas, Fig. 489, A) are also stalked; and the use of this stalk in the eggs of Cynips (E) is thought by Adler to be respiratory, while, also, he states that the egg-cavity communicates with the egg-stalk, so that a part of the egg-contents can pass into the latter, and this happens at the laying of each egg. The egg of certain ichneumons (Paniscus, Fig. 488) ends in a short stalk, which is inserted in the skin of the caterpillar destined to serve as the host of the parasite, the eggs, as stated by De Geer, being retained more firmly in the integument by the stalk so swelling as to form two knobs (Fig. 498, c).
Fig. 488.—Young larva of Paniscus in position of feeding on the skin of a caterpillar: a, the egg-shell.—After Newport, from Sharp.
Certain Homoptera also have stalked eggs, as those of Psylla pyricola (Fig. 489, B), those of Aleyrodes citri (C, a, b), and of an allied form, Aleurodicus cocois (D), and those of Corixa (Fig. 493).
Fig. 489.—Stalked eggs: A, of a Chalcid (after Fabre); B, of Psylla (after Slingerland); C, of Aleyrodes; D, of Aleurodicus (after Riley and Howard); E, of Dryophanta scutellaris (after Adler).
Fig. 490.—Eggs of ox bot-fly, enlarged.—After Riley.
Reference should also be made to the eggs of lice, which are oval and attached to the hairs of their host. Those of the ox bot-fly (Hypoderma lineata) are usually placed four to six together, and fastened to a hair. The lower portion of the egg is admirably adapted for clasping a hair. “It consists of two lobes, forming a bulbous enlargement, which is attached to the egg by a broad, but rather thin, neck, so that, when the latter is viewed sidewise, it appears as a slender pedicel” (Fig. 490, a-d). (Riley in Insect Life, iv, p. 307.) The egg of another fly (Drosophila ampelophila, Fig. 491) bears a pair of long, slender appendages near the anterior end. “The egg is inserted into the soft pulp of the decaying fruit; these appendages leave the ovipositor last, and are spread out upon the surface of the mass. They, in this way, serve to keep the egg in place, and thus insure the emergence of the larva into the open air instead of into the more or less fluid mass in which the egg is situated. The larva issues from the egg just above the base of these appendages.” (Comstock.)
