Immature Stages of Eupelmidae
Immature stages of Trigonalidae were discussed in detail by Clausen (1940), as follows:
There is little variation in form among the eggs of the representatives of the Eupelmidae. The main body of the egg is ellipsoidal and bears a stalk of varying length at the anterior end. In A. albitarsis (Fig. 83A), this stalk is only one‑third the length of the egg body and is robust and turgid after deposition. There is no pedicel or flagellum at the posterior end, but only a minute tubercle. In other species of this genus and in other genera, the stalk is longer, at times equaling or slightly exceeding the egg body, and more slender and there is a tapering "flagellum" at the opposite end of the egg (Fig. 85A). After deposition of the egg, the stalk is usually convoluted or sharply bent. The eggs of this family are relatively large, ranging from 0.3 tb 0.7 mm. for the length of the main body.
The first‑instar larvae of the genus Anastatus are distinguished by a rather elongated form and the development of the last abdominal segment into a bifurcated process. The extreme modification in form within the genus is revealed by A. albitarsis (Fig. 83B), found in lepidopterous eggs (Clausen, 1927). The paired processes of the tail are curved and heavily sclerotized and lie at right angles to the plane of the body. The second and third thoracic and the first seven abdominal segments each bear a transverse row of long spines ventrally at the anterior margin. Those of the first row equal about three body segments in length, and they diminish in size on the successive segments. Other species of the genus show the above characters in a lesser degree (Fig. 84A), though in some the ventral spines are not arranged in a distinct row and do not appreciably exceed the dorsal spines in length.
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The larvae of Eupelmus and other genera in which the first instar is known lack the bifurcation of the caudal segment and have a relatively small number of spines. That of E. allynii (Fig. 85C) has two pairs of long spines dorsally on each body segment except the last and one pair of smaller spines ventrally on each thoracic segment. The integument is densely clothed with minute setae. In Arachnophaga, one pair of spines is dorsal and the second lateral, just beneath the line of the spiracles. The integument of the dorsum and side bears numerous peg‑like projections. The larva of E. cicadae is slender, with a large and heavily sclerotized head, and the segmental spines are very much reduced in size. That of Eupelmella vesicularis bears two pairs of long heavy spines on each body segment, with an additional shorter pair on each of the thoracic segments.
The tracheal system of this instar normally bears four pairs of spiracles, which are situated on the second thoracic and the first three abdominal segments. In Eupelmus allynii, however, an additional pair is found on the metathorax
The studies made upon Anastatus, Eupelmus, and Eupelmella indicate that there are normally five larval instars, with the intermediate and final instars quite similar in form.
In Anastatus, there appear to be two forms of mature larvae, one being that of A. albitarsis (Fig. 83D) and A. semiflavidus, in which the body is robust, almost cylindrical, curved to conform to the egg in which it develops, and bearing only a few minute setae, and the other, represented by A. disparis and Anastatus sp. (Fig. 84B), which is almost spherical in form. The latter bears short spines on the thoracic segments and a larger number on the sixth to ninth abdominal segments.
In Eupelmus, Eupelmella and Lecanobius, the mature larva is rather elongated as compared with that of Anastatus. Eupelmus allynii (Fig. 85D) bears about seven pairs of long spines on the first thoracic segment, five pairs on the second and third, two pairs on the first five abdominal segments, and three pairs on the last five abdominal segments. Those on the abdomen are considerably shorter than the thoracic spines. Among the different species, the principal variation is in the size of these spines. The mandibles are simple. The number and position of the spiracles are constant in all the known genera, there being nine pairs, situated on the second and third thoracic and the first seven abdominal segments.
There is little variation in the form of the pupae within the family. Some have the body greatly curved, to conform to the outline of the egg in which they have developed, whereas others not so closely confined are more slender and the parts of the body are in the same plane. A. albitarsus is the only species known to possess the three fleshy processes on the head superimposed over the developing ocelli (Fig. 83E).