Immature Stages of Bethylidae
Immature stages of Bethylidae were discussed in detail by Clausen (1940), as follows:
Though extensive observations have been made upon the habits of a number of species of Bethylidae, yet in few instances have the early stages been adequately described.
The eggs of the different species are quite similar, being elliptical to elongate-ovoid, 0.3-1.5 mm. in length and 2-4 X as long as wide. Usually they are slightly curved, with the anterior end broader. The chorion is smooth and glistening except in Prorops nasula, which has a granulated or reticulate surface.
The first‑instar larva of Perisierola gallicola (Fig. 147) is robust, with the segmentation indistinct. The head is large and nearly hemispherical. There are eight pairs of spiracles, situated on the first and third thoracic and the first six abdominal segments.
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The number of larval instars is known for only a few species. Williams (1919a) recorded four for Epyris extraneus and five are described for Cephalonomia gallicola and for Laelius anthrenivorus (Vance & Parker 1932).
The larval instars show little variation in their general characters. The early instars are usually indistinctly segmented and often pyriform, with only the main body divisions indicated. The third‑instar larva of C. gallicola bears a pair of long setae on the median ventral line of the first thoracic segment. The mature larvae are usually unornamented, with the integument thin and transparent. In P. gallicola, however, there is a transverse band of backwardly directed papillae on each thoracic segment, and a few fine hairs on the abdomen.
The mandibles are also an extremely variable character, though they are large and protruding in all species. In E. extraneus, they are simple in the first instar, bidentate the second, and tridentate in the third sod fourth instars, and those of the successive instars of L. anthrenivorus have two, three, five and seven teeth. In P. gallicola, they are simple in the mature larva, and presumably in the early instars also.
The number of spiracles is decidedly variable among the different species. P. gallicola (Silvestri 1923b) has eight pairs in the first instar, situated on the second thoracic and first seven abdominal segments, and on the mature larva additional pairs appear on the third thoracic and eighth abdominal segments. B. cephalotes (Richards 1932) also has eight pairs in the first instar. In contrast to this, L. anthrenivorus has a single pair on the second thoracic segment in all instars, and C.gallicola and C. tarsalis have five pairs in all instars.
The cocoons are oblong or somewhat cylindrical in form and tough and firm. In E. extraneus, the anterior end is less firm and is closed off by a neat disk, which is cut away at the time of adult emergence. The cocoons of P. emigrata and several other species are white and delicate and may be loosely woven.