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Immature Stages of Chalcididae


          Immature stages of Chalcididae were discussed in detail by Clausen (1940), as follows:


          The eggs of the majority of species of the family are elongated and broadest at the anterior end, with both ends smoothly rounded, and the length is four to six times tho maximum width.  A small, slightly roughened area represents the micropylar area.  In B. fonscolombei (Fig. 102B), there is a distinct slender peduncle, somewhat distended at the tip, at the anterior end.  The egg of B. compsilurae (Fig. 102A) is distinguished by the possession of a membranous envelope which conforms to the shape of the egg body but is considerably larger, and the anterior end bears a rough­ened micropylar area similar to that of the egg proper (Dowden, 1935).


          The first‑instar larvae are of two types, the hymenopteriform and the caudate.  The first‑named is found in the ectoparasitic species and in those which are endo­parasitic in lepidopterous pupae, and the caudate larva occurs among the species that develop in dipterous pupae.  The hymenopteriform larva of B.  intermedia, which is characteristic of that type, is somewhat elongate, with a large, lightly sclerotized head and 13 distinct body segments of approximately equal length, each of which, except the last, bears three pairs of sensory setae and numerous cuticular spines, particularly on the venter.  There are four pairs of spiracles, situated on the second thoracic and the first three abdominal segments.  B. femorala and E. caryobori are said to have only two pairs of sensory setae on each segment.


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                        Fig. 102


          The caudate first‑instar larva, represented by B. compsilurae and B. fonscolombei (Fig. 102C, D) has 11-12 distinct body segments followed by a tail representing one‑fifth to one‑third of the total length.  In B. fonscolombei, the tail apparently represents the fused twelfth and thirteenth segments.  There appear to be no sensory setae; but each segment bears a partial or complete ring of cuticular spines, and these occur also upon the tail, though irregularly distributed.  An internal tracheal system is present, but there are no spiracles.


          The second‑instar larva is more robust, and, in the caudate form, the tail persists, though reduced in size.  There appears to be no uniformity in spiracle number or arrangement.  B. compsilurae still has none; B. intermedia retains the four pairs present in the first instar, of which those on the mesothorax are much the largest; and B. fonscolombei (Fig. 102E), B. femorata, and E.  caryobori have nine pairs, situated on the second and third thoracic and the first seven abdominal segments.


          The third‑instar larvae show a further convergence of the two forms.  In B. compilurae, the sensory setae first appear at this time.  All species have the nine pairs of spiracles arranged as given above.  The fourth‑instar larva presents no dis­tinctive features.


          The fifth‑instar larvae of Brachymeria and Euchalcidia are oval in outline, dis­tinctly segmented, and yellowish‑white in color.  They bear no cuticular spines, but the sensory setae are present though minute.  B. fonscolombei (Fig. 102F) and B.  compsilurae parasitic in dipterous puparia and having caudate first‑instar larvae, are further distinguished from others of the family by the possession, in the mature larva, of yellowish, wedge‑shaped sclerotized plates situated just below the spiracles of the second to seventh abdominal segments.  The function of these is unknown.  The spiracles are as in the preceding two instars.



References:   Please refer to  <biology.ref.htm>, [Additional references may be found at: MELVYL Library ]