Immature Stages of Proctotrupidae
Immature stages of Proctotrupidae (= Serphidae) were discussed in detail by Clausen (1940), as follows:
The information on the egg and the larval instars of the Proctotrupidae (noted as Serphidae by Clausen 1940) is incomplete. The egg of the species attacking Scymnus larvae in Japan (Fig. 120A) is somewhat cylindrical, but s1ightly wider at the anterior end; the poles are smoothly rounded; and it measures 0.2 mm. in length and 0.06 mm. in width. The ovarian egg of Paracodrus observed by Zolk is somewhat elongated and measures 0.14 to 0.16 mm. in length.
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The first‑instar larva from Scymnus (Fig. 120B) is polypodeiform, and the large paired ventral processes occur on the first thoracic and the first four abdominal segments. The head is large and heavily sclerotized, bears heavy falcate mandibles, and is thus quite similar to that of mandibulate‑type larvae. The body is widest at the juncture of the thorax and abdomen and narrows appreciably to the seventh segment, following which is the apparently four‑segmented tail, which is directed dorsad almost at right angles to the body axis. The integument bears no spines or setae and is much more delicate on the tail than on the remainder of the body. There is no evidence of a tracheal system or spiracles.
The larva of Phaenoserphus viator described by Eastham is similar to the above in the essential characters, except that 10 body segments are recognizable, of which the last is much the longest and in older specimens is seen to comprise 4 segments, making a total of 13. The fleshy-paired ventral processes occur on the second and third thoracic and the first six abdominal segments and are considered to be vestigial organs. The distal portion of the tail bears vertical fin‑like projections both dorsally and ventrally.
The following instars are of normal form, lacking the large head, the paired appendages, and the tail. The third instar of P. viator may be recognized by the presence of 8 pairs of nonfunctional spiracles, whereas the fourth instar has 10 pairs, situated on the second and third thoracic and the first eight abdominal segments. Both of these instars have the labrum projecting over the mouth in the form of a rounded beak. There are no integumentary spines or setae.
The mature larva of the Japanese species (Fig. I20C) is slender and cylindrical, with i3 body segments, of which the last is small and tapers to a point. The tracheal system has the same number and arrangement of spiracles as occurs in P. viator.
The pupae of all species that have been studied have the posterior portion of the abdomen strongly curved ventrally.