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Immature Stages of Dryinidae

 

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

 

          The egg and early larval instars of the Dryinidae have been described for several species, but for most of these inadequately.  The egg of Gonatopus erythrodes, as described by Fenton, is 0.2 mm long, 0.12 mm. wide, oval in outline, without sculpturing, and pale yellow in color.  That of an undetermined species of the same genus is somewhat similar, although kidney-shaped.  In G. contortulus, the egg is dark-gray in color.  Kornhauser described the egg of Aphelopus theliae as oval in form and 0.145 mm. in length.  At oviposition, several spheres accompany this egg, 0.025 to 0.035 mm. in diam., each covered with a chitinous shell that contain yolk‑like material. It is stated that these spheres, of unknown function, "are developed in the female Aphelopus from single cells in a sac‑like pocket ventral to and leading into the posterior portion of the oviduct, just below the opening of the spermatheca."

 

          The first‑instar larva of A. theliae is sacciform, or embryonic, in type, with no distinguishable organs, and the mouth parts are not sclerotized.  The embryo of A. melaleucus mentioned by Keilin and Thompson is probably the first instar.

 

          Please CLICK on pictures to view details:

                                                                                      Fig. 150

 

          The second‑instar larvae of all species which develop externally are strongly curved as a result of being enclosed within the first exuviae.  That of A. comesi is distinguished by the possession of a pair of bulbous lobes on the cephalic region, which are considered to be the mouthparts, and by the presence of nine pairs of spiracles.  The second instar of A. melaleucus (Fig. 150D) is identical in general characters, and the cephalic lobes are designated as the mandibles.  This larva also bears a heavily sclerotized pericephalic ring.  It may, in reality, be a later instar, for only three are mentioned (Clausen 1940).

 

          The third‑instar larva of G. contortulus (Fig. 150A) and certain other species is distinguished principally by a fleshy cone‑shaped process situated ventrally immediately behind the head.  The mandibles are very large and fleshy, and the pericephalic ring bears two pairs of spine‑like projections.  There are still nine pairs of spiracles.

 

          The fourth‑instar larva shows the fleshy head lobes assuming somewhat the form of mandibles.  Tho penultimate larval instar of G. contortulus (Fig. 150B), which is described as the fifth, is very robust in form and has the mesothoracic spiracles very large whereas the remaining eight pairs are small and indistinct.  In A. theliae as in other species of the genus, the pericephalic ring persists in the fourth instar; this larva, because of its prominent mouthparts, has been termed "megagnathic" by Kornhauser.

 

          The mature larvae are usually white in color, occasionally pink or green, of the normal hymenopterous form, and distinctly segmented (Fig. 150C).  Those of the genus  Aphelopus bear many integumentary spines and setae, which may be arranged in distinct segmental bands on the dorsum and sides, as in A. theliae.  In the Dryi­ninae, these spines and setae are largely lacking.  The mandibles are usually heavy and curved and may be either simple or denticulate.  There are 10 pairs of spiracles, of which the mesothoracic pair is much the largest.  In Dryinus pyrillae, there are only 9 pairs, situated on the first and third thoracic and the first seven abdominal segments.

 

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