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Immature Stages of Torymidae


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


The normal egg form in the Torymidae is elongate-oval to kidney-shaped, with the anterior end broadest and terminating in a short, rounded protuberance (Clausen 1940, noted as Callimodidae).  The posterior end is somewhat attenuated, and in occasional instances it terminates in a sharp point.  The egg of Epimegastigmus brevivalvus described by Noble is markedly different, for it possesses a slender stalk about 2X the length of the egg body.  The illustrations of eggs of this species in different stages of embryonic development show the had of the larva at the end of the egg opposite the stalk, and the latter must thus be posterior, as opposed to its anterior position in the normal stalked egg of the superfamily.  In this species and in Callimome cyanimum, the chorion is unsculptured and glistening, while in Ditropinotus aureoviridis (Fig. 87A), Monodontomerus aereus, Eridontomerus isosomatis, and Callimome abbreviatus it is densely clothed with minute papillae except, in some species, for a small area at the posterior end.  These papillae often give the egg a grayish color.


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The stalked type of egg described above for Epimegastigmus is of general occurrence among the phytophagous members of the family, although the stalk is normally at the anterior end.


The 1st instar larvae are hymenopteriform, with 13 distinct body segments, and bear rather large, cylindrical antennae and sensory setae on the head, heavy and long sensory setae on the body segments, particularly the thorax, which may equal the length of several segments, and spiracles on the 2nd thoracic and 1st 3 abdominal segments.  Each body segment also bears a band of short integumentary setae.


Several species show departures in one or more characters from the above.  The larva of Epimegastigmus brevivalvus is very stout, is devoid of sensory and integumentary setae, and has no spiracles or internal tracheal system.  In D. aureoviridis, there are thought to be 5 pairs of spiracles, the additional pair being on the metathorax, and there are indications of this pair in Eridontomerus isosomatis, also.


Five larval instars have been observed and described in D. aureoviridis, E. isosomatis, M. aereus, and Epimegastigmus brevivalvus.  In the first two species, the 2nd instar larvae are readily distinguished from the first by the reduction in size of the sensory setae and the absence of the bands of integumentary setae.  The sensory setae then become progressively larger and the integumentary setae more abundant in the following instars.  The full complement of spiracles appears on the 2nd instar larva, situated on the last two thoracic and the first seven abdominal segments.  In E. brevivalvus, the internal tracheal system is first evident in the 3rd instar, but open spiracles do not occur until the 5th.


The mature larva of most species bears heavy and long sensory setae and one or more rows of long integumentary setae in a band encircling each segment, giving it a distinctly hairy appearance.  In D. aureoviridis  (Fig. 87B) and Eridontomerus isosomatis, the head is also densely clothed with setae and spines of varying length.  The larva of Epimegastigmus brevivalvus bears a closer resemblance to those of the phytophagous members of the family, the integument being smooth and shining except for a transverse row of very minute setae on each segment.  That of P. pachymerum is distinguished by a heavy band of minute setae, set upon tubercles, on each segment.


In a considerable number of species, the mandibles of the 5th instar are simple, as are those of the earlier instars, but in E. brevivalvus they are tridentate, and in Megastigmus dorsalis F. and Epibootania nonvitta Gir. they are 4-dentate.



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