F. Bahena et al., Scanning electron microscopy of Hyposoter didymator (Hymenoptera : Ichneumonidae) in host Mythimna umbrigera (Lepidoptera : Noctuidae) larvae, ANN ENT S A, 92(1), 1999, pp. 144-152
Hyposoter didymator (Thunberg) is an ichneumonid solitary and nonparalyzing
parasitoid of noctuids of agricultural importance, native to many Spanish
regions, that develops internally in the host until the last instar exits t
o pupate in a silken cocoon. Larvae of one of its hosts, Mythiumna umbriger
a (Saalmuller), were parasitized by this ichneumonid, and the morphology of
eggs and lanae of the wasp were examined under the scanning electron micro
scope. The current study revealed that tills ichneumonid had a typically hy
menopteriform egg with smooth chorion and 3 larval instars with a clear het
eromorphosis. The 1st instar was of a caudate type with a caudal appendage
as long as 1/3rd of the total body length, weakly defined triangular head,
and suctorial mouthparts with no visible mandibles. The 2nd instar was a tr
ansition stage with a reduced tail-like caudal segment, a semispheric head
that was partially embedded in the thoracic segments, and suctorial mouthpa
rts with conic-shape inner mandibles. The 3th and last instar was typically
hymenopteriform, with 13 dorsoventrally compacted segments, vestigial caud
a, and inner mandibles. After the larva exited from the host, antennae were
not present, but 2 roundish stemmata, production of silk, and papillae-lik
e structures covering the integument with a regular disposition were discer
nible. Encapsulation of parasitoid eggs was also observed and described at
different time intervals after parasitization.