Scanning electron microscopy of Hyposoter didymator (Hymenoptera : Ichneumonidae) in host Mythimna umbrigera (Lepidoptera : Noctuidae) larvae

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.