The larval instars of Pnigalio gyamiensis Myartseva and Kurashev are described in detail for the first time. This species is a larval-pupal ectoparasitoid of Chrysoesthia sexguttella (Thunberg) (Lepidoptera, Gelechiidae), which forms leaf mines in the plant Chenopodium album L. (Caryophyllales: Amaranthaceae). The female of Pnigalio gyamiensis lays a single egg on the skin of the host larva or nearby it, without any significant preference for a particular variant. The presence of long hairs on its body provides the newly-hatched first larval instar with high mobility. Some peculiarities in this parasitoid-host relationship are described.
Keywords: Chalcidoidea; Chrysoesthia sexguttella; Eulophidae; Pnigalio gyamiensis; physiological larval functions; preimaginal morphology.