Morphology of the immature stages of Arge pagana (Panzer, 1798) (Hymenoptera: Argidae) with notes on its biology

•The egg chorion is reticulated with aeropyles in plant tissues, but glabrous and aporous in the exposed portion.•Male larvae have 5 instars, but female larvae have 6 instars.•The larval antennae are 1-segmented, implying its derived position.•The pupa is exarate and decticous, taking the shape of adults.

The immature stages of the large rose sawfly Arge pagana (Panzer, 1798) were investigated using light and scanning electron microscopy. The egg is partly inserted into the tissue of twigs of Rosa chinensis (Jacq.). The chorion in the plant tissue is furnished with irregular polygonal network and aeropyles, but the exposed portion of chorion is glabrous and aporous. Ten to twelve micropyles were on the posterior pole of eggs. The eruciform larva bears five pairs of ventral prolegs on abdominal segments II–VI and a pair of anal prolegs on segment X. A pair of prominent stemmata is present on the lateral side of head dorsal to the 1-segmented antennae. Male larvae have five instars, but female larvae have six instars. When fully-grown, the larvae move to the ground and spin cocoons to pupate inside. The exarate and decticous pupae are yellow, taking the shape of the adults. This species completes four generations per year, overwintering as prepupae in cocoons. The durations of egg, larva, prepupa, and pupa are 10–15, 19–24, 8–12, and 3–5 days, respectively.

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