Structure and function of the exocrine glands of the genitalia of females of the two-spot ladybird, Adalia bipunctata (Linnaeus, 1758) (Coleoptera: Coccinellidae).

In females of Adalia bipunctata (LINNAEUS, 1758), there are exocrine glands associated with the coxites that form part of the genitalia. The coxites are extended anteriorly in the form of a gutter with the concavity orientated towards the vagina. The edges are continuous with a shiny membrane that forms a coxal reservoir. The concave side of this gutter-like extension is lined by a layer of glandular cells. Their ultrastructure is typical of the type 1 insect epidermal cells of NOIROT and QUENNEDEY (1974). The coxal cells undergo a three stage activity cycle that is synchronised with the ovarial activity and correlated with ladybrid age. The huge development of the smooth endoplasmic reticulum in the third stage of the activity cycle indicates that terpenoid substances are produced. On the basis of behavioural observations we suggest that these exocrine glands have a role in the sexual behaviour of A. bipunctata although we cannot exclude a role in the chemical protection of eggs.