Superparasitism and host discrimination by Neodohrniphora elongata (Diptera: Phoridae), a parasitoid of the leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae).

The leaf-cutting ant Atta sexdens rubropilosa Forel is parasitized by several species of Phoridae flies, one of which is Neodohrniphora elongata Brown. The female of this fly oviposits inside the head of larger workers of the Atta colony, emerging only one fly from each cephalic capsule. The objective of this study was to investigate the occurrence of superparasitism by.N. elongata on workers of A. sexdens rubropilosa in the laboratory and to describe if the female of this parasitoid is able to discriminate between non-parasitized and previously parasitized workers by itself and between non-parasitized and previously parasitized workers by another female of the same species. The tests were conducted in a glass observation chamber where 15 parasitized and 15 non-parasitized workers and one fly were released at a time. The flies laid eggs preferentially in non-parasitized workers rather than workers parasitized by themselves (n=11) or parasitized by other females (n=18). In both cases females of N. elongata were able to discriminate the parasitized host, rejecting most of them, but did not avoid superparasitism. Based on the high indices of superparasitism found (29.4% ofselfsuperparasitismand49.5%of conspecific superparasitism), the process of host discrimination by N. elongata seems to be of little efficiency at least under experimental conditions.