Melanagromyza chalcosoma

Melanagromyza chalcosoma Spencer, 1959

M. chalcosoma is distinct because of a greatly enlarged ocellar triangle and a generally broad frontorbital area. This character is only shared by Melanagromyza obtusa which can be only separated by the geographical range and slight behavioural differences: In contrast to obtusa, chalcosoma pupates within the seeds rather than in the pods outside the seeds. Most probably obtusa does not occur in Africa.

Wing length: about 1.8 mm. In contrast to obtusa the frontorbital setulae are partly proclinate.
However, the material of chalcosoma studied in the Natural History Museum London (BMNH) by the author shows a considerable variety in surface structure and other external characters.
Male terminalia
Male aedeagus similar to that of Melanagromyza obtusa: Hyaline, basiphallus with unusual long side arms, which are extending up to the distiphallus.
Immature stages
Posterior spiracles lacking a central horn, there is only a weak thickening visible.

BIONOMICS (Koehler and Metha, 1971)
The adult fly deposits eggs through the wall of the developing pod. The larva feeds within a single seed, pupates there and emerges as an adult, commonly leaving its puparium within the seed. Attack results in a tiny cylindrical cavity extending entirely through the long axis of the seed. Emergence of adults occurs within a week or two after the pods mature and begin to dry. No further infestation by this species takes place after the seeds have dried.
The only known biological difference to the related species Melanagromyza obtusa is that chalcosoma pupariates directly within the seeds instead of leaving them to pupariate in the pod.

Cajanus cajan (pigeon pea), Flemingia rhodocarpa Bax., Vigna unguiculata (L.) Walp. (cow pea).

Africa: Known from Kenya, Malawi, Tanzania and Uganda.
BMNH-material: Nigeria, Mauritius, Zanzibar.

Larval feeding left not much visible damage on the seed but certainly a seed inhabited by the agromyzid fly is unsuitable for human consumption. Moreover, the fertility and vigor of cowpea seeds used for sowing is reduced (Koehler and Metha, 1971).
In the countries of occurrence, Melanagromyza chalcosoma belongs to the group of major pests of pigeon peas (Minja et al., 1996, 1999).