Ophiomyia spencerella (Greathead, 1971)
Material: BMNH
This exclusively African bean fly is very similar to Ophiomyia phaseoli but the aedeagus is distinct.
IMPORTANT CHARACTERS
Adults
Wing length: 1.8 - 2 mm. Frontorbital setae situated irregularly, standing in groups of 2-3; sometimes 1 frontorbital seta proclinate.
3-.. abdominal tergites polished.
1st halves of abd. tergites dark reddish or brownish, 2nd halves black.
Male terminalia
Visible part of hypandrium short with rather thin frame that is somewhat thickened just below the epandrium. Hypandrial apodeme present. Ejaculatory apodeme large, longer than hypandrium, strongly asymmetrical. Tip of epandrium projecting, covered with long hairs.
Sclerotized parts of the basiphallus rather broad, distiphallus as in Oph spencerella aedeagus.pct.
Immature stages
Posterior spiracles with raised stalks and a highly variable number of spiracular bulbs on each spiracle.
BIONOMICS
The live cycle appears to be similar to the closely related species Ophiomyia phaseoli, but detailed ecological studies on Ophiomyia spencerella are rare. The following description is mainly based on Greathead, 1968. Unlike phaseoli the females of spencerella lay their eggs mainly into the hypocotyl of the stem, near the ground level, but rarely into leaves. Nevertheless the leaves are regularly punctured by the females to obtain food.
Although the larva hatches not in the leaves, the lifestyle is not extremely different to Ophiomyia phaseoli: They mine near the midrib to the petiole and enter the stem or the junction between stem and petiole. The larva hatching in the hypocotyl, feeds downwards into the hypocotyl and taproot and returns to ground level or above, where pupation takes place.
HOST PLANTS
Fabaceae: Lablab purpureus, Phaseolus lunatus, Vigna mungo, Vigna umbellata, Vigna unguiculata. The main host seems to be snapbean (Phaseolus vulgaris).
DISTRIBUTION
As far as known confined to Central and Southern Africa, records exist from Kenya, Malawi, Mozambique, Nigeria, Rwanda, Tanzania, Uganda and Zambia. (among others Talekar, 1990).
ECONOMIC IMPORTANCE
In Africa, where Ophiomyia spencerella occurs together with Ophiomyia phaseoli is probably at least as serious as the latter species. Greathead, 1969 concluded, the species can cause heavier damage in the root system than phaseoli because the larvae generally feed closer to the root. The ratio of abundance between phaseoli and spencerella was shown to be variable (Songa and Ampofo, 1999).