Dear Ade Efin, My compliments for y

Dear Ade Efin,

My compliments for your high quality photographs. What kind of equipment did you use?

The size of the head width of your specimen, 1.9 mm, would place it in the Tetragonula species complex of hirashimai-geissleri-melina-sarawakensis-testaceitarsis-valdezi-zucchii.

However, melina and sarawakensis belong to the so-called bicolorous group, having more or less extensive brownish to yellowish body parts among blackish parts, whereas your specimen appears to be black throughout (only part of the extremities, viz the scape and coxae, appear to be less dark, somewhat brownish). So they do not fit.

Also unlikely are hirashimai and geissleri, both somewhat larger than your specimen. That leaves testaceitarsis-valdezi-zucchii as most likely species. In such cases of very similar species I put much emphasis on geographical distribution. We have to rely on type locality since so little is known. Tetragonula testaceitarsis (Cameron) was described from S Thailand, T. valdezi (Cockerell) from Singapore, and T. zucchi Sakagami from C Peninsular Malaysia.

The best bets are valdezi and zucchii, so your suggestion of the latter is good. One problem with zucchii is that its nest entrance is described (Sakagami, 1978) as somewhat funnel-shaped, the margin bright yellow, hence apparently quite different from your photograph. So as a first approach I would suggest that the best identification of your specimen is T. valdezi-zucchii species complex.

Your next steps should include the measurements of the head width of more specimens, at least 10, chosing the largest and the smallest. From your photographs I cannot see the tarsi nor the mandibles. Very important are also the male genitalia, so try to collect males. Shape of nest entrances are also important, so try to find more to check the variation. Presumably you can easily collect many specimens, so you may consider sending me one or two for close inspection. Photographs alone are not reliable, especially in such difficult taxa.

Hoping to have been of some help, I remain with best wishes

Hans