Eupelminus tarsatus, Waterst. (1916).
Eupelminus tarsatus, Waterston, Bull. Ent. Res., vi, Feb. 1916, p. 389, figs. 7 and 8 ; Lamborn, ibid., vii, May 1916, p. 34.
A series of both sexes of this parasite of Glossina morsitans enables me to describe the male for the first time and the female more fully. One of the striking features about this species, apart from its remarkable sexual dimorphism, is the great range in size which it exhibits. The females run from 3½ mm. to 5 mm. and the males from 1½ mm. to 2¼ mm., with a range in the alar expanse of 2¼ mm. to 3¾ mm. The larger female examples are invariably darker and more metallic in coloration. Dr. Lamborn is certainly right in correlating the smaller size of some of the parasites with a reduced food supply (l.c. p. 35). I cannot yet agree, however, that the parasitic status of E. tarsatus is definitely fixed by our present knowledge of its habits. Plainly the proportion of Mutilla-parasitised puparia supplied to the Eupelminus females was larger than could have occurred under natural conditions. Again, the factors, whatever they are, inducing Mutilla to oviposit in a particular puparium may be equally decisive for the female Eupelminus. If, for example, in two cases three Eupelminus punctures all close together could be seen with a high-power lens one might suggest that some structural peculiarity invited the attack. Nor, incidentally, is it legitimate to infer that because a puparium observed to be stung produced no Eupelminus the attack had failed. The presumption is that the attack had not been delivered, stinging and ovipositing being, in many cases, two separate processes. Many Chalcids plunge the ovipositor into ova, puparia, etc., and then, applying the mouth to the wound, suck up the contents which have been expelled. In other cases the first stinging observed is merely the narcotising and rendering antiseptic of the host, which precedes the real introduction of the ova. The parasitic status of Eupelminus can, in fact, be settled only by examination of puparia, collected under natural conditions, from which the Chalcids have been noted to emerge.
