r 
SCIENTIFIC NOTES. 93 
accuracy the area of distribution of Anopheles maculipennis in these 
islands. 
A curious fact is, that if these sausage-like sexual forms had been 
swallowed by a common gnat or mosquito of the genus Culew, they 
would have been digested and destroyed. It is only in the gut of 
Anopheles species that the parasite can undergo its sexual union and 
development—.H.J.T. 
SSCIENTIFIC NOTES AND OBSERVATIONS. 
Trina (Acroniora) psi aND T. rripens.—I have been asked to 
differentiate between the imagines of these two species. South says of 
T. tridens, Moths of Brit. Isles, Ser. 1, p. 195, in 1907, ‘I am unable 
to indicate any character that will serve to distinguish this moth from 
T. pst.” IJ think this is the feeling of most of us. Tutt, Brit. Noct. 
and their Var., in 1891, vol. 1., p.17, on the other hand, from informa- 
tion “derived almost entirely from Dr. Chapman,” goes into more 
than a page of detailed points of differentiation, at the same time he 
remarks, ‘It is well known, however, that the markings of both are so 
similar that very few Lepidopterists can separate them with any degree 
of satisfaction.” Barrett, in 1896, Lep. Brit. Isles, vol. iii., p. 245, 
says, ‘‘ The description of A. tridensis also that of A. psi so very nearly 
that the only advantageous course appears to be to point out the slight 
distinctions.” These he goes on to enumerate. In A. psi, “The 
thorax and abdomen seem to be slightly more robust and the shoulders 
a little more square ; forewing slightly broader. and more triangular ; 
the ground colour of a colder grey—devoid of either pinkish or yellowish 
tone—but varying from whitish-grey to shades very much darker than 
are observed in A. tridens. The second line of the forewings at its 
origin on the costa, runs at first more parallel with that margin, and 
so, as it bends, makes a broader and more squared curve above the 
middle of the wing. Costal spots usually rather less distinct. In the 
female the hindwings are usually more smoothly and generally suffused 
with brownish-grey, which in some instances is quite dark.” ‘ A. psi 
is also very much more variable in ground colour than the last, from a 
whiter-grey to a deep slate-grey or grey-black, but the markings are 
always distinctly deeper black and, in the vast majority of instances, the 
ground colour, whether darker or paler, is uniform.’ Nearly all these 
points appear to be of that class of difference which one sees in two 
undoubtedly rightly named series of specimens when placed side by 
side, but which when applied to separate a number of examples of the 
two species mixed together, leaves a very considerable margin of doubt, 
and a decision one always feels liable to be reversed at any time. Dr. 
Chapman, quoted by Tutt, Brit. Noct. and their Var., says, “ When you 
look for any marking apart from tint and tone, to separate psi from 
tridens, | must confess that I have been able to find none that has been 
invariable.” He also adds a very pregnant remark, “It is curious how 
similar varieties affect these species.’ Dr. Chapman refers to the 
shortness of the dagger handle in ps7, and the whiteness of the wings 
in the male, but these do not hold universally. The double mark in 
the fringe at the anal angle at the end of the dagger, exaggerated con- 
sists of two lines in pst, two blotches in tridens, but this fails frequently, 
