IN THE BRITISH ISLANDS. 17 



It would appear, from a brood that Dr. Chapman reared during 

 the summer of 1 890, that the dark forms of this species are probably 

 connected with a change of constitution (disease ?), for in the " Ento- 

 mologist's Eecord," vol. 1., pp. 271-272, he writes as follows: "I 

 have bred A. alni for several years, have always found it rather shy as 

 to breeding, and, each year, have observed several instances of useless 

 pairing. But this year (1890), though many pairings occurred, none 

 settled down in the normal manner, and no fertile eggs were laid. I 

 have called this the result of a change of constitution, not necessarily 

 disease, partly because precisely the same procedure has always occurred 

 in my hands with strigosa, and this, with moths from captured larvae. 

 The curious point, however, in the case of alni is, that in previous years, 

 hardly a specimen departed, even in a slight degree, from the normal 

 type, whilst this year, about a third of the specimens differ, more or 

 less, either in the suffusion of the pale areas with darker scales, or in 

 variation in the stigmata, generally in the direction of disappearance 

 of the orbicular one. The variation and the failure to breed may be 

 fortuitous coincidences, or there may be a causal connection between 

 them. That the latter is the case is probable, from the record of other 

 instances of a similar character." Dr. Chapman has since sent me the 

 specimens, and they are really a most interesting lot. I exhibited the 

 specimens at the City of London Entomological Society, and referred 

 to the suffused form as var. suffusa (' Entomologist's Eecord,' vol. 1., 

 p. 190). But the variation in the character of the orbicular (some 

 totally absent); and the degree of development of dark shading, and of 

 the transverse row of dots on the nervures of the hind wings, are very 

 striking. Of the 48 specimens sent, not one is really typical. 



a. var. suffusa, mihi. With the two pale patches which are 

 generally pale ashy in colour, much suffused with dark blackish-grey, 

 and closely resembling the darker parts of the wing, the specimens 

 thus appearing darker and more unicolorous. Kecorded in the 

 "Entomologist's Kecord," vol. 1., p. 190. 



/3. var. obsoleta, mihi. With the orbicular stigma entirely ob- 

 literated. I have never seen a specimen of this form except among 

 those bred by Dr. Chapman. 



Acronycta (Cuspidia) tridens and psi. 



Before entering upon the consideration of these species separately? 

 or attempting to form some comparison between them, I would remark 

 that my information has been derived almost entirely from Dr. 

 Chapman of Hereford, who has paid great attention to the genus, 

 and bred large numbers of both these species from ova. He was 

 kind enough to send me long series (79) of tridens and psi all bred 

 from ova, so that no error of determination was possible. He also 

 sent some most valuable remarks which were entirely new to me, and 

 as they probably will be to most of my readers, I shall make free use 

 of them. As is well known, typical tridens have the anterior wings 

 darker than typical psi, the darkening being due to ochreous scales 

 which are mixed with the ground colour ; the hind wings, too, k are 

 generally purer white in tridens than in psi, and less shaded with grey 



