TTTT TNTRODFOTTON. 



small grey typical form of Agrotis ripce appears to be almost confined 

 to the Lincolnshire coast. Many other species might be mentioned 

 varying in size according to locality and environment. But where any 

 species abounds, many specimens may usually be taken both above and 

 below the normal size. Such variation may then be due to heredity, 

 or what appears to me more probable, to the partial failure of the food 

 supply in the larval stage. I have very small specimens of Leucania 

 phragmitidis, Caradrina morpheus, Agrotis tritici, A. puta, A. valligera,A. 

 suffusa, Calamia lutosa, Gortyna ochracea, Hydrcecia micacea,Noctua rubi 

 and others. 



In shape, some specimens exhibit considerable variation. I have 

 a number of Agrotis tritici in my cabinet, with the fore and hind wings 

 all remarkably broad compared with their length, giving these particular 

 specimens quite a distinct facies. Strange to say, this abnormal con- 

 dition is sometimes more marked on one side than another. I have 

 specimens of Agrotis suffusa and A. valligera of a similar character. 

 Specimens with wings much narrower than the normal width are com- 

 mon in very many species. Another strange abnormity frequently 

 occurs in Viminia albovenosa, Leucania litoralis, and occasionally in 

 other species. Normally the wings in these species are well developed, 

 but appear always to have a slight tendency to a pointed apex. Fre- 

 quently, this peculiarity is developed quite abnormally, and the wings 

 become narrower and are drawn out in the same way as is normal in 

 Meliana flammea. Often too, this peculiarity is more developed on one 

 side than the other, and I have a specimen of Caradrina taraxaci 

 (Uanda) quite normal on one side, but exhibiting this same abnormity 

 in a very marked manner on the opposite side. I feel satisfied that 

 these, and similar variations in shape, if not, indeed all variations in 

 shape, are due to disease, or to injury to the larva at the exact period 

 of pupating. I remember seeing an abortive specimen of Orthosia 

 upsilon belonging to Mr. A. Robinson, of Brettanby Manor, Darlington, 

 and the abortion was so apparently due to disease, that I considered it 

 a kind of corroboration of my previously formed ideas on this subject. 



With regard to the markings, we come to an exceedingly wide 

 path in our subject, and it is very rare indeed, that some particular 

 species in a genus do not exhibit some characteristic variation in mark- 

 ings, although the genus as a whole, may not tend in that direction. 

 On the other hand, we find certain genera where almost every species 

 presents such a tendency to vary ; but it is strange, how, in very 

 closely allied species, one will vary indefinitely, while another will be 

 most constant. Apamea didyma and A. ophiogramma offer a striking 

 example, as also do A. gemina and A. unanimis in the same genus. In 

 the Cymatophoridce, there is a general tendency for variation to take 

 place in the size of the stigmata and also in the width between the 

 transverse lines near the centre of the wing. Perhaps this is better 

 exhibited in Asphalia flavicornis than any other species in the group. 

 Individual specimens also frequently show an asymmetrical character 

 both in die stigmata and markings, and I have noticed that asymmetry 

 is not at all an infrequent character in many genera. A strange pecu- 

 liarity in the old genus Acronycta the Viminia, Cuspidia and Bisulcia of 

 Chapman is the variation with regard to the position of the stigmata, 

 the normally separate stigmata being frequently united. This same 



