258 THE entomologist's record. 



ornitopus, X. soda, Crocallis elinijuaria, one is immediately confronted 

 with the remarkable fact that, although mostly belonging to widely 

 separate genera, they have one thing in common, they are all more or 

 less addicted to oak, and are all about full-groAvn at the same time^ 

 Further their period of growth coincides Avith, or closely follows, that 

 of many other oak-feeders, such as Hyhernia defoliaria, H. aurantiaria, 

 H. leucophaearia, Hvnera pennaria, Phiijalia pedaria, Biston hispidaria, 

 Boarmia roboraria and B. consortaria, Clieimatohia hrumata and C. 

 boreata, Tortrix viridana, and many Noctuids such as Taeniocampa 

 incerta, T. stabilis, T. pidvendenta, Dichonia aprilina, Catoccda sponsa 

 and C. proviiiisa, and, consequently it frequently happens, particularly 

 as many of the above-mentioned species are outrageously common and 

 destructive, that the oaks are almost, or entirely, denuded of foliage. 

 I have, on several occasions, seen extensive oak forests entirely stripped 

 of every vestige of foliage at the end of May and early June, the 

 principal offenders being the species of Hyheryiia and Cheimatobia 

 brumata and C. boreata. On one occasion, several years ago, the oak- 

 woods near Northaw, Herts, at the end of May looked as they might 

 in December, so thoroughly had Hybernia defoliaria and Pldgalia 

 pedaria done their work, and the following year they were in nearly 

 the same state. This year again several oak-woods by Berlin were 

 stripped by the larvae of Tortrix viridana and Hybernia defoliaria 

 amongst others. 



Now it seems to me that the constant recurrence of this state of 

 things would gradually force other species of larvae feeding on oak to 

 seek some other form of nutriment, and it is evident that the nearest 

 and best substitute for the original food, oak, would be the despoilers. 

 No doubt at first the habit was only adopted in case of necessity, and 

 in many cannibals this is still the case, and out-and-out cannibals 

 were only very gradually evolved, until such species as T. yracilis 

 and Cosmia trapezina became cannibals by choice. Mr. Bacot tells me 

 that C. trapezina, when forced to subsist on a vegetable diet, is said to 

 emerge undersized, and anyone who has tried to rear a brood of T. 

 gracilis will know that, in spite of abundant food, only one specimen,, 

 usually a large female, will be bred. 



Another very bad cannibal, Senta maritima, is also more or less a 

 victim of circumstances. The larva passes the winter in the dry stems 

 of reeds, for choice in the old galleries of Nonagria geininipiincta, but 

 it does not hybernate in the true sense of the word as, although it is 

 sometimes found stiff and frozen during a very hard frost, it is usually 

 active. The reed-stems are the favourite hiding-places of all sorts of 

 insects and spiders, and they are mostly in a semidormant state, and 

 these form the prey of this larva. This species is best bred in cap- 

 tivity on a diet of scraped beef. Considering the habitat of this larva,, 

 it is difficult to know what else it could eat, as the dried stems of the 

 reeds can scarcely be a satisfactory pabulum, and there is nothing else 

 to be got. 



It seems to me, therefore, that the habit of cannibalism has never 

 in the first instance been acquired by choice, but always as a case of 

 necessity. 



