Matrivorous habit of the species of Heterogynis. 181 



to determine whether there was any varietal distinction 

 between the two races, but this is very probable, as the 

 intermediate country and elevations were without any 

 " broom " capable of nourishing the species, so that the 

 two colonies were probably segregated with considerable 

 strictness. 



The extreme development of the matrivorous habit in 

 H. paradoxa, and its obviously great importance in the 

 economy of the species, afford an explanation of the 

 remarkably aberrant habits and structure of the female 

 imago, and give us some hints as to the probable steps by 

 which they were evolved. 



Though the latter are more or less hypothetical, and 

 therefore less certain than the former, we may take them 

 first, as they are so in point of time. 



We may safely assume that the first steps in the process 

 of evolution were similar to those that obviously obtained 

 in Psyche and Orgyia. Firstly, apterousness of the $ con- 

 sequent on laying the eggs, on or in the cocoon or close by. 

 Then eggs laid in the pupa-case. And somewhere at this 

 point the dominating conditions would probably be those 

 which I imagined still to obtain, as no doubt subsidiarily 

 they do, when I discussed this matter in connection with 

 H. penella (Ent. Trans., 1898, p. 46), viz. protection of the 

 eggs from enemies and from desiccation by the mother 

 dying in and blocking the open end of the pupa-case. At 

 this time the moth probably still retained some legs and 

 some scales or hairs. Both Psychids and Orgyias still 

 retain some hairs, so far as I know, in all cases. 



The delicate nature of the eggs (as in the allied 

 Anthroceras) would make protection against drought a 

 strong selective agency, and there would now come in the 

 matrivorous instincts of the larvee. These no doubt would 

 originate accidentally in the necessities of the larvse finding 

 a way of escape from the pupa-case, leading some of them 

 to do so by eating into, or at least nibbling the dead body 

 of the %. So soon as matrivoracity became definitely an 

 instinct then several forces would come into action. As 

 these would be the same that now keep the arrangements 

 in their present perfection we may better consider them in 

 connection with the explanation they afford of existing 

 facts. The very complete closure of the pupa-case, so that 

 it looks as if it had never been opened, and no moth ever 

 emerged from it, becomes very important when we regard 



