Matrivorous habit of the species of Heterogynis. 183 



so obvious, comparing the few pellets remaining from 

 Heterogynis, with the deposits usual in most moths of 

 similar size, that the matter is self-evident. The urates 

 represent the amount of tissue waste that has taken place. 

 Now in Heterogynis this tissue waste is that involved in 

 the muscular exertion of spinning the cocoon, in casting 

 the larva skin, and in the emergence and retreat of the 

 moth, and in laying her eggs. The whole process of 

 histolysis and development by which the larval structures 

 are absorbed, and the imaginal (wings, legs, hairs, scales, 

 antennae, etc.) are built up from their embryonal condition 

 is completely saved ; this process must in ordinary Lepido- 

 ptera require a good deal of expenditure of tissue material. 

 In Heterogynis not only are no imaginal structures de- 

 veloped, but the larval skin muscles and the larval 

 colouring remain unchanged. I have already noted the 

 skin to be devoid of the usual skin points, but there are in 

 fact no hard parts whatever, no head plate, no prothoracic 

 plate, no appendages, no solid parts to the ovipositor, etc. 

 Everything is eatable, and all is eaten ; I do not think we 

 can find in the imaginal composition any explanation of 

 why the larvae void no excreta during a whole instar, and 

 until, during the second instar, they have made their 

 escape from the parental cocoon. 



This is probably a matter of hygiene, b}' which the 

 presence of such excreta would be most undesirable 

 amongst the crowded larvae, especially if their emergence 

 were delayed by any climatic or other causes. The case of 

 such larvae as those of Cnetliocampa, whose nests are loaded 

 with frass, are hardly parallel, since these nests are very 

 roomy, and the portion into which the larvae crowd are 

 more or less free from frass, whilst in the Heterogynis 

 pupa-case the larvae are solidly wedged together with no 

 spare space and very few threads of silk. That there shall 

 be no frass, however, that the larvae shall not require to 

 void anything, it is no doubt necessary that the pabulum 

 shall be of a most concentrated and digestible nature. 



Summarizing the facts now advanced, there is first the 

 correction of the error as to first stage of H. paradoxa, 

 due to the recognition of the circumstance that it does 

 not emerge from the maternal pupa-case and cocoon till it 

 has moulted into the second instar. Secondly, the import- 

 ance in the economy of the genus, and especially in 

 H. paradoxa, of the matrivorous habit, all the details 



