27 



fortieth of her previous bulk ; nevertheless the process of laying the 

 eggs is an elaborate one, requiring many and varied muscular move- 

 ments which could not be performed satisfactorily by the shrivelled 

 and empty moth ; both ends of each of its muscles would, in fact, be 

 close together, and no movement could take place. Most of these 

 species also have a very long ovipositor in order to reach the 

 bottom of the sac or pupa case and begin laying there. As the 

 laying is completed it becomes necessary to retract this long ovi- 

 positor, since the laying is now close to the mouth of the sac. If 

 the moth retains her bulk the ovipositor can be retracted, but not 

 without, since the rods of the ovipositor in many species reach right 

 up into the thorax. By means of inflation the original bulk is 

 maintained, the oviposition can be properly completed, and the final 

 disposition of the wool in the mouth of the sac can be satisfactorily 

 managed. 



In the higher Psychids the eggs are laid in the pupa case, which 

 the moth herself occupies at the same time, and one would suppose 

 that inflation would not be necessary. I have, however, never 

 watched the process, and know of no one that has, so that any 

 conclusions we may come to are pure hypothesis. What we do 

 know and see is that the moth leaves the case when egg-laying is 

 finished, and it is tolerably certain that the muscular action necessary 

 for extricating herself would be impossible in the collapsed con- 

 dition she presents when empty of eggs. The inflation is, then, 

 a necessary condition to this final journey ; whether of any use 

 during egg-laying we do not know, but we may imagine it does 

 not occur till this is completed. Heterogynis, who lays her eggs in 

 almost an identical manner, uses no inflation, nor does she leave 

 the pupa case, but dies above her eggs and forms a protective 

 closure to the pupa case containing them, affording also a first meal 

 to the young larvae when they hatch. I have recently come across 

 an instance of inflation in Coleoptera, in the case of (Drina {Chryso- 

 chlod) tristis, var. smaragdi/ia. The young larva, when about to 

 emerge from the egg, resorts to inflation; and I find it does so also 

 at its changes of moults. 



The mechanics involved in the bursting of the egg-shell and the 

 emergence of the young larva is of precisely the same nature as that 

 by which such Lepidoptera as E. lanestris and L. testudo break open 

 their cocoons. The young larva, when ready to hatch, completely 

 fills the egg-shell, which is a somewhat strong, tough structure, of a 

 short sausage shape, having its head at the top and its last segments at 

 the lower end of the egg. It secretes air into its alimentary canal, 

 and as the secretion goes on the tension of course gradually increases. 

 Assuming this to go on indefinitely, a point would be reached at 

 which the shell would burst irregularly, and probably explosively. 

 The larva, however, is provided with three blunt points on either 

 side, and their effect is to make the tension very acute along their 

 line before it reaches any severe strain generally, and the egg-shell 



