xxviii President's Address. [Aug. 28, 



corum ; but this Osmid chooses generally as a residence a hollow twig, 

 which it partitions with clay. T could hardly have suspected the 

 Anthrax, when alighting on a ledge of the wall, to have also chosen 

 the Odynerus larva for its progeny. Yet, there is no longer any 

 doubt of it now. 



There is the nymphal case projecting from one of the galleries, 

 which, when explored, yields debris, which tell their own tale. But 

 how- could such a feeble insect as an Anthrax choose to deposit her 

 egg on that cemented surface, so hard that it is with difficulty that I 

 can make a breach in it. She is not provided with terminal auger ; 

 she has no mandibles, only an haustellum, her feet are unprovided 

 with bristles or fossorial implements of any kind. 



Thanks to the patience and keen power of observation of Fabre, we 

 have now the key to that mystery, and larval dimorphism is now 

 known to bridge the distance to hypermetamorphosis. 



Upon the rugged surface of the wall the Anthrax has deposited her 

 egg ; that is all. 



From that egg will issue the singular creature you will perceive in 

 this diagram. It is only one millimetre in length. What its mother 

 has not been able to do for it it must do for itself ; it must fight its 

 way through small chinks invisible to my eye. The mother has not 

 chosen this place for it without good cause, and instinct warns it that 

 there, at a greater or lesser distance, lies a fat grub or grubs. It has 

 reached it at last, not without hard work ; it may now consider the 

 tempting morsel as its own, but it has still to pierce the silky cocoon 

 wherein the Odynerus larva is about to undergo its metamorphosis. 



When this is over the first change begins — larva No. 1 becomes 

 larva No. 2, and she is now having her first meal. 



We see now a legless worm which sucks its victim dry without 

 perforating the skin. When this is over, there comes the third 

 metamorphosis — i.e., the nymph. Now among all insects undergoing 

 such a process there is always a cessation of movement during the 

 nymphal stage ; life is apparently suspended, and, except for a few 

 twitchings, the chrysalis is practically motionless. Not so with the 

 Anthrax, however. The only easy time it has had has been in the 

 secondary stage. In the primary one it has had to fight its way into 

 the cell of its host. In the nymphal state it must manage to open for 

 itself a way out of the cell, because the feeble fly, the full-grown 

 insect, will never be able to perforate the walls. And this is why the 

 head of the nymph is armed with pick and shovel, her segments with 

 spines and bristles which she will use as a lever, and wheu the half of 

 the body is out of the cell, when it is firmly anchored by the stiff 

 ciliae and the terminal segment, the thorax will split in a crucial form 

 and through that rent the Anthrax emerges into the light of day. 



