592 AN]SrUAL BEPOET SMITHSONIAN INSTITUTION, 1916. 



other eggs, and as soon as this is accomplished there emerges a vermi- 

 form larva which "sits at the table" and sucks in its victim by 

 mouthfuls. In another parasite of the Chalicodoma, Monodon- 

 tomerus, this polymorphism is useless, for the larvae are very small 

 and a great number can be tabled around the nymph that serves for 

 their nourishment. On the other hand, polymorphism is necessary 

 among the Diptera of the genus Anthrax, which is likewise parasitic 

 of the nesting bees. But here the primary larvae are not extermina- 

 tors: hatched outside of the cell where the Anthrax eggs are laid, 

 their role is to soften the walls of mortar, so as to slip througli the 

 fissures, which readily yield to their tenuous bodies and the long 

 terminal hairs. 



The researches of Fabre on the Coleoptera of cow-dung show us 

 habits still more diverse and perhaps more interesting. Each species 

 has its special habitat and Fabre studied them in gi'eat numbers: 

 the sacred beetle (Ateuchus), Onthophagus, Copris, Onitis, etc. 

 Observation is here particularly difficult for these insects lay their 

 tsggs underground and it is at the bottom of obscure galleries that 

 their larvae are found ; but the ingenious biologist knew well how to 

 overcome other obstacles. 



In this extensive series of works there may be chosen as an ex- 

 ample the history of the sacred beetle, Ateuchus sacer^ of which 

 Fabre wrote the first chapter in the middle of the last century and 

 the final chapter 50 years later. Since ancient times it has been 

 known that this singular insect made little balls of dung and rolled 

 them into a burrow where it buried itself with them; and it was 

 acknowledged that this ball served to nourish the adult as well as its 

 offspring. But that is nothing; though the pill is suitable for the 

 parents, it is too coarse for the delicate intestine of the larvae. For 

 these last there must be a special dung, fine and well sorted, which 

 the mother kneads into a fine pear-shaped core that will serve for a 

 home and a covering for the future larva. Its wall is hard and the 

 center soft, and the egg^ resembling a great pearl of amber, is at- 

 tached to the tip of the pear, lodged in a porous cell where the air 

 can easily enter. Here the young larva is hatched. It gets its nour- 

 ishment from the unctuous matter, and in the hard shell it will trans- 

 form into the chrysalis, then into the adult. The wonderful chapters 

 given to this history must be read to understand the difficulties that 

 the biologist had to overcome and the rooted errors that he made 

 to disappear. Among these last errors I will single out that which 

 described these insects as helpful beings always ready to offer a 

 strong hand to an embarrassed confrere. When a sacred beetle with 

 great effort rolls its round pill, another one very often comes to its 

 rescue; this was done, however, not in the least to render aid, but 



