IX ADVANCED THEORIES 119 



species, which makes war on crickets upon the 

 steppes in the neighbourhood of the Caspian Sea. 

 Thus in the lands bordering the Mediterranean we 

 have five different species whose larvae all live on 

 Orthoptera. 



Now let us cross the equator, and descend in 

 the other hemisphere to the Mauritius and Reunion 

 Islands, and we shall find, not a Sphex but a 

 Hymenopteron, nearly allied, of the same tribe, 

 Chlorion or Ampulex, chasing the horrid kakerlacs, 

 the curse of merchandise in ships and colonial 

 ports. These kakerlacs are none other than cock- 

 roaches, one species of which haunts our houses. 

 Who does not know this stinking insect, which, thanks 

 to its flat shape, like that of an enormous bug, 

 insinuates itself into gaps in furniture and parti- 

 tions, and swarms everywhere that there is food to 

 devour. Such is the cockroach of our houses — a 

 disgusting likeness of the not less disgusting prey 

 beloved by the Chlorion. Why does a near relation 

 of our Sphex select the kakerlac as prey. The 

 reason is simple : With its buglike form the 

 kakerlac is an Orthopteron by the same rights as 

 the grasshopper, ephippiger, and cricket. From 

 these six examples, the only ones known to me, 

 and from such widely distant localities, may we 

 not conclude that all Sphegidae hunt Orthoptera ? 

 Without adopting so sweeping a conclusion, one at 

 least sees what the usual food of their larvae must be. 



There is a reason for this surprising choice. 

 What is it ? What motives fix a diet which in 

 the strict limits of one and the same entomological 

 order is now composed of ill-smelling kakerlacs, now 



