IX ADVANCED THEORIES 125 



portion of a corpse that would infect the cell and be 

 useless to the larva, not yet to be hatched for several 

 days. It is perfectly clear that Darwin's insect was 

 not a Sphex, strictly speaking. What, then, did he 

 see ? The word fly, by which the captured prey is 

 designated, is a very vague term which might be 

 applied to the greater part of the immense order of 

 Diptera, and therefore leaves us uncertain among 

 thousands of species. Probably the name of Sphex 

 is used equally vaguely. When Darwin's book 

 appeared, not only the real Sphegidae were so called, 

 but also the Crabronides. Now among these last 

 some provide their larvae with Diptera, the prey 

 required for the unknown Hymenopteron of the 

 English naturalist. Was then Darwin's Sphex a 

 Crabro ? No, for these hunters of Diptera, like the 

 hunters of any other game, require prey which will 

 keep fresh and motionless, but half alive for the 

 fortnight or three weeks needed before the eggs 

 hatch, and for the complete development of the 

 larvae. These little ogres require meat not decayed, 

 nor even high, but fresh. I know no exception to 

 this rule, and therefore the name Sphex cannot have 

 been used in its old meaning. 



Instead of dealing with a precise fact, really worthy 

 of science, we have an enigma to find out. Let us 

 continue to examine it. Several of the Crabronides 

 are so like wasps in figure and form and shape and 

 their yellow and black livery, that they might deceive 

 any eye unpractised in the delicate distinctions of 

 entomology. In the eyes of every one who has not 

 made a special study of the subject, a Crabro is a 

 wasp. Is it not possible that the English observer. 



