CHRYSIDIDJE. 191 



the Chrysis family approaches the Ichneumons. They best 

 merit the name of "Cuckoo-flies," as they fly and run briskly 

 in hot sunshine, on posts and trees, darting their ovipositor into 

 holes in search of the nests of other Hymenoptera, in which to 

 lay their eggs. Their larvae are the first to hateh and devour 

 the food stored up by other fossorial bees and wasps. "St. 

 F:i r^oau, however, who has more carefully examined the econ- 

 omy of these insects, states that the eggs of the Chrysis does 

 not hatch until the legitimate inhabitant has attained the greater 

 part of its growth as a larva, when the larva of the Chrysis 

 fastens on its back, sucks it, and in a very short time attains 

 its full size, destroying its victim. It does not form a cocoon, 

 but remains a long time in the pupa state." (Westwood.) 



" In the Entomological Magazine has been noticed the dis- 

 covery of Hedychrum bidentulum, which appears to be parasitic 

 upon Psen caliginosus ; the latter insect had formed its cells in 

 the straws of a thatched arbor, as many as ten or twelve cells 

 being placed in some of the straws. Some of the straws, per- 

 haps about one in ten, contained one or rarely two, of the 

 Hedychrum, placed indiscriminately amongst the others. 

 "VValkenaer, in his Memoirs upon Halictus, informs us that 

 Hed3 r chrum lucidulum waits at the mouth of the burrows of 

 these bees, in order to deposit its eggs therein ; and that when 

 its design is perceived by the bees, they congregate together 

 and drive it away. St. Fargeau states that the females of 

 Hedychrum sometimes deposit their eggs in galls, while II. 

 regium oviposits in the nest of Megachile muraria ; and he 

 mentions an instance in which the bee, returning to its nearly 

 finished cell, laden with pollen paste, found the Hedychrum 

 in its nest, which it attacked with its jaws ; the parasite im- 

 mediately, however, rolled itself into a ball, so that the Mega- 

 chile was unable to hurt it ; it, however, bit off its four wings 

 which were exposed, rolled it to the ground and then deposited 

 its load in the cell, and flew away, whereupon the Hedychrum, 

 now being wingless, had the persevering instinct to crawl up 

 the wall to the nest, and there quietly deposit its egg, which it 

 placed between the pollen paste and the wall of the cell, which 

 prevented the Megachile from seeing it." (Westwood.) 



In Cleptes the -underside of the abdomen is not hollowed out ; 



