CARPENTERS AND WOOD- WORKERS 105 



tough brownish cocoons. The perfect insects are 

 black and yellow (some all black), often banded in 

 a very wasp-like fashion, and they have broad, 

 square-cut heads. The usual food stored for their 

 grubs consists of two- winged flies (Diptera), and in 

 some cases each species of Crabro has a particular 

 species of fly it uses for this purpose ; but there 

 are several remarkable departures from the rule. 

 Three of our native species {Crabro tibialis, C. 

 clavipes, and C. capitosus) use bramble-stems for 

 their burrowing operations. C. signatus and C. 

 dimidiatus bore into posts and stumps, the latter 

 species storing up blue-bottle flies. C. leucostomus 

 has a preference for the soft wood of decaying 

 willow-trees, and as grub-food selects the bright- 

 green fly Chrysomyia polita. C. quadrimaculatus, 

 C. chrysostomus, and C. interruptus also burrow into 

 dead wood. 



The Peckhams found C. sexmaculatus burrowing 

 into the sound wood of an above-ground root of 

 the lime-tree. Five of them were sinking their 

 shafts side by side — 



" . . . sawing and cutting in the most humdrum 

 and practical manner. One of them, presumably the 

 earliest riser, was well down in the root, and came 

 backing up once in a while, pushing a lot of wood- 

 dust out of the hole. This was spread out by 

 means of legs and mandibles, and was then blown 

 away by the fa r> ring wings of the little worker, 

 who circled about just above the ground until the 

 last grain had disappeared. . . . After this series of 



