MASON-BEES. 23 



their egg into the nest of another species. These flies are 

 continually prowling about and prying into every corner, 

 to find, by stealth, a nidus for their eggs. It might have 

 been some such consideration as this which induced the 

 wasp to carry off the fragments as they were successively 

 detached. That concealment was the motive, indeed, was 

 proved; for one of the fragments which fell out of the hole 

 by accident, she immediately sought for at the bottom of 

 the wall, and carried off like the rest. It was no eas}^ 



Mandibles— Jaws of Mason- Wasp.— Greatly nuignified. 



matter to get out one of the fragments, as may readily be 

 conceived when the size of the insect is compared with that 

 of the entrance, of which this ( J|) is the exact size, as taken 

 from the impression of a bit of dough upon the hole when 

 fi.nished. It was only by seizing the fragment with her 

 jaws, and retreating backwards, that the matter could be 

 accomplished ; though, after the interior of the excavation 

 was barely large enough to admit of her turning round, she 

 more than once attempted to make her exit head-foremost, 

 b)ut always unsuccessfully. The weight of the fragments 

 removed did not appear to impede her flight, and she 

 generally returned to her task in about two or three 

 minutes. 



Within two days the excavation was completed ; but it 

 required two other days to line it with a coating of clay, to 

 deposit the eggs, two in number, and, no doubt, to imprison 

 a few live spiders or caterpillars, for the young when 

 hatched — a process which was first observed by Ray and 

 Willughby,* but which has since been frequently ascer- 



* Rav, Hist. Insect., 254. 



