1 84 NATURAL HISTORY OF SELBORNE. 



the greater forwardness for next spring is allowing perhaps too 

 much foresight and rerum prudentia to a simple bird. May not 

 the cause of these latebrce. being left unfinished arise from their 

 meeting in those places with strata too harsh, hard, and solid, for 

 their purpose, which they relinquish, and go to a fresh spot that 

 works more freely ? Or may they not in other places fall in with 

 a soil as much too loose and mouldering, liable to flounder, and 

 threatening to overwhelm them and their labours? 



One thing is remarkable that, after some years, the old holes 

 are forsaken and new ones bored ; perhaps because the old 

 habitations grow foul and fetid from long use, or because they 

 may so abound with fleas as to become untenantable. This 

 species of swallow moreover is strangely annoyed with fleas ; and 

 we have seen fleas, bed-fleas (pulex irritans), swarming at the 

 mouths of these holes, like bees on the stools of their hives. 3 



The following circumstance should by no means be omitted 

 that these birds do not make use of their caverns by way of hyber- 

 nacula, as might be expected ; since banks so perforated have 

 been dug out with care in the winter, when nothing was found 

 but empty nests. 



The sand-martin arrives much about the same time with the 

 swallow, and lays, as she does, from four to six white eggs. But 

 as this species is cryptogame, carrying on the business of nidifica- 

 tion, incubation, and the support of its young in the dark, it would 

 not be so easy to ascertain the time of breeding, were it not for the 

 coming forth of the broods, which appear much about the time, or 

 rather somewhat earlier than those of the swallow. The nestlings 

 are supported in common like those of their 'congeners, with gnats 

 and other small insects ; and sometimes they are fed with libelktltz 

 (dragon-flies) almost as long as themselves. In the last week in 

 June we have seen a row of these sitting on a rail near a great 

 pool as perchers, and so young and helpless, as easily to be taken 

 by hand ; but whether the dams ever feed them on the wing, as 

 swallows and house-martins do, we have never yet been able to 

 determine ; nor do we know whether they pursue and attack birds 

 of prey. 



When they happen to breed near hedges and enclosures, they 



