72 NATURAL HISTORY OF SELBORNE 



not in other places fall in with a soil as much too loose 

 and mouldering, liable to flounder, and threatening to over- 

 whelm 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 (J>ulex irritans), swarming at the mouths of these 

 holes, like bees on the stools of their hives. 1 



The following circumstance should by no means be 

 omitted that these birds do not make use of their caverns 

 by way of hybernacula, 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 nidification, 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 libellula (dragon flies) almost as long as them- 

 selves. 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 en- 

 closures, they are dispossessed of their breeding-holes by 



1 See vol. i. p. 129. [R. B. S.j 



