OF SELBORNE. 271 



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, car- 

 rying 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 com- 

 mon like those of their congeners, with gnats and other 

 small insects ; and sometimes they are fed with Libel- 

 lulce (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 swal- 

 lows and house martins do, we have never yet been 

 able to determine : nor do we know whether they pur- 

 sue and attack birds of prey. 



When they happen to breed near hedges and enclo- 

 sures, they are dispossessed of their breeding holes by 



des Sciences Naturelles. It may aid those who may be disposed to search 

 for so minute an organ on so small a creature to be informed that, accord- 

 ing to M. Duges, there is behind each eye a shallow but broad cavity, 

 ending below in a cleft and covered by a kind of operculum which is tri- 

 angular and immoveable : an arrangement which he compares to the orbit, 

 the temporal fossa, and the zygoma of the human skull. Under the oper- 

 culum and within the cleft is hidden a small flat body, which is raised, at 

 times, briskly into the uncovered portion of the depression. This is the 

 antenna, of larger size than is well adapted to the small space in which 

 it is lodged, and rendered capable of being contained in so limited a ca- 

 vity only by the flexures of its joints. The number or the form of these 

 joints appears to differ in almost every one of the indigenous fleas, nearly 

 twenty of which have now been discovered infesting various quadrupeds 

 and birds ; each of them being generally appropriated to its peculiar 

 species. 



The sand martin's flea remains in considerable numbers in the deserted 

 nests after the departure of the bird. E. T. B. 



