OF SELBORNE. 177 
thefe beginnings ivere intentionally made in order to be in the 
greater forwardnefs for next fpring, is allowing perhaps too much 
forefight and rerum prudent'm to a fimple bird. May not the caufc 
of thefe latehra being left unfiniihed arife from their meeting 
in thofe places with ftrata too harfti, hard, and folid, for their 
purpofe, which they relinquifli, and go to a frcfh fpot that works 
more freely ? Or may they not in other places fall in with a foil 
as much too loofe and mouldering, liable to flounder, and threaten- 
ing to overwhelm them and their labours ? 
One thing is remarkable- that, after fome years, the old holes arc 
forfaken and new ones bored; perhaps becaufe the old habitations 
grow foul and fetid from long ufe, or becaufe they may fo abound 
with fleas as to become untenantable. This fpecies of fwallow 
moreover is ftrangely annoyed with fleas : and we have feen fleas, 
bed-fleas {;pulex irritans), fwarming at the mouths of thefe holes, 
like bees on the ftools of their hives. 
The following circumfl:ance fliould by no means be omitted — 
that thefe birds do not make ufe of their caverns by way of hyber- 
nacula, as might be expefted ; iince banks fo perforated have 
been dug out with care in the winter, when nothing was found 
but empty nefts. 
The fand-martin arrives much about the fame time with the 
fwallow, and lays, as flie does, from four to fix white eggs. But 
as this fpecies is cryptogame, carrying on the bufmcfs of nidification, 
incubation, and the fupport of it's young in the dark, it would 
not be fo eafy to afcertaln the time of breeding, were it not for the 
coming forth of the broods, which appear much about the time,, 
or rather fomewhat earlier than thofe of the fwallow. The ncftlings 
are fupported in common like thofe of their congeners, witli gnaCf, 
and other fmall infeds ; and fometimer, rhey are fe<l with Ut'cUi'Lc 
A a (dragon- 
