OF SELBORNE. 185 



sheltered districts, over some lake, or under some hanging 

 wood, or in some hollow vale, especially in windy weather. 

 They breed the latest of all the swallow kind: in 1772 

 they had nestlings on to October the 21st, and are never 

 without unfledged young as late as Michaelmas. 



As the summer declines, the congregating flocks increase 

 in numbers daily, by the constant accession of the second 

 broods ; till at last they swarm in myriads upon myriads 

 round the villages on the Thames, darkening the face of the 

 sky as they frequent the aits of that river where they 

 roost. They retire (the bulk of them I mean) in vast flocks 

 together, about the beginning of October : but have ap- 

 peared of late years in a considerable flight in this neigh- 

 bourhood, for one day or two, as late as November the 3rd 

 and 6th, after they were supposed to have been gone for 

 more than a fortnight. They therefore withdraw with us 

 the latest of any species. Unless these birds are very 

 short-lived indeed, or unless they do not return to the 

 district where they are bred, they must undergo vast 

 devastations somehow, and somewhere ; for the birds that 

 return yearly bear no manner of proportion to the birds that 

 retire. 



; House martins are distinguished from their congeners 

 by having their legs covered with soft downy feathers down 

 to their toes. They are no songsters ; but twitter in a pretty 

 inward soft manner in their nests. During the time of 

 breeding, they are often greatly molested with fleas. 1 



1 Allusion has been already made to the parasites of swallows in the 

 previous letter, p. 180, and some further remarks on the subject will be 

 found later on in Letters XX. and XXI. Should the reader be curious 

 to learn something more of these singular insects, reference may be made 

 with advantage to Denny's " Monographia Anoplnrorum Britannia," an 

 essay on the British species of parasitic insects. ED. 



