136 THE NATURAL HISTORY 



side-fly, from its running sideways like a crab. It creeps 

 under the tails, and about the groins of horses, which, at 

 their first coming out of the north, are rendered half 

 frantic by the tickling sensation ; while our own breed 

 little regards them. 



The curious Reaumur discovered the large eggs, or 

 rather pupae, of these flies as big as the flies themselves, 

 which he hatched in his own bosom. Any person that 

 will take the trouble to examine the old nests of either 

 species of swallows may find in them the black shining 

 cases of the pupae of these insects : but for other par- 

 ticulars, too long for this place, we refer the reader to 

 VHistoire d'Insectes of that admirable entomologist. Tom. 

 iv. pi. II. 



LETTER XVI 



TO THE HONOURABLE DAINES HARRINGTON 



Selborne, Nov. 23, 1773. 

 Dear Sir, 



In obedience to your injunctions I sit down to give you 

 some account of the house-martin, or martlet ; and, if my 

 monography of this little domestic and familiar bird should 

 happen to meet with your approbation, I may probably 

 soon extend my inquiries to the rest of the British hirun- 

 dines — the swallow, the swift, and the bank-martin. 



A few house-martins begin to appear about the six- 

 teenth of April ; usually some few days later than the 

 swallow. For some time after they appear the hirundines 

 in general pay no attention to the business of nidification, 

 but play and sport about either to recruit from the fatigue 

 of their journey, if they do migrate at all, or else that 

 their blood may recover its true tone and texture after it 

 has been so long benumbed by the severities of winter. 

 About the middle of May, if the weather be fine, the 

 martin begins to think in earnest of providing a mansion 



