LICE. 287 



louse of the ox : * the louse of the eagle f is not 

 larger than the louse of the rook ; J while the louse 

 of the great snowy owl scarcely exceeds that of 

 the tiny gold-crested wren.|| Birds also of the same 

 size harbour species that are very dissimilar in this 

 respect. The louse of the sparrow-hawk ^f does not 

 measure more than three-quarters of a line in length ; 

 while that of the hobby** (of which I have two 

 specimens taken by myself from that bird) is among 

 the most gigantic of its race, and exceeds a quarter 

 of an inch. 



Some species of birds are much more troubled 

 with these parasites than others. The rook and the 

 common buzzard appear to be particularly infested 

 by them. The latter I have often found swarming 

 with them, more especially the feathers about the 

 head and neck, to an extraordinary degree. Other 

 birds, again, appear to be nearly free from lice alto- 

 gether. The common heron is one, on which I 

 never could detect a single specimen, though repeat- 

 edly searched for this purpose. j-j" It once occurred 

 to me, that the dust, which naturally abounds so in 

 the plumage of this bird, might have the effect of 



* H. eurysternus, Id. pi. xxv. f. 5. 



t Docophorus aquilinus, Id. pi. ii. f. 7. 



J D. atratus, Id. pi. iv. f. 8. 



D. ceblebrachys, Id. pi. i. f. 3. 



|| D. reguli, Id. pi. vi. f. 4. 



IF D. nisi, Id.pl. iii. f. 11. 



** Lamobothrium laticolle, Id. pi. xxiii. f. 4. 



ft Mr. Denny, however, has described two species found on the 

 heron, Lipeurus leucopygw (pi. xiv. f. 4.) and Colpocephalum im- 

 portunum (pi. xviii. f, 1.), though the former would seem rare. 



