74 Proceedings of the Royal Physical Society. 



work in a group which has hitherto received far too little attention in 

 Scotland. It should be added that in what follows the references have 

 been reduced to a minimum, but a full Bibliography of papers, lists, and 

 records dealing with Scottish Siphonaptera will form part of a " Census " 

 now in preparation. 



I have arranged the observations made in the order of the chief stages of 

 the life-history. 



A. — Ovum and Oviposition. 



The act of egg-laying has not yet been observed by myself, but once or 

 twice eggs have been detected in dust or debris in the bottom of nests. 

 This powdery matter, composed largely of dried, rubbed-down faeces of the 

 birds mingled with scales from their young, forms a most suitable food for 

 the larvae of Geratophylli. It is much frequented by gravid females. Bird 

 flea eggs are relatively large, oblong, rounded at both ends, and opaquely 

 white. They are in my experience usually laid singly, and, unlike Mallo- 

 phagous eggs or Pediculine " nits," do not adhere to the surface on which 

 they are placed. Occasionally one or two eggs are found cohering, and 

 once a female (C. walkeri) in alcohol was accompanied by a regular chain 

 of eggs. These, however, may have been forced out of the abdomen by 

 contraction of the muscles in spirit. 



Geratophylli may also lay their eggs on the hosts themselves. From a 

 Meadow-Pipit (Anthus pralcnsis) I have taken a single egg, probably of 

 G. garei, as a female of this species occurred on the same host, and no 

 other parasite or indication of a parasite {e.g., eggs or empty skin) was 

 present. On an equally clean Redwing (Turdus iliacus), from Colinton, 

 December 1909, there was a single crushed egg attached to a feather by the 

 expressed yolk. This, too, apparently belonged to a Geratophyllus. 



B. — From Ovum to Imago. 



From 1905-1908 I had on several occasions bred Geratophylli by the 

 simple expedient of keeping nest linings in bags. The only care taken was 

 to avoid drying up of the larva? or pupae. In 1909 more accurate notes of 

 the time occupied in the various life stages were made, and in particular a 

 very interesting opportunity occurred of studying the whole life-history 

 under natural 'conditions. 



During the second week of March 1909, Mr Alex. Bennett, jun., Shank 

 Garden, Arniston, made a cavity in the decaying limb of an ash tree there, 

 in the hope of inducing Owls, observed to be haunting the spot, to nest. The 

 hole, some 2 feet in depth, was situated about 15 feet from the ground. 



