FLEAS 113 



C. rossittensis in much smaller numbers, the latter can easily be over- 

 looked. 



The host has split into two well marked geographical races. It is 

 claimed that C. rossittensis can also be divided into two subspecies — one 

 off the carrion-crow and one off the hooded crow, but the evidence is 

 meagre and the suggestion must be regarded as tentative. Unfortunate- 

 ly, no fleas have been found in the nest of the hooded crow in Great 

 Britain. 



The eighth sternites of the males and the shape of the receptaculum 

 seminis of" the females show features by which C. rossittensis and C. 

 gallinae can be separated. 



THE MOORHEN FLEA, Dasypsyllus gdUnulae, (Plate XIII, and Map 4). 

 This strange flea which originally hailed from the South American 

 continent has an isolated position among British bird fleas. It is the 

 commonest species we have apart from C gallinae and one of the largest. 

 It is also particularly easy to identify, both sexes being quite unlike any 

 other of our bird fleas. The two heavy spines, like the horns of an 

 antelope, on one of the genital flaps of the male can be spotted with a 

 hand lens, and the deep "bite" out of the seventh sternite of the female 

 is equally unmistakable. 



D. gallinulae is very frequently found in nests with other bird fleas 

 such as C. gallinae and C. garei, and a closer study of its ecolog)^ would 

 no doubt prove extremely interesting. It is found relatively more often 

 on the body of the host compared with hen flea and duck flea, which 

 are essentially nest dwellers. In Great Britain it has been found 

 parasitising 59 different species of bird hosts. These are varied, ranging 

 from the moorhen, woodcock and grouse, to the robin, goldcrest, 

 willow-tit, and tree-creeper, although generally speaking (seep. loi) 

 it prefers nests in low positions. 



D, gallinulae varies considerably in size and a series of both small 

 and large specimens will hatch out of the same nest. 



THE SAND-MARTIN FLEA, C. styx (Platcs XIV, XVI). This flea 

 has the distinction of having been mentioned by Linnaeus, but though 

 recording it in numbers in the nests of sand-martins he mistook it for 

 the human flea. 



