INDIAN BLOOD-SUCKING INSECTS. 
659 
thus infect them with the plague bacillus which the fleas have previously 
sucked up with the blood of the rats on which they last fed. The litera¬ 
ture on the subject of fleas and plague is considerable, and the student 
is referred to the Reports on Plague Investigations in India issued by the 
Advisory Committee, and published in the “ Journal of Hygiene,” Vols. 
VI and VII. The classification of the group is somewhat difficult, as it is 
based largely on minute characters. C. F. Baker’s “ North American 
Siphonaptera ” and Jordan and Rothschild’s “ Revision of the Non- 
Comb-eyed Siphonaptera ” (Parasitology, Vol. I) may be consulted. 
The ‘ ‘ Comb ’ ’ refers to a row of stout spines round the lower part of 
the head which is present in certain species, as inP. felis , the cat and 
dog flea. This species is shown on PL LXXI, copied from the Plague 
Investigation Report, on which are also shown Cteno'psylla musculi, a 
mouse and rat-flea ; Pulex irritans, the human flea; Ceratopsyllus 
fasciatus , the European rat-flea ; and Sarcopsylla gallinacea, the fowl-flea. 
INDIAN BLOOD SUCKING INSECTS. 
As we all know, India is a country which has its full share 
of those vermin which spend the whole or part of their lives 
on the bodies of men and other warm-blooded animals, and also 
of those equally annoying insects which alight upon the body 
of their victim only when intent on gorging themselves with his 
blood. Of common vermin, the Bird-lice or Mallophaga (p. 110), are not 
blood-suckers, though they live as parasites on the bodies of their hosts : 
the blood-sucking species of insects at present known in India may be 
said to belong exclusively to two Orders, Diptera and Rhynchota. To 
the first of these may be assigned the Fleas, which probably represent a 
much-specialised offshoot from the old Dipterous stock, though they are 
generally given the rank of a separate Order or Sub-order (Siphonaptera). 
They represent that section of the Diptera which pass a considerable 
portion of their adult life on the host, though the egg, larval, and pupal 
stages are usually gone through elsewhere, in dusty and dirty places. 
Their importance in connexion with plague is well known. Except for 
the fleas, few blood-sucking Diptera spend much time on the body of the 
host, but the lives of adult Nycteribiidce and Hippoboscidce afford an 
interesting series of examples of variat’on in this respect. Some of 
them, for instance the one figured on PL LXIX, fig. 8, appear to pass at 
least most of their lives on the host, and most of these species are 
wingless or feeble-winged : at the other end of the scale are the common 
cattle-flies ( Hippohosca ) which have strong wings, are quick fliers, and 
are always ready to strike camp and leave the host on whom they have 
