FLEAS 2Q5 



CONORHINUS MEGISTUS. This is called "Barbeiro" in Brazil on account of its 

 preference for biting the face. The Schizotrypanum cruzi undergoes a develop- 

 mental cycle in this bug which transmits the disease. 



SlPHONAPTERA. 



These are laterally flattened wingless insects and undergo a complete 

 metamorphosis. 



Pulicidae. 



This family is divided into two subfamilies the Pulicinae and the 

 Sarcopsyllinae. In the former the female remains practically unchanged 

 after fecundation, in the latter the abdomen becomes enormously dis- 

 tended with eggs, and the female remains stationary after her impreg- 

 nation in the burrow which she has made under the skin. 



Pulicinae. Formerly, with the exception of infection with Dipylidium caninum, 

 the fleas were only under suspicion as carriers of disease; ideas having been enter- 

 tained as to their being possible transmitters of relapsing fever, typhus fever and 

 kala azar. Trypanosoma lewisi is transmitted by fleas, either Pulex irritans or 

 C. canis. The trypanosome undergoes development in the flea and the infecting 

 material is in the faeces of the flea and transmission occurs by the licking on the part 

 of the rat of faeces from an infected flea. The infection has no connection with the 

 puncture wound of the flea as is the case with plague. As a result of the convincing 

 experiments of the British Plague Commission, their role in the transmission of 

 plague has been absolutely established. It is by the bite of the Xenopsylla cheopis 

 that plague is chiefly transmitted from rat to rat, and in bubonic and septicaemic 

 plague it is apparently the intermediary .in human infection. 



The average capacity of a flea's stomach is about 0.5 cmm. so that with a rat 

 dying with septicaemic plague and with possibly 100 million bacilli to one c.c. of 

 blood the flea would take in about 5000 bacilli. Furthermore these multiply in 

 the alimentary canal so that the digested blood teems with bacilli when reaching 

 the anus of the flea. The plague bacilli are passed out with the faeces and these 

 being rubbed into the puncture of the flea bite bring about infection. The puncturing 

 apparatus of the flea consists of a pointed epipharynx and two distally serrated 

 mandibles. These chitinous biting parts are contained in the labium which divides 

 distally into two labial palps. The maxillae are conspicuous triangular structures 

 and, projecting farthest anteriorly, are the conspicuous four-jointed maxillary palps, 

 often mistaken for antennae. By the apposition of the internally grooved mandibles 

 to the epipharynx a tube is formed through which the blood is sucked up. The 

 antennae are inconspicuous and are in close apposition to the sides of the head, 

 behind the eyes, and can only be well made out with a lens. Fleas have three pairs 

 of legs, and the male can be distinguished from the female by its smaller size and the 

 conspicuous coiled-up penis within the abdomen. The female has a conspicuous 

 gourd-like spermatheca which varies in shape in different species. The body of 



