54 



The Arrangement of the Alimentary Canal and Mouth Parts 

 of the Bed Bug. 



The general scheme of the alimentary canal will be 

 sufficiently clear from the diagram (Fig. 20). There are two 

 pairs of salivary glands (s.g. and s.g. '), and the duct of the 

 larger or dorsal pair (s.g. J ) bifurcates shortly after it emerges 

 from the gland and both tubes run forward to the base of 

 the piercing organ. The exact way in which the three salivary 

 ducts on each side terminate has not yet been determined. 

 The mouth parts also differ from those of the flea in that 

 the sucking tube is made up by the apposition of four 

 elements instead of three. These are two maxillse (mx.) 

 and two mandibles (inn.). When not in use these delicate 

 piercing instruments are carried in a groove on the dorsal 

 aspect of the three-jointed labium (7.). Whilst feeding this 

 support is folded backwards under the head. 



Experiments on the Transmission of Relapsing Fever, Typhus, 

 and Plague ~by means of Bed Bugs. 



The observations of Tictin have already been referred to. 

 Although these show that the spirocheetas of relapsing fever 

 may live from some hours to many days, according to 

 circumstances, in the stomach of the insect, they give no 

 information as to whether the bed bug can in a natural way 

 transmit the disease. 



Christy (1902), M. Eabinowitch (1907), and Shellack 

 (1909) tried the experiment on themselves without success. 

 Their attempts were very thorough. Shellack, for instance, 

 fed 168 bugs, which had been previously nourished on a diet 

 of rat blood infected with Spirochceta recurrentis, upon 

 himself. The experiment lasted a month, and was so 

 arranged that a variety of intervals elapsed between the 

 ingestion of infected blood and the second meal. 



Breinl, Kinghorn and Todd (1906), Kabinowitch (1907), 

 and Sergent and Foley (1910) have also tried to transmit 

 relapsing fever to monkeys by means of bugs. Large numbers 

 of insects were employed by the former observers, sometimes 

 as many as 590 to one monkey. Their experiments were 

 carried on over two or three months. Bugs which had feel 

 upon an infected monkey at all stages of the disease were 

 used, and the interval between feeding upon the infected 

 and healthy animal varied. Nevertheless, no transmission 

 of the disease occurred. 



The only case of successful transmission was one experi- 

 ment by Nuttall (1907), who removed a bug shortly after it 

 had commenced to feed upon an infected mouse and allowed 

 it to complete its meal upon a normal mouse. 



Bed bugs were excluded from consideration as transmitters 



