470 SANITARY ENTOMOLOGY 



carcass to another, thus enabling the flies and other insects which visit 

 food to further distribute the germs. Proust found quantities of living 

 Dermestes vvlpinus Fabricius in goat skins taken from anthracic ani- 

 mals. He found virulent anthrax bacillus in their excrement and also 

 in their eggs and in the larvae. Heim also had occasion to examine some 

 skins which were suspected of having caused anthrax in persons engaged 

 in handling leather. He found the larvae of Attagenvws pellio Linnaeus, 

 Anthrenus museorum Linnaeus, and Ptinus also fully developed insects 

 of the latter species on the skins. All these insects had virulent anthrax 

 bacillus (spores) on their bodies and in their excreta. 



The greater proportion of the cases of beetle transmission of disease 

 are those in which the beetle serves as an intermediate host of a parasitic 

 worm. In most of these cases the beetle larvae are found in excreta. They 

 ingest the eggs of the worms and the transformation takes place within 

 their bodies. The worms are then eaten by animals and the infection is 

 carried on. Since Doctor Ransom, in his lecture, has summarized all of 

 the evidence, it is unnecessary to repeat at this time. 



We are not apt to associate the transmission of plant diseases by 

 insects but the cases are strongly analogous. Just recently F. B. Rand 

 has demonstrated the transmission of cucurbit wilt, which is caused by 

 Bacillus tracheiphilus, by means of the cucumber beetle, Diabrotica vit- 

 tata Fabr. He has found that the beetles take up the bacillus in eating 

 an injured leaf and has been able to demonstrate the presence of the 

 bacillus in the body of the insect by dissection and culture with subse- 

 quent inoculation. He has conclusively proven that the disease can be 

 transmitted only by means of this and closely related beetles. He has 

 found also that the normal bacillus content of the abdomen may, in a 

 large proportion of cases, destroy the wilt bacillus. It is quite probable 

 that infection in this case is similar to that caused by the house fly, in 

 that the infected excreta come in contact with the recently eaten surfaces 

 of the leaf as the beetle moves forward. 



It has been found that beetles can transmit mosaic disease of tobacco. 

 It is not at all out of the way to expect that we will find ultimately a 

 similar transmission in this case and in many other plant diseases. 



LIST OF REFERENCES 



Castellani, A., and Chalmers, A. J., 1913. — Manual of Tropical Medi- 

 cine. 



Cornelius, H. B., 1919.— Indian Med. Gaz., vol. 54, No. 2, pp. 72, 73. 



Cornwall, J. W., 1916. — Indian Joum. Med. Research, vol. 3, pp. 52- 

 57, and 540-557. 



EUingham, E. H., 1914.— Tr. Ent. Soc. Lond., 1913, pt. 3, p. 423. 



