182 . 



The adult female is an inveterate blood-sucker, attacking cattle, 

 horses and mules, but not apparently human beings. The attacks are 

 remarkably persistent, the flies being considered in some districts to 

 be responsible for the death of their hosts. It is not known whether 

 death has been caused by continued loss of blood from the many lesions, 

 by suffocation due to the animals inhaling the swarming insects with 

 resulting obstruction of the bronchi, by the injection of some toxic 

 substance produced in the salivary glands, or owing to the presence 

 of a pathogenic micro-organism of which the fly may be the vector. 

 Investigations into the last possibility have given entirely negative 

 results. 



Development of the ovaries of S. simile seems to depend upon the 

 ingestion of a blood-meal, and at least ten days must intervene after 

 full engorgement before they are completely developed. Whether the 

 flies may become engorged and oviposit more than once is difficult to 

 determine, as the females are not easy to experiment with in captivity, 

 but the presence of both mature and immature eggs in the ovaries of 

 individuals that have completely digested a blood-meal is considered 

 significant. 



The nymphs of may-flies, particularly Heptagenia sp., feed exten- 

 sively on the larvae of 5. simile and considerably reduce their numbers. 

 Stone-fly and dragon-fly nymphs also devour them. The most 

 important enemy, however, is the sucker-fish, Catastomiis commersonii, 

 which feeds almost exclusively on larvae and pupae of S. simile. 



The only measure that promises any success in the control of the 

 flies is the use of repellents on the animals. Besides those previously 

 suggested \loc. cit.'\, a mixture of 2 gals, kerosene with \ lb. soft soap to 

 1 gal. of water is recommended, 1 part being used to 5 parts of water as 

 a spray. An alternative is a mixture of 2 parts pulverised resin, 1 part 

 soap shavings, \ part water and 1 part fish-oil, which are boiled together 

 until the resin is dissolved ; 1 part oil-of-tar, 1 part kerosene and 

 3 parts water are then added, and the whole stirred and boiled for 

 fifteen minutes. When cool this can be used as a spray, but the 

 objection to either spray is that applications are necessary at least 

 once or twice each day, while the oily mixtures tend to make the 

 animals very dirty. Phinotas oil is effectual in kifling the larvae by 

 contact, but the use of miscible oil is scarcely practicable in the swift- 

 running rivers. 



Adult females of the small-stream species, S. venustum and S. vittatum, 

 are also blood-suckers ; these species can more easily be dealt with in 

 the larval stage by the oiling method. 



Crawley (H.). A Case of Demodectic Mange in a Bull, — //. Amer. 

 Vet. Med. Assoc, Washington, D.C., Ixi, N.S. xiv, no. 4, July 1922, 

 pp. 441-443, 1 fig. 



A case is recorded of Demodex bovis being taken from pustules on 

 the skin of a pure-bred Guernsey bull in Pennsylvania, the organisms 

 being present in great numbers. Cows of the same herd did not appear 

 to be infested with mange mites of any kind. Records of the occurrence 

 of Demodex in cattle are rare ; it has been found in Nyasaland 

 [R.A.E.,B, iii, 119] and in American cattle (Canadian Entomologist, 

 1892), but in view of the present finding the condition may be much 

 commoner than has been supposed. 



