90 



been unknown. It is sufficient to examine a few adult individuals 

 and to measure the area of the pad. A formula is given for calculating 

 the relation of the area of each of the pads to that on the first pair of 

 legs multipUed by 100, this proportion being called the index. Until 

 proof has been obtained to the contrary it may be taken that an index 

 of less than 80 for the fourth pair of legs indicates an Ixodid with 

 three hosts, while an index of more than 80 for the fourth pair denotes 

 an Ixodid with one or two hosts. 



Van Saceghem (R.). Observations sur la Dermite granuleuse. 



[Notes on Granular Dermatitis.] — Ann. Bled. Vet., Brussels, Ixv, 

 no. 3, March 1920, pp. 135-136. 



A large number of cases of a form of granular dermatitis in horses 

 and donkeys in the Belgian Congo have been observed to be caused by 

 a Nematode, Filaria irritans. Both species were infested in about 

 equal numbers, the attacks beginning in October. The hfe-history 

 of the parasite is not known. 



Towards February the sores develoj) a tendency to heal, probably 

 because the Nematode has finished its evolution in the w^ound. Surgi- 

 cal treatment, at any rate in Africa, is unadvisable owing to the danger 

 of myiasis. 



Mayne (J. F.) & Jackson (W. R.). Larvicides.— JL R.A.M.C, 

 London, xxxiv, no. 2, February 1920, pp. 112-120. 



Experiments were made in Macedonia with various substances to 

 test their relative value as mosquito larvicides. The most common 

 species found include : Anopheles maculipennis, A. bifurcatus, 

 A. palestinensis {super pictus), A. pseudopictus, Theobaldialongiareolata 

 {spathipalpis), T. annulata, Culex mimeticus, C. pipiens and C. hortensis. 



The tests made with paraffin show that its action is quicker when 

 thoroughly mixed with the water than when applied as a film, owing 

 to the toxicity of the substance which directly effects the larvae. 

 Experimentally the larvae were killed in 1 hour and 20 minutes when 

 the paraffin was mixed with the water, whereas when apphed as a 

 superficial film they hved for 5 hours. The pupae on the contrary 

 are killed in \ hour when the oil is apphed as a film but survived for 

 3 days in paraffin and water. 



Cresol proved most satisfactory as a larvicide, 1 part in 1 million 

 or even 1 in 10 million being sufficient to kill all larvae of Cidex, 

 Anophehnes requiring rather stronger solutions. The water con- 

 taining such a small amount of poison is probably innocuous. Pupae 

 are more resistant to cresol than larvae, but it was specially eft'ective 

 against the egg-rafts, the minute larvae on hatching being Icilled by 1 

 part in 100 million. 



Sanitas-okol is poisonous to man and animals, and is apparently 

 not nearly so efficient a larvicide as cresol. 



Bleaching powder, although useful in an emergency in varying 

 proportion from 1 in 1,000 parts to 1 in 100,000 parts, is too unstable, 

 for general use ; carbohc acid also gave disappointing results. 



