[Effect of certain factors on block formation in Ceratophillus tesquorum and Neopsylla setosa setosa].

Studies were conducted of the effect of temperature and humidity, variant of plague microbe, frequency and duration of feeding and specificity of the host on the blockformation in the souslik fleas C. tesquorum and N. setosa infected with plague. 28 tests on the effect of temperature and humidity on the blockformation were undertaken, for which 14411 fleas of the above species were used. A temperature of 16 to 22 degrees proved to be optimal; at this temperature the number of blocked fleas (C. tesquorum) varied from 21.2 to 42.7% and that of N. setosa--from 41.9 to 54.2%. Marmot variant of plague microbe caused the formation of the "block" in 53.3 to 55.1% of fleas of N. setosa in 3-4 days and in 28.0 to 42.7% of C. tesquorum in 10-14 days after the infection. In C. tesquorum the process of blockformation is affected by the frequency of feeding, in N. setosa--by the duration of each feeding.