Development rates of two Xenopsylla flea species in relation to air temperature and humidity

The rate of development of immature fleas, Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild (Siphonaptera: Xenopsyllidae) was studied in the laboratory at 25 degreesC and 28 degreesC with 40, 55, 75 and 92% relat ive humidity (RH). These fleas are separately associated with the host jird Meriones crassus Sundevall in different microhabitats of the Ramon erosion cirque, Negev Highlands, Israel. This study of basic climatic factors in r elation to flea bionomics provides the basis for ecological investigations to interpret reasons for paratopic local distributions of these two species of congeneric fleas on the same host. Both air temperature and RH were pos itively correlated with duration of egg and larval stages in both species. Change of humidity between egg and larval environments did not affect durat ion of larval development at any temperature. At each temperature and RH, t he eggs and larvae of X. ramesis did not differ between males and females i n the duration of their development, whereas female eggs and larvae of X. c onformis usually developed significantly faster than those of males. For bo th species, male pupae developed slower than female pupae at the same air t emperature and RH. Air temperature, but not RH, affected the duration of pu pal development. At each humidity, duration of the pupal stage was signific antly longer at 25 degreesC than at 28 degreesC: 15.3 +/- 1.7 vs. 11.7 +/- 1.2 days in X. conformis; 14.1 +/- 2.0 vs. 11.5 +/- 1.7 days in X. ramesis, with a significantly shorter pupal period of the latter species at 25 degr eesC. These limited interspecific bionomic contrasts in relation to basic c limatic factors appear insufficient to explain the differential habitat dis tributions of X. conformis and X. ramesis.