AGGRESSIVE AND COMPETITIVE BEHAVIOR OF THE FEMALE CAVE BEETLE IN THE PRESENCE OF A CONSPECIFIC MALE AND AN ALLOSPECIFIC FEMALE (BATHYSCIINAE, COLEOPTERA)

Two females of allopatric species, one of Speonomus delarouzeei (S. dl.), and one of S. brucki (S. br.), were put together facing one male of either species; 18 groups with a S. dl. male and 19 with a S. br. male were observed during 1.5 h. In controls, the female aggressiveness rate, observed in the absence of a male, is 2%. In groups, when one female meets a pair in tandem, the rate is 47% and it reaches 62% when she meets a pair in copula. The S. br. female is always more aggressive than the S. dl. female and the aggressiveness appears towards both homo- and heterospecific pairs. Furthermore females become aggressive towards males, even homospecific ones. The attacks lead to pursuits, fights, shortened matings, disrupted tandems and numerous changes of partners for the males. These observations and the important disorders already demonstrated when two males, one S. dl. and one S. br., are facing a female of either species due to a situation of sexual competition, lead one to believe that the sympatry of these two species would be henceforth impossible for behavioural reasons.