Information transmission during intra- and interspecific courtship in Ephestia elutella and Cadra figulilella

Using information theory, courtship posturing in the moths Ephestia elutella (Hübner) and Cadra figulilella (Gregson) was analyzed for information transmission, which was partitioned into autocovariability (intraindividual transmission) and cross-covariability (interindividual transmission). This two-factor analysis was sufficient to account for more than 60% of the behavioral variance in males of E. elutella and in both sexes of C. figulilella during intraspecific courtships; however, there were large residual variances in the behavior of male and female C. figulilella during interspecific courtships and in E. elutella females during both inter- and intraspecific courtships. In E. elutella, significant levels of transmission were attributable to both inter- and intraindividual effects, whereas in C. figulilella, only autocovariability was high and no interindividual communication could be assigned to courtship postures. Although courtship in these two species was qualitatively very similar and males readily courted nonconspecific females, high levels of reproductive isolation resulted from courtship. Male C. figulilella had 94% fewer copulations with E. elutella females than with conspecific females and E. elutella males had 78% fewer copulations with C. figulilella females than with conspecifics. These reductions were due to a differential response in both females and males, causing inter-specific courtships to be terminated much earlier than intraspecific courtships. This discrimination indicates that interindividual communication was indeed occurring during courtship and was only partially measured by analysis of postures. Thus, communication took place largely in some other modality, most likely the chemical modality, where species specificity is suggested for both male and female pheromones.