Sexual dimorphism and sex ratio of alfalfa longhorn beetle (Plagionotus floralis Pall.) (Coleoptera: Cerambycidae)

摘要

In Bulgarian entomological literature, there is little information of alfalfa longhorn beetle, which necessitates the addition of new data about the pest. In the alfalfa fields and the laboratory of entomology of IASS "Obraztsov chiflik" - Rousse, during the period 2010-2015, observations and measurements were made on adult insects with aim to establish clear morphological features for sex recognition and sex ratio calculation.The length of the body, the width of the pTothorax and the weight of the female and male individuals were measured. The sex ratio was calculated by Bremer's formula. Sexual dimorphism was clearly detected to be expressed in length and weight of female insects (13,81 mm and 0,062 mg) were proven to be bigger compared to male insects (13,00 mm and 0,05 mg); different antenna lengths; differences in the color of the scapus, coxa, trochanter and femur of the three leg couples in female and male individualswere detected.The sex ratio of alfalfa longhorn beetle was in favor of females in two of the years surveyed (61.34% -63.64%), while the remaining four of the years in the species population dominated males (60.72% -75.00%).