Distinguishing between two sympatric species, Bactrocera occipitalis and B-philippinensis (Diptera: Tephritidae), based on aedeagal length

A simple method based on the length of aedeagus was applied to identify fruit ny males on Guimaras Island, Philippines, where 2 species of Bactrocera are are sympatric. Males with aedeagal length of <2.81 mm are Bactrocera occipitalis (Drew & Hancock), and those of >2.89 mm are B. philippinensis (Drew & Hancock). It was notable that the length of the aedeagus is not strongly affected by the body size. The relationship between descriptive scores based on 6 characters and aedeagal length indicated that the males that have scores of 6.0-3.0 have an aedeagal length of <2.81 mm (i.e., B, philippinensis): males with scores of 2.0-0 have aedeagal lengths of >2.89 mm (i.e., B. occipitalis); and those between 2.81 and 2.98 nun are considered hybrids of the 2 species, although its rate was very low (1.0%). However, males scored at 2.5 were composed of both species. Ultimately, 95% of B. occipitalis and 89% of B. philippinensis could be correctly identified using 2 characters, the lateral marks on tergite 4 and the depth of the wing's costal band.