| Summary: | Morphometric analysis and DNA barcoding using the 5’ region of the mitochondrial cytochrome c oxidase subunit 1 (mtCOI) gene were carried out to distinguish the fruit flies Bactrocera occipitalis (Bezzi) and B. philippinensis Drew and Hancock. Adult flies and larvae were collected from Cavite and Davao del Norte, Philippines. The larvae were reared to adulthood at the Insect Ecology Laboratory, University of the Philippines Los Baños; adults were then identified along with field-collected adult specimens. Each specimen was assigned with a numerical rating from zero to six through morphological examination, using the diagnostic key originally described by White and Hancock in 1997. For morphometric analysis, ratings zero and six were used for B. occipitalis and B. philippinensis, respectively. The following structures were analyzed: lengths of abdominal tergites/sternites, femora, tibiae, and metatarsals; as well as wing length and width. Morphometric results showed significant differences (via t-test at α = 0.05%) in tergite III, mid-femur, and the metatarsals of the 2nd and 3rd leg pairs. For DNA barcoding, genomic DNA was extracted from specimens assigned with every rating (0-2 = B. occipitalis, 3 = intermediate/hybrid, 4-6 = B. philippinensis). Using customized primers, mtCOI was amplified, sequenced, and analyzed. A phylogenetic tree was constructed using the Neighbor Joining method. mtCOI clustering did not support morphological ratings, with B. occipitalis, hybrid, and B. philippinensis samples grouped together. Low bootstrap values at certain branches suggested the lack of phylogenetic differentiation among morphological species delineations. Pairwise distances of consensus sequences ranged from zero to 0.033, which were lower than the standard threshold of 0.5% utilized for species delineation in fruit flies. Therefore DNA barcoding failed to delineate B. occipitalis and B. philippinensis.
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