Distinguishing between the Two Sympatric Species Bactrocera carambolae and B. papayae (Diptera: Tephritidae) Based on Aedeagal Length

Abstract

Aedeagal length was measured to distinguish among fruit fly males in Singapore, where 2 closely related species, Bactrocera carambolae (Drew & Hancock) and B. papayae (Drew & Hancock), are sympatric. Although aedeagal length did not segregate into 2 distinct distributions, when it was plotted against body size, males could be divided into 2 groups, those with shorter aedeagus (S-group) and those with longer aedeagus (L-group). The aedeagal length of the S-group ranged from 2.39 to 2.68 mm, and that of the L-group from 2.66 to 3.34 mm. Thus, the 2 groups overlapped between 2.66 and 2.68 mm. To clarify the relationship between aedeagal length and other morphological traits, the transverse black band on tergite 4 was categorized into 4 types, A, A', B', and B. Also, costal band depth at the apex of the wing was categorized into 4 types, 4, 3, 2, and 1. Although the S-group was composed of band types A/A', the L-group included all 4 band types, indicating that males in Singapore can be categorized into 3 groups, types A/A' of S-group (Sa), types A/A' of L-group (La), and types B/B' of L-group (Lb). It was noticed that all of the Sa type had wing types 4/3, whereas the La type was characterized by wing types 2/1, except for 1 male of band type A' which had wing type 3. Therefore, it is judged that the Sa type is B. carambolae and both the La and Lb types should belong to B. papayae.