Chemically Mediated Reproductive Isolation between Cabbage Looper and Soybean Looper Moths (Lepidoptera: Noctuidae)

Abstract

In release-recapture studies, male cabbage looper (CL), Trichoplusia ni (Hübner), and soybean looper (SBL), Pseudoplusia includens (Walker), moths readily distinguished between and responded selectively to their respective conspecific females. Consequently, most males were recaptured in traps baited with conspecific females, fewer with both females in combination, and the least with heterospecific females. Actographic analysis indicated that males tend to fly more frequently in the presence of conspecific females and that males arrest female activity. CL males also arrest the movement of SBL males and females. Although CL and SBL males flew to calling females of both species in an observation chamber, only the CL females aggressively rejected courting SBL males. Thus, before courtship, CL and SBL females stimulate and attract discriminating males that subsequently arrest the movement of females and probably that of competing males.