Reproductive Incompatibility Between Host Strains of the Fall Armyworm (Lepidoptera: Noctuidae)

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Abstract
Laboratory crosses between two host-associated strains of the fall armyworm, Spodoptera frugiperda (J. E. Smith), were performed to determine if pre- or postreproductive incompatibilities existed. Two sets of experiments were conducted, the first (in October 1985) using a pair of fall armyworm strains from Puerto Rico, and the second (in September 1986) using a pair of strains from Louisiana. The same incompatibility was observed in both experiments. No successful matings occurred between females of the “corn strain” and males of the “rice strain,” and dissections of those females indicated that no spermatophores had been transferred. The reciprocal crosses between rice-strain females and corn-strain males resulted in fertile F1 progeny that were reared to adulthood and backcrossed to parental strains. No progeny were produced in backcrosses involving F1 females, but interbreeding did occur between F1 males and parental females and between a few interhybrid (F1 × F1) crosses. These results indicate that premating reproductive barriers exist at some stage in both crossing directions between fall armyworm strains, and support the contention that “fall armyworm” is composed of host-associated sibling species.