Host associations of Bracon mellitor Say (Hymenoptera: Braconidae) in native vegetation in central Texas

Abstract

Alternate hosts of Bracon mellitor Say were located in native vegetation in College Station and New Clarkson, TX. Six new hosts, Acontia cretata (Grote & Robinson), Phalonia sp. (A), Phalonia sp. (B), Anthonomus heterothecae Pierce, Mimoschinia rufofascialis (Stephens), and Schinia mitis (Grote) were discovered. Associations between these hosts and B. mellitor were studied. Previous records of alternate hosts of this parasitoid are reviewed. Seasonal occurrence and abundance of B .mellitor, its hosts, and their host plants were studied at New Clarkson, TX in 1983. From this information a conceptual model of plant sequence of B. mellitor is proposed. The plants Cirsium texanum Buckley and Pyrrhopappus multicaulis de Candolle are important for the survival of this parasitoid because these plants harbor insect hosts in the early spring when parasitoids begin to emerge from their overwintering sites. Grindelia squarrosa (Pursh) Dunal and Heterotheca latifolia Buckley are also important in that they are refuges for overwintering individuals of B. mellitor. Host size was found to affect sex ratio and adult size of B. mellitor. A greater percentage of males than females developed on small hosts such as A. heterothecae. Differential oviposition of male and female eggs accounted for the variances in sex ratio with differences in host size. It was determined that smaller B. mellitor adults developed from smaller insect hosts. Age-specific life-tables for this parasitoid on 4 hosts, Anthonomus grandis, Phalonia sp. (A), Phalonia sp. (B), and an unidentified curculionid from Abutilon fruticosum, were calculated. Generation mortality of B. mellitor was lowest (15.6%) for immatures developing on A. grandis Boheman than for those individuals developing on the other 3 host species studied. Adult size of B. mellitor affected female longevity and fecundity and mating success between males and females. Longevity and fecundity were greater for large females than for very small females. Fifty-five % of the exposures of small females to large males resulted in successful matings. However, 86% of, the exposures of large females to small males resulted in successful matings...