Interspecific Mouthpart Length Variation and Floral Visitation in the Parasitic Wasp Genus Agathirsia (Braconidae: Agathidinae)

Abstract

Carbohydrate energy sources are known to be important for many adult parasitic wasps. Floral visitation is commonly observed, and in many groups specialized mouthpart morphology is associated with deep nectar extraction. In parasitic wasps, there are few data examining the relationship between host plant use and the length of the mouthparts. In an effort to associate mouthpart length to nectar source, pollen was identified from museum specimens of selected species of Agathirsia (Hymenoptera: Braconidae). Despite drastic differences in glossa length, the pollen of several species of Asteraceae were commonly found on specimens of various species. We infer that increased feeding efficiency, as opposed to nectar access, is the adaptive value of elongate glossae in Agathirsia. Species with short mouthparts, however, exhibited a difference from both the medium and long mouthpart categories in pollen similarity. This suggests that members of Agathirsia with elongated mouthparts are more apt to visit certain flowers compared with short-tongued species. Males and females exhibited considerable overlap of their common nectar sources and displayed similar pollen richness. Pollen richness was higher in species in the medium length category compared with the short category, but these results are confounded by the fact that the medium-length specimens were on average larger bodied.

Pollen analysis ofAgathirsiawasps

“…Wasp specimens examined were either collected in the south-western United States of America ( Figure 1A) and Mexico ( Figure 1B) by T. Pucci or were loaned from various museum collections for this research [see acknowledgements for a complete listing of collections and Pucci and Jones (2010), for a complete listing of accessions]. Insect nomenclature follows the International Code of Zoological Nomenclature (ICZN; Ride et al, 1999).…”

“…Most of the natural history information for Agathirsia species is constructed only from their morphology, collection Correspondence: Gretchen D. Jones, USDA-ARS, APMRU, 2771 F&B Rd., College Station, TX 77802, USA. E-mail: gretchen.jones@ars.usda.gov (Received 29 July 2011;accepted 30 March 2012) data and the biology of closely related groups (Pucci & Sharkey, 2004;Pucci & Jones, 2010).…”

“…Agathirsia is restricted to the arid regions of the south-western United States of America and Mexico (Pucci & Sharkey, 2004;Pucci & Jones, 2010). Most Agathirsia species are collected during August through November, after the end of a relatively wet period and the beginning of a dry period (Pucci & Jones, 2010).…”

“…Most Agathirsia species are collected during August through November, after the end of a relatively wet period and the beginning of a dry period (Pucci & Jones, 2010). Many Agathirsia species have a bee mimetic colouration and are partly or entirely orange in colour, while other species are entirely black (Pucci & Jones, 2010). They lay their eggs in the larvae of lepidopteran insects (butterflies and moths) including those that are crop pests (Pucci & Sharkey, 2004).…”

“…The small wasps of the Braconidae, such as the Agathidinae, exhibit a number of morphological adaptations for nectar-feeding such as longer mouth parts (Shaw & Huddleston, 1991;Jervis, 1998). Pucci and Jones (2010) conducted an initial entomopalynological study of Agathirsia focused on examining the relationship among different mouthpart sizes to plant taxa. The purpose of the present study was to determine what plants were important to Agathirsia wasps, to establish base line entomopalynological data for this genus, and to suggest, which plant taxa would increase their numbers for the control of insect pests in cropping fields of arid regions.…”