J, HYM. RES. Vol. 7(2), 1998, pp. 178-181 Sexual Dimorphism Of Wasp Antennal Structure in Relation to Parasitic and Non-parasitic Behavior (Hymenoptera: Sphecidae) William T. Wcislo Smithsonian Tropical Research Institute, Balboa, Republic of Panama (Address for correspondence; Smithsonian Tropical Research Institute, Unit 0948, APO AA 34002-0948, USA; E-mail,
[email protected]) Abstract. — To assess the relationship between sensory ecology and behavior of non-parasitic and parasitic spheciforme wasps (Sphecidae), I measured the lengths of scapes, flagella, and body size (intertegular distance) of males and females of 29 species, representing 7 subfamilies and 26 tribes. Unlike a previous study with bees (Wcislo, 1995), spheciforme wasps show no consistent sexual dimorphism in relative antennal size for free-living versus parasitic species. Brood parasitism (cuckoo behavior) and social parasitism have evolved repeatedly among bees, aculeate wasps and ants (e.g., Wcislo 1987; Wcislo and Cane 1996; H611-dobler and Wilson 1990; Cervo and Dani 1996). Parasites utilize host-derived re-sources (a nest, stored food, or worker la-bor) to rear their own offspring. Maternal behavior of parasitic and non-parasitic species differs (Wcislo 1987), while respec-tive males do not differ essentially in mat-ing behavior, although data are scant (e.g., compare Cederberg et al. 1984 with Al-cock and Alcock 1983). Few studies have investigated the sensory ecology (sensu Dusenbury 1992) of parasitic and non-par-asitic Aculeata to ascertain if differences in sensory structures co-occur with behavior-al differences. Non-parasitic bees (Apo-idea) usually are strongly sexually dimor-phic for antennal structures; at a given body size, males tend to have shorter scapes and longer flagella (Wcislo 1995; Miiller 1872). Parasitic bees, in contrast, usually are not sexually dimorphic for rel-ative size of antennal structures. Among ants, a fusion of antennal flagellomeres is part of a syndrome of structural characters associated with parasitic behavior (Holl-dobler and Wilson 1990). Some clades of spheciforme wasps ( = "Sphecidae" of Bohart and Menke 1976) together with the bees form a monophy-letic group, Apoidea (e.g., Alexander 1992; Brothers and Carpenter 1993). Parasitism has evolved repeatedly in bees (e.g., Wcis-lo and Cane 1996), and has probably evolved twice among spheciforme wasps, once in the common ancestor of the genus Stizoides and once in the common ancestor of Nyssonini (see Bohart and Menke 1976). Thus, the evolution of parasitism among sphecid wasps provides additional exam-ples to assess whether female parasites are similar to males in their sensory ecology and relevant structures. This note presents information on antennal size for parasitic and non-parasitic wasps (Sphecidae), as part of an on-going comparative study of the relationship between morphological and behavioral evolution within aculeate Hymenoptera (cf. Wcislo 1989). MATERIALS AND METHODS In an effort to minimize phylogenetic bias I used 29 species, representing 7 sub-families and 26 tribes of the 10 subfamilies and 30 tribes that Menke (1997) lists for Sphecidae (see Appendix). Intertegular distances, scape length, pedicel length.
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