Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region
Matthias Buck, Stephen A. Marshall, and David K.B. Cheung
Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Species recognition. This species and A. albolacteus are distinguished from the species of the A. catskill-complex by the more slender mesosoma with scutum and scutellum distinctly flattened dorsally in females. Differences between A. adiabatus and A. albolacteus are discussed under the latter. Ancistrocerus adiabatus has relatively extensive yellow markings including a complete yellow metanotal band (usually absent in males) and a yellow ventral surface of the flagellum in both sexes (sometimes obscure in females), but it lacks pale markings on the propodeum (present in females of A. catskill and A. lutonidus) on the parategula (often present in females of A. catskill), and on female tergum 6 (present in Ancistrocerus sp. A).
Variation. Fore wing length 5.0–7.0 mm (♂♂), 6.5–9.5 mm (♀♀). Pale markings usually bright yellow, in some northern males slightly pale. Female clypeus usually with a pair of dorsal and a pair of ventral spots (very rarely ventral ones absent), the spots usually confluent laterally and often ventrally as well; one xanthic female from St. John, NB (CNCI) was examined with clypeus almost entirely yellow except for the edges and a narrow black median line extending from base to middle of disc. Interantennal spot of male rarely extended to clypeal margin along interantennal carina. Yellow spot along inner orbit of male rarely interrupted opposite antenna. Yellow spot between inner orbit and antennal socket of female rarely absent. Spot on upper mesopleuron well developed in female, usually present (small or large) in male, rarely absent. Tegula exceptionally without pale markings in male. Pair of pale scutellar spots well developed in female; usually small in male, exceptionally absent. Metanotal band rarely interrupted medially in female (most of these specimens are intermediate with regard to the yellow colour form of A. albophaleratus and are tentatively identified as A. adiabatus); metanotum usually completely black or with irregular yellow markings in male, rarely with a complete band. Metasomal terga 1–(4)5 (female) or 1–(5)6 (male) fasciate (the more melanic colour frequently induced by stylopization). Female sternum 1 with more or less developed apical fascia, sternum 2 and usually 3 with complete apical fascia, the latter usually interrupted laterally, rarely reduced to lateral spots; sternum 4 usually with apicolateral spots, sometimes with laterally interrupted fascia, rarely with complete fascia; sternum 5 usually with apicolateral spots and/or median spot, rarely lacking yellow markings. In the male sterna 1–6 often with more or less complete apical fascia, often obscure on sternum 1 and sometimes on posterior sterna. In melanic specimens at least sternum 2 with complete yellow fascia and sterna 3 and 4 with apicolateral spots.
Distribution. Transcontinental in Canada and the U.S. (Krombein 1979). We have examined specimens from every Canadian province except NF/LB and AB. The western ssp. cytainus (Cameron, 1906) ranges from CO to OR and CA. The former ssp. albolacteus is tentatively treated as a species here (see below).
Biology. Breeds in borings in twigs, stems and wood, empty insect galls and sawfly cocoons, old mud-dauber nests, and rubber tubing. Cell partitions and closing plugs are made of mud. Prey consists of caterpillars of Amphisbatidae, Oecophoridae, Gelechiidae, Tortricidae and Coleophoridae (Krombein 1967, 1979).