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Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region
CJAI 05, February 19, 2008
doi: 10.3752/cjai.2008.05

Matthias Buck, Stephen A. Marshall, and David K.B. Cheung

Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1

 

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21. Euodynerus annulatus (Say, 1824)
Figs B5.22, 24–26, 58; C21.1–4.

Euodynerus annulatus Euodynerus annulatus Euodynerus annulatus
Euodynerus annulatus Euodynerus annulatus Euodynerus annulatus

Species recognition. The male of E. annulatus is distinguished from all other species in the genus by the large, apically flattened, slightly expanded and obliquely truncate flagellomere XI, the slightly depressed anteroventral base of the mid femur, and the combination of a densely long-haired posteroventral surface of the hind femur and contrastingly short-haired ventral surfaces of fore and mid femur (other species with ventrally long-haired hind femur possess long hair on fore and mid femora, as well). Furthermore, the distal sterna of the male metasoma bear very dense, short erect hair (absent in most other species, present but less dense in the extralimital E. pratensis). The female is distinguished by the very long apical mandibular tooth (see key; character shared with E. crypticus). The outer margin of the tegula is more strongly angled posterolaterally than in any other species, so that the margin is almost perpendicular to the main body axis posteriorly. Euodynerus annulatus is one of five species, in which a very sparsely punctate tergum 1 contrasts with a strongly punctate tergum 2 (including discal area). It is distinguished from the other four species with smooth tergum 1 (E. hidalgo, E. crypticus, E. auranus, Euodynerus sp. G; punctation variable in latter two) by the angularly produced submarginal carina.

Variation. Fore wing length 8–9.5 mm (♂♂), 8.5–10.5 mm (♀♀). Yellow markings of head in female more or less suffused with ferruginous; female clypeus sometimes yellow and ferruginous, without black. Yellow pronotal band narrow or broad, with a ferruginous posterior border that can vary from linear to very broad (extending to posterior corners of pronotum). Spot on upper mesopleuron usually absent. Scutellum rarely with a pair of tiny yellow or ferruginous spots. Markings on propodeum yellow with narrow ferruginous border to entirely ferruginous. Metasomal terga 1–4 with yellow fasciae, in male often also terga 5 and 6; apical fasciae of sterna 2 and 3 usually reduced to lateral spots in female, complete at least on sternum 2 in male, sometimes also on following sterna up to sternum 6, but then becoming more ferruginous posteriorly. Lateral third of tergum 1 with variable amounts of yellow and ferruginous. Tergum 2 in male often, in female rarely, with a pair of ferruginous discal spots; ferruginous spots sometimes also present on male sternum 2. Legs largely ferruginous, with variable amounts of yellow.

Distribution. Canada: AB and BC, newly recorded from ON and SK. Transcontinental in U.S. (Krombein 1979). Mexico: northern Mexico, including Baja California, south to Durango (Rodríguez-Palafox 1996). Northeastern populations belong to the ssp. arvensis (de Saussure, 1870). The nominate subspecies and three other subspecies have a western distribution. Euodynerus annulatus has apparently become very rare or extirpated in Ontario with no specimens having been collected after 1954 (Essex Co., Point Pelee, CNCI).

Biology. Euodynerus annulatus is one of only two ground-nesting species of Eumeninae in the northeast that builds a chimney-like mud tube over the nest entrance (see also Odynerus dilectus). The mud tube is ca. one inch long, thick-walled and usually curved. There seems to be no particular preference for a certain soil type; nests are built in both hard and soft soils (Isely 1914). Isely found nests always in close proximity to water (usually not farther than 27m, exceptionally 91m away). While digging, females make frequent trips to water sources in order to take up water for moistening and softening the soil. Excavated soil is used for the building of mud tubes. There is also one record of the species nesting in an abandoned mud dauber nest (Isely 1914). Broods cells are provisioned with caterpillars of Crambidae, Pyralidae and “Noctuidae” (in the traditional sense) (Evans 1956, Krombein 1979).

 

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