Material and methods

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

2. Material and Methods

Geographic scope. Our keys deal with the fauna of eastern Canada (Atlantic provinces west to the Ontario-Manitoba border), and the northeastern United States south to Virginia and west to Minnesota, Wisconsin, Illinois and Kentucky. In some cases keys are applicable to more inclusive areas (e.g., eastern Nearctic for Dolichovespula) because no additional species occur outside the core area of the Atlas. Data for occurrence outside Canada are largely based on the literature, though many new state records are provided to document extensions of previously known ranges.

Species identification. Compared to other groups of aculeate wasps, Vespidae are relatively homogenous within their subfamilies and relatively poor in diagnostic characters. The resulting identification problems are further exacerbated by a high degree of variation, which is especially evident in the great variability of colour patterns. Colour characters have therefore been largely avoided in previously published keys. Colouration can indeed become almost meaningless when material from the entire range of a species is considered. Because of Müllerian mimicry different species follow common geographic trends of variation, sometimes with surprising accuracy. For example almost all yellow-marked species show red suffusion of yellow markings in peninsular Florida, and in Californian populations yellow markings generally become extremely expanded. Despite these problems, colour characters can be very useful when specimens from smaller geographic areas are considered. Some previously unrecognised species were first discovered in the course of this review because of their consistently different colour patterns. The taxonomic distinctness of these ‘colour forms’ can often be corroborated through other characters. Our keys make use of colour characters as much as possible for three reasons: (1) Colour characters are easier to assess than most morphological characters when specimens are observed in the field. (2) In a group that is generally poor in diagnostic characters one cannot afford to dismiss easily any potentially useful subset of characters. (3) While colour patterns can usually not be used for positive identifications they will help to narrow the range of possible species. However, it must be stressed that the colour characters mentioned in the key can only be used within the area covered by this work. The variation of colour patterns was usually studied on a large number of specimens, and is described in detail in the ‘Variation’ section under each species.

Taxonomy and classification. Our classification largely follows the most recent literature for each group (references listed under group headings in Taxonomic treatment), although two subspecies are reinstated as good species, and one subspecies is newly elevated to species rank. Six undescribed species discovered during the preparation of this work will be described elsewhere. The senior author is responsible for all taxonomic data and their interpretation.

Species treatments. Every species included in the keys is illustrated by a set of standard pictures including head (frontal view) and habitus (dorsal and lateral views). Because of pronounced sexual dimorphism, images of the head are provided for both sexes (including both workers and queens in Vespinae). For habitus photographs only one image of each sex (e.g., male lateral, female dorsal) was taken for species in which sexual dimorphism is low to moderate. For strongly dimorphic species the full set of images is provided for both sexes (in Vespinae also for both female castes). Variation of colour patterns, which is often considerable, is usually not documented by additional images but is described in detail in the ‘Variation’ section under each species.

Recommended techniques for killing and preparing specimens. Specimens are normally killed in the field using killing bottles charged with cyanide or ethyl acetate and pinned shortly thereafter. If these killing agents are not available specimens can also be collected into individual vials and killed later by freezing. Specimens should not be kept in cyanide bottles for too long because prolonged exposure to cyanide (especially at elevated temperatures) causes a reddening of yellow pigment in the cuticle. Cyanide-reddened areas usually show a different hue of red than areas that are originally red but can still cause confusion when keying out a specimen. In some groups, especially in the genera Stenodynerus, Parancistrocerus, Euodynerus, Ancistrocerus and Vespula, the male genitalia offer very useful diagnostic characters and thus should be pulled out and exposed when the specimen is being pinned. This can be achieved easily by reaching in between tergum and sternum 7 with a pair of fine forceps. Dissection of dry material with unexposed genitalia is very time-consuming and often causes damage to delicate structures.

Material examined. The present study is based on material from the following collections (acronyms given in parentheses): University of Guelph, Department of Environmental Biology, Guelph, Ontario (DEBU), Canadian National Collection of Insects, Ottawa, Ontario (CNCI), American Museum of Natural History, New York, New York (AMNH), Royal Ontario Museum, Toronto, Ontario (ROME), Florida State Collection of Arthropods, Museum of Entomology, Gainesville, Florida (FSCA), Sam Droege collection (USGS Patuxent Wildlife Research Center, Beltsville, Maryland), Laurence Packer collection, York University, Toronto, Ontario (PYU), United States National Museum of Natural History, Washington, D.C. (USNM); J.B. Wallis Museum of Entomology, Department of Entomology, University of Manitoba, Winnipeg, Manitoba (EDUM), Lyman Entomological Museum, McDonald College, McGill University, Ste-Anne-de-Bellevue, Quebec (LEMQ), British Museum of Natural History (BMNH), and the private collection of Brad Arnal and Harold Duggan, Waterloo, Ontario (BAR).

Photography. High resolution images (most figures in this Atlas) were taken with a Microptics Digital Lab XLT imaging system using a Canon EOS-1Ds camera and Microptics ML-1000 flash fibre optic illumination system. Each final image was assembled from a series of photographs (with different focal planes) using the computer freeware CombineZ (Hadley 2005, 2006). Images of larger specimens (mostly habitus photographs of Vespinae and Polistinae) were taken with a Nikon D70 digital camera using a Sigma 105 mm lens and Nikon SB800 or Nikon R1C1 flash. Light diffusers were used with both setups. Dissected genitalia were photographed in glycerine using either the Microptics system (see above) or a Zeiss compound microscope with Nikon Coolpix 4500 camera (images digitally stacked with CombineZ). Imaged specimens are mostly deposited in the Guelph Insect Collection except for some specimens (indicated in the Appendix) that were kindly provided by the AMNH, CNCI, ROME, USNM and FSCA.
Many species are also illustrated with field photographs, mostly taken using a Nikon D70 digital SLR camera with either a 105mm or 60mm macro lens and usually with a single remote flash. Some photographs of live specimens were taken with older, film cameras and scanned from slides for use in this Atlas.

Copyright. The copyright for photographs of museum specimens and line drawings lies with the authors. The copyright for most photographs of live specimens, unless stated otherwise, lies with Steve Marshall. Forty-one images of live specimens were kindly provided by other contributors (most of these images are posted on the website Bugguide). The copyright for these pictures lies with the individual contributor (noted on image), namely Perry Babin, Tom Bentley, Patrick Coin, Jack Connor, Johnny Dell, Tony DiTerlizzi, Bill DuPree, Bobby Grizzard, Jeff Hollenbeck, Stephen Luk, Brian Malow, Charles Matson, Sean McCann, Tom Murray, Richard Orr, Loren Padelford, Lynette Schimming, Steve Scott, Edward Trammel, Charles Weber, Machele White, and Hartmut Wisch.

Arrangement of figures and plates. In the PDF version the figures for each chapter are assembled in plates either at the end of the respective chapter (Sections A, General, and B, Keys to subfamilies, genera and species) or after the species treatments for each genus (Section C, Taxonomic treatments). Chapters are numbered starting from 1 in each of the main sections A to C of the Atlas (see Table of contents). The figure numbers are based on the section and chapter, i.e., Fig. B3.11 is Figure 11 in chapter 3, (Key to Ancistrocerus species), of section B (Keys). In citing figures, the letter pertaining to the section is only given if the figure referred to is not part of the same section (e.g., if a figure from the species treatments in section C is referred to within the keys in section B). Specimen data for each image are given in F, Appendices: Image data.

Abbreviations. The abbreviations for provinces and territories in Canada and for states in the U.S. are largely the same as the ones used by the postal systems of both countries (except we distinguish between Newfoundland and Labrador).
Canadian provinces and territories: AB – Alberta, BC – British Columbia, LB – Labrador, MB – Manitoba, NB – New Brunswick, NF – Newfoundland (excluding Labrador), NS – Nova Scotia, NT – Northwest Territories, NU – Nunavut, ON – Ontario, PE – Prince Edward Island, QC – Québec, SK – Saskatchewan, YT – Yukon Territory.
States of the United States: AK – Alaska, AL – Alabama, AR – Arkansas, AZ – Arizona, CA – California, CO – Colorado, CT – Connecticut, DC – District of Columbia, DE – Delaware, FL – Florida, GA – Georgia, HI – Hawaii, IA – Iowa, ID – Idaho, IL – Illinois, IN – Indiana, KS – Kansas, KY – Kentucky, LA – Louisiana, MA – Massachusetts, ME – Maine, MD – Maryland, MI – Michigan, MN – Minnesota, MO – Missouri, MS – Mississippi, MT – Montana, NC – North Carolina, ND – North Dakota, NE – Nebraska, NH – New Hampshire, NJ – New Jersey, NM – New Mexico, NV – Nevada, NY – New York, OH – Ohio, OK – Oklahoma, OR – Oregon, PA – Pennsylvania, RI – Rhode Island, SC – South Carolina, SD – South Dakota, TN – Tennessee, TX – Texas, UT – Utah, VT – Vermont, VA – Virginia, WA – Washington, WI – Wisconsin, WV – West Virginia, WY – Wyoming.

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