AMIERICANt MUSEUM Novitattes PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 3224, 39 pp., 26 figures April 6, 1998 A Generic Key to the Nests of Hornets, Yellowjackets, and Paper Wasps Worldwide (Vespidae: Vespinae, Polistinae) JOHN W. WENZEL' ABSTRACT The 31 genera of Vespinae and Polistinae tary Hymenoptera with which they may be con- worldwide are identified in a key to nest struc- fused. Many characteristics are illustrated or de- ture. Fifty-nine couplets and more than 80 pho- scribed here for the first time, with notes on tographs and illustrations permit both special- both anomalous species and anomalous forms ists and amateurs to recognize these nests in the of nests of common species. Pertinent published field or museum collections. A brief overview figures and museum collections are cited to explains the distinction between nests of these assist the professional in finding reference ma- social wasps and those of other social or soli- terial. INTRODUCTION All over the world, both entomologists and female (Wenzel, 1987) or millions (Zucchi et the lay public recognize and fear colonies of al., 1995). The aggressive, boldly striped social wasps. More than 900 species range adults advertise their unforgettable stings, from the Arctic to Tasmania, from prairie to and many moths, flies, and other defenseless rain forest to desert, from pristine habitats to insects have developed elaborate morpholog- industrial cities. Their sophisticated, all-fe- ical and behavioral mimicry to benefit from male societies provided the inspiration for a general desire among most animals to several of the major discoveries in insect be- avoid wasps. In addition to supporting these havior and sociobiology (Wilson, 1971: 7). mimicry complexes, their large numbers Mature colonies may consist of a single make wasps important predators of other in- ' Assistant Professor of Entomology, Department of Entomology, The Ohio State University, Columbus, Ohio. Copyright C) American Museum of Natural History 1998 ISSN 0003-0082 / Price $6.30 2 AMERICAN MUSEUM NOVITATES NO. 3224 sects in many ecosystems, composing up to or plant resins. Soil or glandular secretion about 6% of total insect biomass (Fittkau and may be used to reinforce or repair nests, but Klinge, 1973). They are well known for sym- they rarely constitute the primary building bioses with each other (Windsor, 1972) and material for mature colonies. Brood combs with other organisms such as ants (Espelie are usually one sided, with an hexagonal ar- and Hermann, 1988), honeydew insects (Le- rangement of cells sharing thin (less than 0.5 tourneau and Choe, 1987), and birds (Hind- mm) walls. There are no specialized storage wood, 1955, Joyce, 1993, Dejean and Fotso, chambers, but one may find honey or prey 1995). This commensalism attracted artists ants and termites stored in ordinary brood of ancient civilizations (Coe, 1982) and cells or in spaces between envelope sheets. forms the foundation of the mythology and In Southeast Asia, nests of Stenogastrinae rituals of certain indigenous peoples (hover wasps) may be confused with those (Schoepf, 1990). The architecture of wasp of Vespinae and Polistinae, but stenogastrine nests has been cited for its perfection as ev- nests can be separated by the following char- idence against modem evolutionary theory acters: cells more than 1.3 times as large as (Anon., 1986). Yet, despite this rich resource the head diameter of the wasp; cells usually wasps provide for behaviorists, ecologists, narrowed at their openings by a short collar anthropologists, and others, identifying and may be closed with carton by the adults wasps to genus has always required the care when the larva pupates; pupae naked and of a few overburdened specialists with ex- leaving no cocoon inside the cell; carton tensive libraries and reference collections. fragile and brittle; nest lacking a narrow, The present key to nests is offered to provide tough pedicel (although sometimes produc- an alternative that will be useful to specialists ing illusion of one by hanging from rootlets, and amateurs alike. fungal hyphae, or other such substrate); cells The wasps' industriousness as builders and sometimes connected to the substrate along cleverness as architects are appreciated even their side walls; and cells easily separated by those of us who dread unexpectedly dis- from the substrate (except when built of covering them making their home in the shel- clay). In contrast, Vespinae and Polistinae ter of our own. Their elegant paper nests build cells barely larger than the head di- sometimes attract attention as decorative cu- ameter of the wasp; cell openings not nar- rios in markets. These nests can be the size rowed by a collar nor closed over pupae by of a thimble or more than a meter long, as adults (occasionally closed in some Vespa) durable as hard felt or more fragile than egg but rather capped by a portion of the silk shells, more regular and uniform than the cocoons found in the cells; carton either frag- much-celebrated honeybee comb or wildly ile and brittle or tough and supple; nest with chaotic with an intricate mazelike interior. In- or without pedicel (mostly with pedicels in deed, variation in nest architecture between Southeast Asia); cells rarely connected to the distantly related species is far more striking substrate along their side walls; and, in living than is the morphological variation, and colonies without pedicels, cells usually not some species were initially sorted into certain easily separated from the substrate. genera primarily based on their nests. Recent Nests of a few more distant relatives of treatments demonstrate that architecture-re- Vespinae and Polistinae may be confused lated behaviors are particularly useful at trac- with them occasionally. The eumenine gen- ing phlyogenetic lineages in many animals era Zethus and Calligaster build clusters of (Wenzel, 1992a) and that architectural details cells of resin and plant material, often with of wasp nests reflect well the relationships pieces cut from leaves, but each of these bar- derived from morphological study (Wenzel, rel shaped cells has its own thick walls rather 1993). than sharing thin, common walls with neigh- The nests of Vespinae (hornets and yello- boring cells, and rarely are all cells parallel. wjackets) and Polistinae (paper wasps) are Clay nests of the Neotropical sphecids Try- easy to recognize. Except for four Neotrop- poxlyon fabricator, T. maraballi, and some ical species that build nests of mud, the nest other species may be confused occasionally are all made of vegetable fiber without wax with those of paper wasps, but the former are 1998 WENZEL: NESTS OF SOCIAL WASPS 3 naked combs of closely adjacent, circular whatever means, be accompanied by a cells each with its own walls, built without a change in architecture in one or both descen- pedicel, and often plastered with mud on the dant lineages. Eberhard's (1990: 342) ap- sides of the comb. Social vespid nests built praisal that apparent species specificity of in cavities have an entrance that is a simple spider webs is an illusion due to lack of data hole or crack, never an entrance tube of resin probably applies to wasp nests as well. Intra- as found in stingless bees, for example, Tri- specific variation between habitats or popu- gona or Melipona (Apidae). Carton nests of lations can be great, and limited sampling ants are usually composed of a coarse uneven may lead to generalizations that are false or envelope only, and never include a hexago- hold for only one part of the species' range. nal comb. A few Neotropical polistines live The illustrations offered are only to assist inside the carton nests of ants or termites, the user in deciding if he or she has found and observers should take care not to confuse roughly the right description of the nest. the structures built by these latter with the Nests are far more variable than are the mor- parallel, naked, carton combs of the wasps phologies of the animals who build them, that will be found within a cavity. and some identifiable nests will not match Museum nest specimens are often de- closely the figure chosen to characterize the cayed, discolored, distorted, lacking parts, or genus. Problematic nests, such as those in- confused with parts and adults of other nests. cluded among the diverse architectural forms Therefore, one must be cautious in certain of Paleotropical Ropalidia, are sometimes decisions, such as whether a given specimen best determined by excluding the other pos- naturally lacks an envelope or has merely sibilities (i.e., the nest does not resemble Pol- lost it in handling. I have made use of bio- istes, Belonogaster, Polybioides, or Parapo- geographic and other information that will lybia). In the neotropics the number of alter- help identification in the field or with prop- natives is much larger, and several genera erly labeled material, but some information, present problems due to their diversity of such as "in a cavity," may not be evident in nest forms or a superficial resemblance to museum specimens. Although some nests other taxa. Parachartergus includes forms have survived two centuries in collections similar to Leipomeles and Chartergellus. (Wenzel, 1992b), I do not recommend bor- Protopolybia and Agelaia both have forms rowing nest specimens from museums be- that may resemble other genera, depending cause they are bulky and travel poorly, and on the exact details of the site and colony there is generally little the novice will gain size. Pseudopolybia sometimes superficially from examining a specimen that could not resembles Vespinae (but fortunately the most have been learned from published accounts. similar forms are allopatric). Some nests of This is the first effort to include all 31 gen- Polybia can be separated from Brachygastra era of Vespinae and Polistinae worldwide.