How to Recognize a Chalcid
In order to use this handbook it is necessary first to recognize a chalcidoid. One clue is their size. Rarely are specimens much over 5mm in length.
In the field or the lab chalcidoids are most easily confused with small gnat like flies and other small wasps. Chalcidoids, being Hymenoptera, have two
pairs of membranous wings as opposed to the single pair found in flies. Among the majority of wasps, chalcidoids are noted for their much reduced wing
venation. In the forewing there are no cells that are completely surrounded by veins (see wing, p. 18; note that the "costal cell" has no vein on the forwared edge).
Most other Hymenoptera not only have several (or many) closed cells, but they have many veins on the wing as well. Chalcidoids have essentially only one vein that
is brancede at the ned (into postmarginal and stigmal) and rearely not evern this is branched. Among all wasps, chalcidoids are only likely to be confused with some
of the proctotrupoid families (especially Scelionidae and Platygastridae) because the wing venation is similar. Here the distinctions become somewhat more difficult
and technical. Most chalcidoids have a sclerite (side of mesosoma) called the prepectus between the base of the forewing and the pronotum, whereas proctotrupoids lack
this sclerite. As a result, in most chalcidoids the base of the forewing appears to be removed some distance from the lateral corner of the pronotum, but in proctotrupoids
the base appears to touch the corner of the pronotum. There is a technically more reliable character involving the position of the mesothoracic spiracle in chalcidoids
(see Gibson 1993), but it is difficult to see and its use is seldom called upon, that it is of value mostly in esoteric cases of classification. Most Chalcidoidea also have
elongate, raised sensilla on the antennae (usually seen as parallel white lines on the funicle segments), which proctotrupoids do not have. In the case of a few wingless chalcidoids, the
spiracle and sensilla re the only technically accurate methods to separate them from the proctotrupoids. Finally, it should be noted that many chalcidoids tend to be metallic in coloration
or to have mixtures of colors such as black and yellow. Proctotrupoids are never metallic and generally black.
Although a difficult task at first glance, recognizing chalcidoids is not the impossible endeavor it may appear to be. With experience, chalcidoids may be identified to family level in the field
and even on the wing. All it requires is a little practice.
Introduction to the Key
The key is designed to be "easy" to use, not necessarily absolutely technically or phylogenetically correct.
It proceeds somewhat along the mental process we sue to sort chalcidoids to family, i.e., the easily observed
characters are used first. The first alternative states the conspicuous character, and if you cannot see the character
because the specimen is too small, it usually means you should take the second alternative. All known chalcidoid
families (except for obscure Rotoitidae from New Zealand and Chile) are included (some as subfamilies). The key,
however, is based on Nearctic species so that it will not work in all instances for Old World groups even at the family level.
A few odd genera are keyed out near families other than the correct one because they appear aberrant (compared to the rest of
the family) and generally cause a key to become filled with "either-or," and "if, and, or but" type statements. Generally, the
families are fairly distinct morphologically (at least in one sex), but a few odd forms may cause a relatively simple key to
become overly complex. Our feeling is that these few odd forms may be keyed out pragmatically (or learned by sight) and removed
from the majority of species so the identification of remaining forms becomes possible without too much difficulty. We have tried to structure
the key so that all common material will run through it. Many uncommon taxa should run through it as well. Male specimens of a few families (e.g., some eupelmids, pteromalids)
will not run through the key. For males we've added additional comments in the discussion of Distinguishing Characters (not present in online version of key) to help.
The illustrations for the key are rendered in large part by Linda Lawrence and Deborah Roney. A few drawings were borrowed (with modification) from sources listed in the text and under the taxon being identified.
Introduction to the Key Online
All text and drawings are taken from the original, priceless and out of print key:
Grissell, E. E., and M. E. Schauff. 1990. A handbook of the families of Nearctic Chalcidoidea (Hymenoptera).
Entomological Society of Washington (Washington, D.C.) Handbook 1:1-85.
Addional images for the key have been added by Dr Michael Gates at the USDA-ARS Systematic Entomology Laboratory
Website created by Katja Seltmann
() with gracious help from the morphbank
crew. Key hosted by the Hymenotpera Assembling the Tree of Life Project
Funding for this project has been in part from two National Science Foundation grants: Assembling the Tree of Life Project EF-0337220
for Building the Hymenopteran Tree of Life: Large Scale Phylogenetic Analysis of the Hymenoptera
Biological Databases and Informatics (BDI) Program DBI-0446224
for Morphbank: Web Image Database Technology for Comparative Morphology and Biodiversity Research
This work is licensed under a
Creative Commons Licence
A PDF version of this key is available here