Torymids have a wide host range with both plant and insect
eating species. As in some eurytomids, torymids associated with gall-forming
insects devour just about anything in the gall, including other parasites,
inquilines, and plant tissue. Thus some entomophagous species appear to
be fairly omnivorous, and the adult female is the factor which determines
the host range of her progeny. Torymidae is currently divided into 2
subfamilies (Grissell 1995): Megastigminae and Toryminae. Two other
families, Agaonidae and Ormyridae, have been placed in or out of the
Torymidae on various occasions. The phylogenetic position of some of the
subfamilies of Agaonidae is still in doubt, and it is possible that some
may belong to Torymidae (Grissell 1995). In the Nearctic, Sycophaginae
(often called Idarninae) was once placed in Torymidae (Grissell
1979) but more recently was transferred to Agaonidae (Boucek 1988). There
is still some debate on whether this placement is correct. The ormyrids
have often been placed as torymids because of their enlarged hindcoxa and
reduced stigmal vein, but they have also been placed as pteromalids based
upon the absence of an exserted ovipositor and the presence of "otherwise
pteromaline-like" characters (Riek 1970). Because we cannot currently
contribute any concrete alternatives, it is easier to recognize the
agaonids and ormyrids as separate families until a broader overview of the
Chalcidoidea is available. The Nearctic torymids were most recently
treated by Grissell (in Gibson, et al. 1997) and are classified as
follows:
Megastigminae: 1 genus, 25 species. The genus was revised
by Milliron (1949) who included a key to the world genera.
Toryminae: 18 genera, 147 species. Burks (1969a) gave a
key to the 3 Nearctic species of Physothorax which was
updated by Boucek (1993). Grissell (1976) arranged the 99 Nearctic species
of Torymus into 5 species groups, gave keys to these groups, and
revised the 61 western Nearctic species. The genus Monondontomerus (13
species) was revised by Gahan (1941). The Nearctic species of
Podagrionini were revised by Grissell and Goodpasture (1981).
STATISTICS: Number of world species: about 900 (200
Nearctic); number of world genera: 65 (21 Nearctic).
BIOLOGY: Megastigmine torymids, in the New World, are entirely
phytophagous, mostly within rosaceous and coniferous seeds. The major plant
genera known to host these wasps are Abies, Cedrus, Chamaecyparis,
Ilex, Juniperus, Larix, Picea, Pseudotsuga,
Tsuga, Amelanchier, Rosa, and Pistacia (an introduced
species) (Milliron 1949, Grissell 1989). In the Old World, a few entomophagous
species are known which attack Cynipidae as well as a few other gall or
seed-feeding Hymenoptera and Diptera (these records, however, are not numerous
nor particularly well documented).
Torymines are diverse biologically but most are ectoparasitic upon larvae
in galls or enclosed in plant tissue such as stems or seedpods. The most
common families of gall-forming hosts are Cecidomyiidae and Cynipidae but
Tephritidae and Psyllidae are also attacked. The larvae of many other
families of Hymenoptera and Diptera serve as hosts, as do a few families
of Coleoptera and Lepidoptera. A large number of species (all
Podagrionini) attack mantid eggs. Several species have been reared from
eggs of Lepidoptera, Heteroptera, Homoptera, and Coleoptera. A few
phytophagous species are known from Malus, Crataegus,
Ilex, and Acer seeds.
DISTINGUISHING CHARACTERS: Female torymids are fairly
easily distinguished by the exserted ovipositor sheaths which project
clearly from the metasoma. (In some specimens of other families the
ovipositor, itself, may slip out of the metasoma as a hairlike, bare
spine, but in torymids the coverings of the ovipositor (i.e., sheaths) are
permanently exserted and cannot be retracted.) The family Agaonidae is
also characterized by the exserted ovipositor sheaths but is separated
from Torymidae by the forward-projecting head and the mandibles modified
with an elongate, rasplike appendage. Unfortunately at least a few species
in almost all other families of chalcidoids have exserted ovipositor
sheaths, so that care must be taken when using this character
alone. Another character we find useful is that torymids almost always
have the stigmal vein essentially sessile (shortened) while similar
appearing (i.e., with exserted ovipositor) pteromalids and eupelmids have
an elongate stigmal vein. A character that also works well in female
torymids, but is not always readily visible, is that the cerci of the last
tergum are exserted, being longer than wide, and a small flap
(epipygium) is present at the posterior margin of the tergum. Other
chalcidoid females have the cerci more or less "bumplike." In
the few pteromalids with exserted cerci, there is no epipygium and the
ovipositor is not exserted. The aberrant tribe Podagrionini may be
characterized by its "torymid" characters, plus the enlarged
hindfemora as in the Chalcididae. Male torymids are generally less easily
separated than females (because they lack the obvious ovipositor), but the
relatively short stigmal vein and exserted cerci are often enough to
distinguish these from specimens of other families.
COLLECTING: Torymids are often swept from shrubbery or
trees, especially if galls are present. In general, there may not be much
torymid diversity on a single plant species, but often within a collecting
area one can find a diversity by collecting off different plant species.
Small-flowered composites and umbellifers are good for sweeping. Rearing
almost any type of gall will usually yield a few (or many) torymids.
DISTRIBUTION: Megastigmines are predominantly of northern
distribution. Torymines are found throughout the world in small
numbers, except for the speciose genus Torymus, which is
essentially Holarctic in distribution.
