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HYMENOPTERA, Trigonaloidea, Trigonalidae Description &
Statistics
Trigonalidae are parasitoids of Vespidae or of parasitoids of
caterpillars. Some species are
primary parasitoids of the larvae of sawflies. The females deposit their eggs on foliage. In species attacking caterpillars, the
eggs hatch when consumed by a caterpillar, and the trigonalid larva attacks
the ichneumonid, tachinid or other parasitoid larva present within the
caterpillar. In those attacking
vespoid larvae, it is believed that a caterpillar, which in turn is eaten by
a vespid wasp, consumes the eggs.
When regurgitating the caterpillar and feeding it to its young, there
is a transfer of the trigonalid larvae from the caterpillar to the wasp larva. All members of this superfamily are small, and rather rare. There
were less than 5 species kinown in North America as of 2000. Trigonalids are small and usually
bright-colored and rather sturdy.
They have the appearance of wasps, but their antennae are longer with
at least 16 segments (Mason 1993) Discussion This is one of the more
unusual families of hymenopteran insects, of unknown affinity within the suborder
Apocrita (though sometimes believed to be related to the Evanioidea), and
presently placed in its own superfamily, Trigonaloidea. Trigonalidae is
divided into two subfamilies, Orthogonalinae and Trigonalinae. These wasps
are extremely rare but very diverse, with about 94 species in over 15 genera,
and are distributed worldwide. Studies on the biology
of these insects indicates a rather unusual life history where almost all
known species have females that lay thousands of minute eggs, "clamping"
them to the edges or injecting them inside of leaves. The egg must then be
consumed by a caterpillar. Once inside the caterpillar, the trigonalid egg
either hatches and attacks any other
parasitoid larvae (including its siblings) in the caterpillar, or it waits
until the caterpillar has died and
fed to a vespid larva, which it then attacks. Therefore, they are parasitoids
or hyperparasitoids, but in a unique manner among the insects, where the eggs
must be swallowed by a host. However, there are some species that are known
to directly parasitize sawflies. References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] Townes, H.
1956. The nearctic species of
trigonalid wasps. Proc. U. S. Natl.
Mus. 106: 295-302. |