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HYMENOPTERA, Sphecidae
(Crabroninae) (Sphecoidea) -- >Images> &
<Juveniles> Description &
Statistics
The subfamily Crabroninae contains a large number of species of
small parasitoids that build their nests in hollow stems, burrows in the soil
or abandoned wood galleries. The
latter are usually those of beetle borers, and may be further enlarged by the
new occupant to provide cells for its brood.
The nests are of two types, one being linear and consisting of a row
of cells, the second having lateral galleries branching from the main
tunnel. Prey are exceedingly varied,
ranging from mites and spiders to adult Coleoptera, Diptera, Homoptera,
Ephemeroptera, Lepidoptera, Hymenoptera and Diptera (Clausen 1940/1962). The subfamily is not wholly beneficial
because of the attack on spiders and some parasitic and predaceous
Hymenoptera and Diptera. Syrphid
flies are frequently attacked, and in Europe Lindenius pygmaeus
Rossi provisions its cells with chalcidoids of the genus Pteromalus. There is no
obvious consistency in the selection of prey by the various species, as the
species of a single genus may utilize Diptera, Hymenoptera or
Coleoptera. A single parasitoid
species may limit itself to only one sex of the host, while the opposite
extreme is found in examples of species preying on several orders (Hamm &
Richards 1926). The first cell to be provisioned is that one situated farthest from
the nest entrance, and the egg is usually laid on the first prey placed in
each cell. However, in Crabro brevis Lind. oviposition occurs only after the full complement of
beetles has been stocked in the cell.
Species in the genus Oxybelus
are somewhat small wasps that make their burrows in sandy places and
provision the cells with flies. Oxybelus quadrinotatus Say carries prey in an inverted position beneath
the body, the head grasped by the hind pair of legs in such a position that
the entire abdomen projects caudad beyond her body (Peckhams 1898). Flies are killed at capture. In other species death ensues when the
thorax is crushed with the mandibles. Peckhams (1898) studying Hypocrabro
stirpicola Pack., noted that
activity continued during nighttime.
The flies used in provisioning the nest were in the Calliphoridae and
Anthomyiidae, being dead at the time of storage. Xestocrabro sayi Ckll. (= sexmaculata S. & F.) does not harm its prey, because when cells
are opened the flies and gnats are active, some being able to escape. Crabro
brevis Lind. stores its nests with
adult chrysomelid beetles in the Halticinae (Grandi 1925). Those found in a cell may represent
several species or even genera, and in different localities the wasp may
specialize on different species. The
nest comprises 6-10 cells, each of which is provisioned with 12-25
beetles. Some species of the genus
have been known to carry prey impaled on the sting. In Europe, Ceratocolus
alatus Panz., stores its nests with
adult moths of Phlyctaenodes sticticalis L., and the cocoons are
made largely of the prey's wings, the habit of using remains of prey in the
cocoon being common to many species. Tracheloides hicksi Sandh. has been found to attack ant columns on tree
trunks, the female parasitoid seizing an ant and flying away with it to a
nearby branch, where it is stung. This group was reported as a subfamily of Crabronidae in the
Apoidea by Finnamore & Michener (1993).
They are cosmopolitan with over 1,302 species known as of 2000. They are rather uniform in color, size and
shape. Adults are generally black or
black with yellow or white markings.
They stock their nests with Diptera.
In North America there are around 200 species in 14 genera (Finnamore
& Michener 1993). Further
Description
The subfamilly Crabroninae is the most diverse group in the wasp
family Crabronidae, containing over 100 genera. The subfamily consists of
solitary, predatory wasps. The adult females of many groups dig tunnels in
the ground for nesting, but others use different techniques, including the
construction of tube-like mud nests (e.g., Trypoxylon politum). As with all other
sphecoid wasps, the larvae are carnivorous; females hunt for prey on which to
lay their eggs, supplying the larvae with paralyzed, living prey when they
emerge. A key reference is Bohart & Menke (1976). References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] |