154
V. G. DETHIER
While the behavior of Trichogramma
was being investigated, Ullyett
(1936) was challenging the statements of Thompson and Parker (1927)
with experiments on the partially monophagous wasp
Microplectron
fuscipennis Zett, which parasitizes last-stage larvae (in cocoons) of
sawflies of the genus Diprion. The wasp is attracted by odor to its host
from a distance of 5 to 6 mm. As soon as the host is found, it is subjected
to antennal exploration. At this point shape as well as size is of critical
importance. Larger objects are invariably preferred. If the host is
healthy and movement is apparent, the host is accepted and eggs laid.
The third parasite which has been subjected to extensive experimental
analysis is the chalcid wasp Mormoniella vitripennis (Walker), which
parasitizes the pupae of muscoid flies. The wasp is attracted to the
general area of the host by the odor arising from the action of fly larvae
on meat (Jacobi, 1939). Fresh meat or meat acted upon by bacteria
is unattractive (Edwards, 1954). The behavior pattern which now
follows has been described in detail and investigated carefully by Jacobi
(1939) and by Edwards (1954). Odor from the host area induces in
the parasite a wandering typified by repeated twistings and turnings.
When a short distance away—ca. 15 mm. (Jacobi), 2-3 mm. (Edwards)
—the parasite notices the puparium. According to Jacobi the stimulus is
the odor of the puparium itself. Edwards has demonstrated, however,
that wasps not only are stimulated visually by small objects close at
hand but will investigate them. Laing found that Trichogramma similarly
employed vision at this point in the proceedings. Since hosts can be
located in the dark by both wasps, the possibility cannot be dismissed
that some other sense substitutes in the absence of vision.
Having discovered the puparium the wasp turns, walks directly toward
it, subjects it to an antennal examination, then climbs upon it. Once on
top the wasp subjects the entire exposed surface to a complete examination with the antennae. The examination is carried out by rapidly striking the antennae repeatedly against the surface ("drumming" of Edwards, "Trommelreaktion" of Jacobi). Upon completion of this action
the parasite stops, flexes the body, and sometimes commences tapping
the puparium with the tip of the abdomen. Little movements of the feet
frequently occur simultaneously. The next action is drilling by the ovipositor. If the host is suitable, eggs are laid, a feeding tube is formed
at the wound, presumably from secretions of the wasp's colleterial glands,
and the wasp sucks the host's blood for a period of 3 to 5 minutes. If
the puparium is unsuitable for oviposition, no eggs are laid. In either
case, the pattern is well defined, and at certain points releasing stimuli
are received. These points are: first contact with the puparium, drumming, drilling, insertion. According to Jacobi drumming is released by
V. G. DETHIER
While the behavior of Trichogramma
was being investigated, Ullyett
(1936) was challenging the statements of Thompson and Parker (1927)
with experiments on the partially monophagous wasp
Microplectron
fuscipennis Zett, which parasitizes last-stage larvae (in cocoons) of
sawflies of the genus Diprion. The wasp is attracted by odor to its host
from a distance of 5 to 6 mm. As soon as the host is found, it is subjected
to antennal exploration. At this point shape as well as size is of critical
importance. Larger objects are invariably preferred. If the host is
healthy and movement is apparent, the host is accepted and eggs laid.
The third parasite which has been subjected to extensive experimental
analysis is the chalcid wasp Mormoniella vitripennis (Walker), which
parasitizes the pupae of muscoid flies. The wasp is attracted to the
general area of the host by the odor arising from the action of fly larvae
on meat (Jacobi, 1939). Fresh meat or meat acted upon by bacteria
is unattractive (Edwards, 1954). The behavior pattern which now
follows has been described in detail and investigated carefully by Jacobi
(1939) and by Edwards (1954). Odor from the host area induces in
the parasite a wandering typified by repeated twistings and turnings.
When a short distance away—ca. 15 mm. (Jacobi), 2-3 mm. (Edwards)
—the parasite notices the puparium. According to Jacobi the stimulus is
the odor of the puparium itself. Edwards has demonstrated, however,
that wasps not only are stimulated visually by small objects close at
hand but will investigate them. Laing found that Trichogramma similarly
employed vision at this point in the proceedings. Since hosts can be
located in the dark by both wasps, the possibility cannot be dismissed
that some other sense substitutes in the absence of vision.
Having discovered the puparium the wasp turns, walks directly toward
it, subjects it to an antennal examination, then climbs upon it. Once on
top the wasp subjects the entire exposed surface to a complete examination with the antennae. The examination is carried out by rapidly striking the antennae repeatedly against the surface ("drumming" of Edwards, "Trommelreaktion" of Jacobi). Upon completion of this action
the parasite stops, flexes the body, and sometimes commences tapping
the puparium with the tip of the abdomen. Little movements of the feet
frequently occur simultaneously. The next action is drilling by the ovipositor. If the host is suitable, eggs are laid, a feeding tube is formed
at the wound, presumably from secretions of the wasp's colleterial glands,
and the wasp sucks the host's blood for a period of 3 to 5 minutes. If
the puparium is unsuitable for oviposition, no eggs are laid. In either
case, the pattern is well defined, and at certain points releasing stimuli
are received. These points are: first contact with the puparium, drumming, drilling, insertion. According to Jacobi drumming is released by