The Ichneumen Fly Epiurus pterophori Ashmead.
Psyche 34(6):227-229, 1927.
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19271 The Ichneumon Fly, Epium pterophori Ashmead 227 OBSERVATIONS ON THE ,ICHNEUMON-FLY EPI URUS PTEROPHORI ASHMEAD.
BY MAGEL C. WILDER.
Cornell University, Ithaca, N. Y
The stalks of the evening primrose (Oenothera lamarckiana) are very commonly found infested with larvae of the moth, Lophopiilus eloisella. These larvae are borers in the pith cavity of the stalks.
They hibernate in the stalks. In autumn each larva prepares itself a hibernation chamber in the stalk by setting off a section of the empty pith cavity by building two partitions of frass and silk a little further apart than the length of its own body, and by lining the chamber so formed with a thin trans- parent film of silk. On splitting apart the pith cavities in autumn a number of such chambers may often be found in a single stem. But in some of these chambers, instead of the yellow moth larva there is found the whitish -larva of a rather large hymenopterous parasite. The rearing of this parasite was undertaken at the suggestion of Professor James G. Needham and continued under his kindly direction. It proved to be the larva of the ichneumon fly, Epiurus pterophori The evening primrose grows wild in vacant lots, and was gathered in a number of places at Ithaca, N. Y. The stalks were first brought into the laboratory and examined on March 13th. The moth larvae were found distributed throughout the stalks, occurring very frequently. The larvae of Epiurus pterophori were found to occur, seldom more than one in a stalk in a very small percentage of the stalks examined. Primrose stalks collected from certain places contained none. It is always found within a hibernation chamber but in no particular region of the stalk, and the head capsule together with other skin fragments of Lophop- tilus have been found with it. This indicates the parasitic nature of Epiurus pterophori.
The larva is yellowish-white, flattened dorso-ventrally, and reposes normally in its cell in a curved position. The larvae measure from six to seven millimeters in length and are about one millimeter in breadth. Four narrow chitinized plates are
Larva were found in stalks collected and examined through- out March and April.
The first pupa was found within the
stalk Mafeh 22nd from material which had been inside the laboratory for a week. Pup were found to exhibit a great deal of activity; some were able to turn their bodies completely over within the cell.
The first adult was found March 29th in a stalk that had previously been slit open to show the larvae. The insect was
19271 The Ichneumon Fly, Epiurus ptero phori Ashmead 229 left within the cell in which it was found, the upper surface of the stalk replaced, and both fastened securely together. This section of the stalk was kept under observation in a cheese-cloth covered battery jar. The adult emerged through a small round hole it had made in the stalk a few days afterward. The adult was identified by Dr.
J. Chester Bradley as
Epiurus pterophori Ashmead. It is known also in literature as Pimpla pterelas, Pimpla pterophori Ashmead, and Scambus ptere- Zas.
Notes kindly given by Dr. Bradley indicate that it is ^'parasitic on larvae of stem-boring and stem-gall-making Lep- idoptera and Coleoptera such as Gelechia galloe-solidaginis, G, gdloe-asterella, Pyronata nubilalis, and Stagmatoph,ora ceanothiella. In literature it is also recorded as a parasite of G. galloe-asterella, and the beetle Mononychus vulpec~lus.~'
A description of the adult may be found in Walsh. Epiurus pterophori has been mentioned as having been found feeding on the pupa of the European corn-borer.3 Ac- cording to the description: "the hymenopterous larva of Epiurus pterophori was found feeding on the internal juices of a P. nu- bilalis pupa which had been broken open. The full-grown
parasite larva spun a brown silken cocoon and pupated within the remains of its host. Only two of these parasites were bred." Although a pale silken web was found to be spun by the parasite, it was not such that could be described as a "brown silken cocoon" as is described above.
By the first of June all of the adults had emerged. The
adults were transferred to breeding cages containing evening primrose plants. Although an attempt at oviposition was noted on the part of one female against the glass wall of the battery jar, none was observed after they were placed with the evening prim- rose plants. No mating was observed; and no feeding, although several sorts of food were offered, first sugar and water solution, and later small insects, placed in the cages. The adults lived for
but a few days, during which time they were moderately active. Literature Cited.
J. Hamilton: Ent. News. 1894-'95, pp. 287-288. (2)
Walsh: Trans. Acad. Sci. of St. Louis 111, 1873, pp. 1, 133. (3)
Mass. Ex. Sta. Bull. 189, p. 58, 1919.
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