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1. Itoplectis conquisitor (Say, 1835) (Figs 5, 6) Cryptus conquisitor Say 1835: 232 [holotype ♀ (USNM), USA, Indiana (destroyed, see Townes & Townes 1966: 22)]., Published as part of Khalaim, Andrey I. & Ruíz-Cancino, Enrique, 2021, Darwin wasps of the subfamily Pimplinae (Hymenoptera: Ichneumonidae) of Mexico: genera Apechthis Förster, Itoplectis Förster and Pimpla Fabricius, pp. 451-491 in Zootaxa 5071 (4) on page 456, DOI: 10.11646/zootaxa.5071.4.1, http://zenodo.org/record/5726393, {"references":["Say, T. (1835) Descriptions of new species of North American Hymenoptera, and observations on some already described. Boston Journal of Natural History, 1 (3), 209 - 305.","Townes, H. K. & Townes, M. (1966) A catalogue and reclassification of the Neotropic Ichneumonidae. Memoirs of the American Entomological Institute, 8, 1 - 367."]}

Elongate placoid sensilla similar to those in the braconid, Coeloides brunneri , occur on all segments of the antennal flagellum of both sexes of the ichneumonid, Itoplectis conquisitor . They run parallel to the long axis of the antenna, are distributed around the entire circumference of the segment, and range from 9–40% of the length of the segment. Scanning electron microscopy discloses externally a deep groove around the periphery of the sensillum, and internally, a large aperture in the cuticular floor, shallow lamellae, and intertwining ridges on the ceiling of the dome of the median channel. In transmission electron micrographs, typical sensory neurons can be seen, with characteristic nerve cell bodies, ascending dendritic processes, basal bodies and ciliary regions. Many dendritic branches pass along the 2.1 μ wide median channel just underneath the 0.02–0.03 μ thick dome.

A laboratory investigation of theItoplectis conquisitor sex pheromone was initiated to elucidate the structure(s) of the active component(s) of the system. Functional group tests performed on crude virgin female extract classified the pheromone as unsaturated aldehyde(s) and/or ketone(s). Isolation of active fractions by gas-liquid chromatography (GLC) suggested the existence of a multicomponent pheromone system. Analysis by gas chromatography-mass spectrometry indicated the presence of saturated and unsaturated aldehydes including neral and geranial. When mixtures of neral and geranial were bioassayed independently and in combination with other active GLC fractions, they elicited male sexual activity of intensity comparable to that released by the GLC fraction (DEGS E) from which they were isolated. The authors conclude that neral and/or geranial are components of the sex pheromone system of this species.

Parasitism of Archips semiferanus (Walker) larvae in Pennsylvania became appreciable in early June (18.0–63.1%), which coincides with the appearance of 5th instars. Dipteran parasitism of the larvae is major (16.9–57.7%), while hymenopteran parasitism is minor (1.1–5.4%). Conversely, dipteran parasitism of the pupae is minor (0.72–2.6%) and hymenopteran parasitism is major (3.5–32.3%). Twenty-two parasites have been recovered from larvae and pupae samples, 16 of which are new host records. The major larval parasite is Lypha setifacies (West) and the major pupal parasite is Itoplectis conquisitor (Say).

Four indigenous parasites of R. buoliana are discussed: Exeristes comstockii (Cress.), Scambus hispae (Harr.), Scambus tecumseh Vier. and Itoplectis conquisitor (Say). The first three are external larval parasites and the fourth an internal pupal parasite. Observations are given on the hosts, life histories, and habits under laboratory conditions. The immature stages are described.

A chemically defined, synthetic medium that induces oviposition in the parasiteItoplectis conquisitor(Say) has been developed. The medium contains serine (0.5M), arginine (0.05M), leucine (0.065M), and magnesium chloride (0.025M); and it is more effective than host haemolymph in inducing oviposition. This completely artificial oviposition stimulant was developed to facilitate the mass rearing of the parasite on an artificial diet.

Females of I. conquisitor could not be conditioned to attack horizontal tubes instead of vertical tubes of the same size and probably cannot distinguish between them. I. conquisitor could be conditioned to attack tubes of particular lengths or diameters and tubes mounted on pins rather than on plastic forms. These results are interpreted as showing that the parasites can recognize these differences in the host shelter and that these characteristics could influence host selection. It is suggested that if a polyphagous parasite to be introduced against a particular pest is first conditioned to that host in pieces of its host plant, the success of the parasite in finding that host and hence its chances of establishment would be increased.

A physiologically active fraction inducing oviposition inItoplectis conquisitor(Say), and isolated from the hemolymph of some insects, was studied in detail using hemolymph fromGalleria mellonella(L.) andCelerio euphorbiae(L.). The active fraction consisted of hexoses and some 19 common amino acids. The hexose component may act as a synergist in inducing oviposition while not all amino acids were necessary to induce oviposition.I.conquisitorlaid eggs in the hemolymph of species of Lepidoptera, Hymenoptera, Coleoptera, and Trichoptera, but did not oviposit in the hemolymph of species belonging to Hemiptera, Orthoptera, Neuroptera, Plecoptera, and Crustacea.

Females of Nemeritis canescens (Grav.) were conditioned to associate the odour of geraniol with the presence of hosts. Females conditioned for 10 days retained the conditioned response for 6 days. Associative learning in N. canescens, an oligophagous parasite, is less strong than in Itoplectis conquisitor (Say), a polyphagous parasite. This finding may reveal a general difference between oligophagous and polyphagous parasites.

Twenty species of parasites and associated insects were reared from shoots of red pine, Pinus resinosa Ait., infested with the European pine shoot moth, Rhyacionia buoliana (Schiffermuller), at Oakland, Md. In trees 7 ft tall, Hyssopus thymus Girault was more abundant than Exeristes comstockii Cresson, but the reverse was true in trees half that height. Total parasitism and parasitism by H. thymus and Eurytoma pini Bugbee were greater in the lowest ⅓ than in the topmost ⅓ of the tree; E. comstockii and associated insects of uncertain status—lepidopterans, coleopterans, and the dipteran Oscinella conicola (Green)—were most abundant in the topmost ⅓. Of Itoplectis conquisitor (Say) only males were reared. Usually only 1 shoot moth larva was found per shoot, but occasionally there were as many as 5; more than 1 larva per shoot occurred more often in the topmost than in the lowest ⅓ of the trees. Trees 3½ ft tall had a higher infestation rate than those 7 ft tall. Lammas shoots were infested at the same rate as normal shoots. In 3½-ft trees, 23% of the shoots were in the lowest ⅓ and 24% in the topmost ⅓ of the tree; in 7-ft trees, 50% and 10%, respectively.

Females of I. conquisitor were conditioned to associate colour with the presence of hosts. Conditioning was important only during searching and did not affect the distribution of attacks once hosts were found. The ability of this species to associate colour with the presence of hosts could increase its efficiency as a parasite. Females of I. conquisitor showed an innate preference for blue over yellow.

A sensillum in the shape of a truncate cylindrical peg is present on the apex of the antenna in both sexes of Itoplectis conquisitor (Say). The sensilla occur in distinct fields of 19 to 38 pegs per antenna in males , and 26 to 35 pegs per antenna in females (x = 30.6). The pegs measure 1 to 15 μ, in height in males and 4 to 13 μ in females, and 2 to 6 μ in diameter in males and 2 to 5 μ in females. Pegs in the inside ranks at the very tip of the antenna are shorter than those in outside ranks which are more subterminal in position. This height variation results in the flat to slightly concave tips of the pegs being aligned on approximately the same plane. Innervation was confirmed by light microscope observations of sectioned material. The placement of the pegs at the antennal apex suggests that they perceive stimuli in the act of antennal tapping.

The effects of fiood od the fecundity and longevity of the adults of hymenopterous parasites vary remarkably, not only between species that are host feeders and those that are not host feeders, but also within these groups. It is known, for example, that the females of Itoplectis conquisitor (Say) develop only few eggs without feeding on body fluids of their host. In the present investigations it is shown that the females of Scambus buolianae (Htg.) are not able to deposit any eggs without first feeding on the tissues of their host. Such information is important for the successful establishment of newly-imported parasites.

This note reports the first in vitro oviposition and rearing of a parasitic insect, the endoparasitoid wasp Itoplectis conquisitor (Say), a male, on an artificial host consisting of an encapsulated synthetic, or meridic (Dougherty 1959, p. 53), medium.Parasitic insects, of course, have been reared in vitro on meridic diets (House 1954; Yazgan 1972; Thompson 1975). Some were reported to oviposit into artificial objects (Arthur et al. 1972; Rajendram and Hagen 1974; Hoffman et al. 1975). Trichogramma pretiosum Riley laid viable eggs and development to adults occurred in small wax-resin spheres filled with host haemolymph (Hoffman et al. 1975).

A 4-year study of the naturally occurring biotic control factors affecting the eye-spotted bud moth, Spilonota ocellana (Denis and Schiffermuller), on apple in Wisconsin revealed the existence of parasitic, predatory, and microorganismal agents. Nine hymenopterous parasites, three predators, and four pathogens were involved. Principal parasitic species were Itoplectis conquisitor (Say) and Habrocytus phycidis Ashmead. Aspergillus flavus Link and a polyhedral virus were the most prevalent causes of disease. A high mortality occurring in the pupal stage could not be attributed to known causes. It is postulated that the comparatively low numbers of primary species and their small part in the regulation of the eye-spotted bud moth population may have been due mainly to the extensive use of pesticides in the area. The need for the use of selective pesticides in an integrated control program is emphasized.

In mid-July 1969, an extremely heavy population of the yellow-collared scape-moth, Cisseps fulvicollis (Hübner), was observed in a 45-acre field of grain corn at Napierville, Que. Larval feeding was heavily concentrated on the lower leaves of the plants, leaving only the mid-rib of the leaves unattacked. Approximately 92% of the pupae were parasitized by Itoplectis conquisitor (Say) and Ichneumon sp. of the group winkleyi, thereby reducing the moth population quite substantially. From samples of ears taken at harvest in the unattacked and infested portions of the field, the reduced yield was evaluated at about 7%.This is apparently the first published record of this amatid moth as an economic injurious insect on grain corn in Canada.

An unique development in insect dietetics is announced, namely, the rearing of an hymenopteran — Itoplectis conquisitor (Say), an ichneumonid endoparasitoid of other insects — axenically on a chemically-defined synthetic diet. First heuristic attempts produced a yield of about 17% adults.

When the polyphagous parasite Itoplectis conquisitor (Say) was reared on either of two hosts, Thymelicus lineola (Ochs.) or Galleria mellonella L., it showed no preference for the host from which it had emerged when exposed to equal numbers of the two hosts in the same type of ecological niche. No evidence for the existence of preimaginal conditioning in I. conquisitor was obtained.

The capture of Itoplectis conquisitor (Say) is being reported as the first record of this ichneumonid as a parasite of the European corn borer Ostrinia nubilalis (Hübner) in Canada.

Development of artificial hosts for mass production of parasites is currently of considerable interest in biological control. Creation of a suitable artificial host will require not only provision of all nutritional requisites but also incorporation of factors required to release oviposition. Arthur et al. (1969) isolated a factor from the hemolymph of host insects which induced oviposition by Itoplectis conquisitor (Say) into artificial hosts, but they had to condition the parasites to probe these host facsimiles before the effect of test substances could be assessed.