Ichneumonid Parasite Research Articles

ESTABLISHMENT IN MAINE, NOVA SCOTIA, AND NEW BRUNSWICK OF OLESICAMPE BENEFACTOR (HYMENOPTERA: ICHNEUMONIDAE), AN INTRODUCED ICHNEUMONID PARASITE OF THE LARCH SAWFLY, PRISTIPHORA ERICHSONII (HYMENOPTERA: TENTHREDINIDAE)

AbstractSmall numbers (147–388) of Olesicampe benefactor Hinz, a European ichneumonid parasite of the larch sawfly, Pristiphora erichsonii (Htg.), were released in Maine, Nova Scotia, and New Brunswick in 1967. The parasite became established and has survived through two winters at five release points, and three winters on three release sites; on two sites the continued survival of the parasites is unconfirmed because of the collapse of the host population. O. benefactor is known to disperse slowly and even if it is successful in controlling the sawfly in the release areas, control over large areas may require releases at many locations.The subject of the range of host densities at which parasite releases should be made to ensure the greatest parasite production per parasite released, and hence the greatest chance of successful establishment, is discussed.

The immature stages of European Ichneumonid parasites of Siricine Woodwasps

SYNOPSIS The immature stages of Rhyssa persuasoria, R. amoena, Megarhyssa emarginatoria, Pseudorhyssa sternata and Odontocolon geniculatus, ichneumonid ectoparasites of European Siricidae, are described and a key based on the last larval instars of these species is included. Their relationships are discussed with reference to the morphology of the intermediate and final instars.

The immature stages of European ichneumonid parasites of siricine woodwasps

SYNOPSISThe immature stages of Rhyssa persuasoria, R. amoena, Megarhyssa emarginatoria, Pseudorhyssa sternata and Odontocolon geniculatus, ichneumonid ectoparasites of European Siricidae, are described and a key based on the last larval instars of these species is included. Their relationships are discussed with reference to the morphology of the intermediate and final instars.

Host finding by Rhyssa persuasoria (L.), an ichneumonid parasite of siricid woodwasps

1. 1. Exploratory behaviour over the bark of infested timber comprises a survey of the surface with the antennae, sustained antennal activity (palpating) in areas of special interest, and ovipositor probing to a depth of 1 to 3 mm into the wood. 2. 2. Drilling to a depth of more than 5 mm is elicited by stimuli emanating from within the timber, with surface features such as cracks in bark and wood, influencing the point of ovipositor insertion. Siricid oviposition punctures do not attract the parasite or stimulate drilling. 3. 3. Antagonistic behaviour between females results in the acquisition of loosely defined territories. 4. 4. The majority of drills are made in response to siricid tunnels and are not random, but the parasite does not apparently follow concentration gradients along individual tunnels. 5. 5. Females are able to detect and parasitize dead hosts in logs, demonstrating that sound is not a necessary stimulus for drilling, and is not essential for host detection. 6. 6. The majority of drills are elicited by siricid frass; washed siricid larvae alone stimulate no host-searching response. The frass nearest the host is most attractive, and the attraction of the frass decreases with increase in distance from the host. Wet frass elicits more drilling than dry frass. 7. 7. Cultured fungal symbionts 3 to 4 months old are the most attractive, coinciding with maturation of host larvae in timber under similar conditions. There is no evidence that the species of tree influences attraction, or of pre-imaginal conditioning of the parasite to its host's symbiont. Comparison of the symbiont with several common woodland fungi demonstrated the specific attractiveness of the symbiont. 8. 8. Comparison of named Stereum and Amylostereum species with the symbionts demonstrated a marked preference for the S. juvencus symbiont which is probably closely related to Amylostereum species. 9. 9. Aqueous and ethanolic extracts of frass and fungus stimulate drilling. 10. 10. When siricid larvae are maintained on frass or fungus medium, or when siricid larvalgut extract, and chitinase are incorporated into the medium, the attractiveness of the substrate is increased.

Host Records for the Parasites Diadegma acuta and Rhexidermus huardi (Hymenoptera: Ichneumonidae)

New host records were obtained for 2 ichneumonid parasites of Platyptila pica cratea Fletcher. The biology of this insect was reported by Lange (1950.)

LASPEYRESIA PSEUDOTSUGAE N. SP. (LEPIDOPTERA: OLETHREUTIDAE), A BARK MINER IN DOUGLAS-FIR

AbstractA 5-year study of Laspeyresia pseudotsugae n. sp. (Lepidoptera: Olethreutidae) yielded considerable data on the habits, life history and immature stages of this insect, which gained attention because of its conspicuous bark-mine scars on the trunks of young Douglas-fir trees, Pseudotsuga menziesii (Mirbel) Franco. The mines are not deep enough to cause serious damage. L. pseudotsugae has a 1-year life-cycle. Three species of ichneumonid parasites were recovered, and several predators were identified.

Host Records for the Parasites Diadegma acuta and Rhexidermus huardi (Hymenoptera: Ichneumonidae)

New host records were obtained for 2 ichneumonid parasites of Platyptila pica cratea Fletcher. The biology of this insect was reported by Lange (1950).

A New Synetaeris Parasite of the Spruce Budworm in Canada (Hymenoptera: Ichneumonidae)

The following description is offered for a previously undescribed ichneumonid parasite of Choristoneura fumiferana (Clem.) reared, in recent years, in several parts of Canada, by officers of the Forest Entomology and Pathology Branch, Department of Forestry.

The Effect of Multiparasitism on Populations of Two Parasites and Their Host

In an experimental study of multiparasitism attention has been paid primarily to its effects on individual hosts and to the determination of the factors which control the result of competition. It has been established that the time of oviposition is of prime importance, but that the rate of preimaginal development, which in turn is dependent upon the species of host attacked and the environmental temperature, is an important modifying factor (Fisher 1959, 1961b). The ichneumonid parasites used in this study were Horogenes chrysostictos Gmelin and Nemeritis (Idechthis) canescens Grav. Both are natural parasites of larvae of the moth Ephestia sericariumi Scott (= E. kulhniella Zeller) (Lepidoptera: Phycitidae). On simultaneous oviposition in this host by both parasite species Horogenes wins in competition because the duration of its egg stage is shorter than that of its opponent, Neweritis and it is thus able to attack the latter with the well developed mandibles of the first instar larva. But since simultaneous oviposition is unlikely to occur in the field and the difference in the duration of egg development in Ephestia is relatively small (10 ? 2 hr at 250C), for practical purposes neither species has an intrinsic advantage and the result of multiparasitism is determined by the time of oviposition. Any extrinsic superiority (sensu Smith 1929) of either species therefore depends upon the fecundity and maximum population density attained by each. Although the fecundity of the 2 species is approximately the same (Fisher 1959), the potential capacity for increase is very much greater for Aremeritis since it is a wholly parthenogenetic species. In consequence this parasite has an additional intrinsic advantage over Horrogeucs which, in natural populations, should far outweigh any superiority which the latter could show in multiparasitism. Since Flanders (1948) has shown that populations of Ephestia and Nemeritis can exist indefinitely on a continuously available source of food for the host, it seemed possible to set up experimental ecosystems consisting of Ephestia, Nemeritis and Horogenes to study the effect of multiparasitism on the population densities of all 3 species. The method used was adapted from that described by Flanders (1958). Each ecosystem consisted of a rectangular w-ood cage of internal dimensions 16 X 16 X 10 inches, with nylon gauze side panels, a glass top and a wooden floor. The floor was divided into 25 squares, each of about 10 sq. inches in area. The basis food of Ephestia, equal parts of sterilized rolled oats and whole wheat flour, was contained in 10 g lots in small waxed paper cups. One cup of food was added each week to a square selected at random until all the squares were filled. On the 26th week the first cup, then exhausted of food, was replaced by a newly filled one and the continuation of this procedure ensured constantly enduring host populations with larvae at every stage of development.

The Relative Effects of Cocoon Submergence on the Mortality of the Larch Sawfly, Pristiphora Erichsonii (Hymenoptera: Tenthredinidae), and Its Parasite Bessa Harveyi (Diptera: Tachinidae)1

Laboratory experiments on effects of submergence of larch sawfly cocoons, immediately after the overwintering period, confirmed earlier reports on the resistance of the eonymphal stage to flooding. An ichneumonid parasite, Mesoleius tenthredinis Morley, appeared able to survive flooding as well as the host, but the tachinid Bessa harveyi (Tnsd.) was found susceptible even when the flooding was of short duration. The early inception of growth and the rapid development of B. harveyi maggots, and the resultant active metabolism, seemed to account for its susceptibility to submersion. Sawfly larvae parasitized by this fly were found to have a higher rate of oxygen consumption than unparasitized larvae. Susceptibility to submersion seems to be a factor limiting the effectiveness of B. harveyi , and may account for its reported sporadic distribution in localized areas.

Experimental studies in insect parasitism. XI. The haemocytic reaction of a caterpillar under varied conditions.

Eggs or young larvae of an ichneumonid parasite, Nemeritis , injected into caterpillars of the tomato moth, Diataraxia , evoked a rapid reaction of the haemocytes, which led to the encapsulation of the parasite within 4 h. The further development of the capsule is described, and evidence is adduced that the encapsulated parasites were killed by asphyxiation. Encapsulation was blocked by injection of carbon particles, but only when the doses were so large that they affected the general health of the hosts; it was temporarily less intense in superparasitized hosts; and it appeared to be slightly depressed by cortisone. Attempts to induce tolerance in the host by various methods—by repeated parasitization, by inoculation with an homogenate of parasite larvae, by inoculation with the blood of a susceptible host and by embryonic inoculation of substances from an homogenate of parasite larvae—all failed to protect the parasite, which was encapsulated as thickly and rapidly as in untreated caterpillars. When the parasite was given prior experience of Diataraxia blood by two different methods it acquired no immunity. The haemocytic reaction was similarly evoked by other species of parasites, by dead parasites, by glass rods and pieces of nylon thread, by injured tissues of the caterpillar itself, and by organs transplanted from caterpillars of another species. Organs transplanted from other caterpillars of the same species attracted haemocytes only to injured surfaces. Haemocytic capsules formed in one caterpillar of Diataraxia and transplanted to another caterpillar of the same species were accepted as intraspecific implants and aroused no reaction; capsules formed in another species and transplanted to Diataraxia evoked a strong haemocytic reaction in the second host. It is concluded that surface properties of the parasite or implant determine whether or not it shall be encapsulated.

Scambus pterophori (Ashm.) (Hymenoptera: Ichneumonidae), a New Parasite of the European Corn Borer, Pyrausta nubilalis (Hbn.) (Lepidoptera: Pyralidae), in Canada

In late August, 1957, a parasitized second-generation pupa of Pyrausta nubilalis (Hbn.) was observed in silks of an immature corn ear in the experimental plots at St. Jean. The pupa was incubated at 75°F. in a petri dish, and two weeks later an ichneumonid parasite emerged and was identified by Mr. G. S. Walley, Entomology Division, Ottawa, as Scambus pterophori (Ashm.). Asecond generation of P. nubilalis is very unusual in the St. Jean area. This is apparently the first record of this ichneumonid as a parasite of P. nubilalis in Canada.

Trimorphism in the Ichneumonid Parasite Geliscorruptor

ABSTRACT The ichneumonid parasite Gelis corruptor is trimorphic in the development of wings: females are invariably apterous; males may be either macropterous or micro-pterous. Females show no trace of wing-buds in the pupa and are without wing-disks in the late larval stage. The female apteryis a sex-limited character and is of genetic origin. All male larvae have wing-disks and are potentially fully winged males. On a host providing adequate nourishment, the male larva develops into the macropterous form; on a host providing meagre nourishment, it develops into the micropterous form. Eggs or young larvae transferred from a small to a large host develop into macropterous males ; larvae removed from large hosts before they have finished feeding develop into micropterous males. The dimorphism of the male sex is therefore controlled by the host viewed as a quantity of food. The two forms of males differ not only in the development of the wings but also in the structure of the thorax, the size of the ocelli, the form of the endoskeleton, and the development, innervation, and tracheal supply of the thoracic muscles. The trimorphism is strict, since all females are apterous and (with the exception of one abnormal specimen) all the males examined belong without intermediates to either the macropterous or the micropterous form. The principal differences observed between the three forms all appear to be bound up with the condition of the wings. How the development of this complex of characters is organized, particularly in the two forms of males, presents an interesting problem of morphogenesis.

On the Identity of an Ichneumonid Parasite of Hepialus lupulinus (L.)

A paper by the present writer on an Ichneumonid parasite of Hepialus lupulinus (L.) under the name Alomya debellator (F.) appeared in the last issue of this journal (1950). It now transpires that this Ichneumonid is not A. debellator but Ichneumon suspiciosus Wesm. This error was pointed out, as soon as the paper was published, by Mr. J. F. Perkins of the British Museum, and agreed by Mr. G. J. Kerrich of the Commonwealth Institute of Entomology, both of whom, as specialists in the Ichneumonidae, recognised the illustration produced from a drawing prepared by Mr. A. J. E. Terzi as representing a species of Ichneumon, probably I. suspiciosus. The actual specimen illustrated has been traced, and its identification has been confirmed by Mr. Perkins as Ichneumon suspiciosus Wesm. It is certain, moreover, that all the parasite material involved was this species and not A. debellator.

The Biology and economic Importance of Alomya debellator (F.), a remarkable Parasite of the Swift Moth, Hepialus lupulinus (L.)

While investigating the biological control of certain Hepialids, a very interesting Ichneumonid parasite, Alomya debellator (F.) was reared from the pupae of the Swift Moth, Hepialus lupulinus (L.).The systematic position of this parasite has been thoroughly investigated and the members of the special sub-family, Metopiinae, to which it has been assigned, are characterised by the possession of only one trochanter on each foreleg. A. debellator is the sole representative of the tribe Alomyini.After extensive collecting, and a thorough search of the literature, the conclusion has been reached that the distribution of this parasite is fairly local, but its range in Great Britain and certain other European countries is wide. As a result of the present study H. lupulinus has been definitely proved to be the host of A. debellator.A fairly full account of the life-history of the parasite has been worked out, and amongst other things, a point of special interest is the arrest in development which occurs in the first-instar larva. Possible explanations of this phenomenon are discussed.The morphological and anatomical structure of the larva have been fully investigated and described, and useful diagnostic characteristics both for the primary and mature larval stages, have been discovered.The paper concludes with a discussion on the potential value of A. debellator as a factor in the control of H. lupulinus, and other allied species belonging to the genus Oncopera in Australia. It is maintained, on the evidence collected, that this parasite in some areas is probably the most important single factor of biological control. A note on the feeding habits of Hepialids, and a few remarks about the collecting of parasitised material are appended. Altogether some 7,000 specimens of H. lupulinus larvae and pupae many of which were parasitised by A. debellator were collected from the Willingham area of Cambridgeshire.