The remarkable biology of a new species of Gelis Thunberg, 1827 (Ichneumonidae, Phygadeuontinae), a solitary endoparasitoid of fresh eggs of Timarcha (Coleoptera, Chrysomelidae)

A new species, Gelis timarchae Schwarz, Shaw & Kan, is figured and described from specimens reared as a solitary endoparasitoid of fresh eggs of Timarcha nicaeensis in the south of France. Oviposition behaviour of the adult parasitoid, directly into the host cytoplasm, is described and links to videos are given. This appears to be the first record of any ichneumonid developing as an endoparasitoid of an insect egg, and it is a major departure from hitherto known ectoparasitoid (or spiders’ egg-predation) behaviour in the genus Gelis. Fluid from the host egg issuing from the base of the parasitoid’s ovipositor early in the oviposition process is interpreted as a necessary reduction of hydrostatic pressure before the parasitoid egg can be forced down the ovipositor. The egg and first instar larva are figured; the latter is caudate, with the caudal appendage very unusual in being bifurcate. The complex phenology and diapause of the parasitoid were investigated partly experimentally; it is broadly bivoltine with a prepupal diapause in summer, but extra generations and prolonged diapause were both also seen.

Generalized conditions for coexistence of competing parasitoids on a shared host

Motivated by the univoltine life histories of insects residing in the temperate-regions of the world, there is a rich tradition of modeling arthropod host-parasitoid interactions using a discrete-time formalism. We introduce a general class of discrete-time models for capturing the population dynamics of two competing parasitoid species that attack the same vulnerable stage of the host species. These models are characterized by two density-dependent functions: an escape response defined by the fraction of hosts escaping parasitism; and a competition response defined by the fraction of parasitized hosts that develop into adult parasitoids of either species. Model analysis reveals remarkably simple stability conditions for the coexistence of competing parasitoids. More specifically, coexistence occurs, if and only if, the adult host density increases with host reproduction rate, and the log sensitivity of the competition response is less than half. The latter condition implies that any increase in the adult parasitoid density will result in a sufficiently slow increase in the fraction of parasitized hosts that develop into parasitoids of that type. We next consider a model motivated by differences in parasitism risk among individual hosts with risk from the two parasitoid species assumed to be independently distributed as per a Gamma distribution. In such models, the heterogeneity in host risk to each parasitoid is quantified by the corresponding Coefficient of Variation (CV). Our results show that parasitoid coexistence occurs for sufficiently large reproduction rate, if and only if, the sum of the inverse of the two CV squares is less than one. This result generalizes the “CV greater than one” rule that defined the stability for a single parasitoid-host system to a multi parasitoid-host community.

Modeling Climatic Influences on Three Parasitoids of Low-Density Spruce Budworm Populations. Part 1: Tranosema rostrale (Hymenoptera: Ichneumonidae)

Despite their importance as mortality factors of many insects, the detailed biology and ecology of parasitoids often remain unknown. To gain insights into the spatiotemporal biology of insect parasitoids in interaction with their hosts, modeling of temperature-dependent development, reproduction, and survival is a powerful tool. In this first article of a series of three, we modeled the biology of Tranosema rostrale at the seasonal level with a three-species individual-based model that took into account the temperature-dependent performance of the parasitoid and two of its hosts. The predicted activity of the first adult parasitoid generation closely matched the seasonal pattern of attack on the spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae). The model predicted 1–4 full generations of T. rostrale per year in eastern North America. The generations were generally well synchronized with the occurrence of larvae of a probable alternate host, the obliquebanded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae), which could be used as an overwintering host. Spatial differences in predicted performance were caused by complex interactions of life-history traits and synchrony with the overwintering host, which led to a better overall performance in environments at higher elevations or along the coasts. Under a climate warming scenario, regions of higher T. rostrale performance were predicted to generally move northward, making especially lower elevations in the southern range less suitable.

Tetrastichus howardi (Hymenoptera: Eulophidae): first report of parasitism in Oxydia vesulia (Lepidoptera: Geometridae)

The adaptation of native lepidopteran species to eucalyptus plantations reduces the productivity of this crop in Brazil. Oxydia vesulia Cramer (Lepidoptera: Geometridae) is a secondary pest, frequently reported in eucalyptus plantations with population outbreaks and economic damages. Methods of biological control of this pest may include the use of the exotic pupae endoparasitoid Tetrastichus howardi Olliff (Hymenoptera: Eulophidae), reported as efficient to controlling lepidopteran pests. The parasitism of O. vesulia caterpillars and pupae by T. howardi was evaluated under controlled conditions (25 ± 1 ºC, 60 ± 20% humidity and 12:12 h L:D). Each O. vesulia caterpillar or pupae was individually placed in a flat-bottom tube with 10 and 15 females of T. howardi for 48h, respectively. The parasitoids were removed after that period, the caterpillars were fed and the pupae were maintained until emergence of the parasitoid or formation of pupae and emergence of adults of this pest. The fourth-instar caterpillars of O. vesulia, after the parasitism period, were kept in pots with Eucalyptus urophylla leaves, changed daily until the end of the experiment. A total of 40% of the caterpillars died before the pre-pupae stage, 40% reached the pupae stage and died due to inadequate adult formation and 20% generated moths, but none adult parasitoid emerged from the caterpillars. All pupae of O. vesulia were parasitized and showed emergence of parasitoids. The parasitism of O. vesulia caterpillars and pupae by T. howardi shows the potential of this natural enemy for the integrated management of this defoliator pest in eucalyptus plantations.

Pontia glauconome Klug, 1829 (Lepidoptera: Pieridae, Pierinae) in south-eastern Turkey: confirmation of breeding populations, with notes on the biology of early stages and on a species of the larval parasitoid Hyposoter Förster, 1869 (Hymenoptera: Ichneumonidae, Campopleginae)

We report on the apparently successful overwintering in Batman and Siirt Provinces, Turkey of Pontia glauconome, a pierid recorded in south-eastern Turkey for the first time in autumn 2016. Details of recent field observations of P. glauconome are provided and we discuss and illustrate early stages found on Reseda aucheri, a possible new host-plant. The route by which P. glauconomemay have entered the country along the Tigris River from Syria is proposed. Larvae were found to have been attacked by a hymenopteran parasitoid species of the genus Hyposoter; the 'mummified' larval skin and the adult parasitoid are illustrated.

Some Aspects of the Biology of Trichopria anastrephae (Hymenoptera: Diapriidae), a Resident Parasitoid Attacking Drosophila suzukii (Diptera: Drosophilidae) in Brazil

Spotted-wing Drosophila, Drosophila suzukii (Matsumura, 1931), is an economic pest of thin-skinned fruit crops. Its control has commonly been carried out through chemical methods. However, given the need to develop safer and environmentally friendly management alternatives, the pupal endoparasitoid Trichopria anastrephae Lima stands out as a potential biological control agent. However, the lack of information on the mass rearing of this parasitoid limits its use. Thus, the objective of our study was to provide information that is useful for rearing T. anastrephae using D. suzukii as a host. The effects of pupal age, exposure time, and pupal density on the parasitism rate were examined, as was the effect of honey provision for extending adult parasitoid longevity. Exposing 15 12-h-old pupae per female for 24 h resulted in higher parasitism rates and a greater number of emerged parasitoids. Males and females of T. anastrephae fed with pure honey (100%) or honey diluted to 50% in water lived longer compared to those fed 10% honey, no food, or only water.

Use of Flowering Plants to Enhance Parasitism and Predation Rates on Two Squash Bug Species Anasa tristis and Anasa armigera (Hemiptera: Coreidae)

A two-year study evaluated the effect of a flowering border of buckwheat Fagopyrum esculentum Moench on rates of egg parasitism, egg predation and adult parasitism on two squash bug species, Anasa tristis (DeGeer) and Anasa armigera Say, by comparing rates in squash fields with and without a flowering border. Furthermore, we evaluated whether there was an edge effect by comparing parasitism and predation rates in plots located in the corner of a squash field with plots located in the center of a squash field for fields with and without a flowering border. The egg parasitism rates were not affected by either treatment (flowering border or control) or plot location (edge or center). Anasa armigera egg masses only accounted for 4.3% of the total egg masses collected. The egg parasitism rates increased gradually throughout the season, peaking in the last week of August in 2017 at 45% for A. tristis egg masses. The most common egg parasitoid recovered was Gryon pennsylvanicum (Ashmead) followed by Ooencyrtus anasae (Ashmead). Adult parasitism was not affected by treatment, but A. tristis adult parasitism rates were higher in plots located on the edge of squash fields compared with plots located in the center of squash fields in 2016. Since adult parasitoid, Trichopoda pennipes (Fabricius) flies were observed visiting buckwheat flowers, future studies could explore the possibility that the flowering buckwheat may have a more impact on adult parasitism if there was a greater distance between fields with and without a flowering border.

Effect of light intensity and nutritional value of food resources on flight response of adult parasitoid, Cotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae)

Cotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae) is the major larval parasitoid of Plutella xylostella (L) (Lepidoptera: Plutellidae), which is a serious pest of cruciferous plants throughout the world. We evaluated the influence of light intensities and feeding conditions on the vertical angle of flight in freshly emerged wasps in a cylinder having diameter 15cm and height 30cm. Light intensity was found to directly affects the flight activity. Increase in light intensity causes increase in vertical flight of the female wasps. However, Increase in light intensity did not influence the inclination of vertical flight in males. Feeding condition was also found to affect the vertical flight of the wasps. Honey odour, from below the flight chamber, arrested the flight of unfed or sucrose fed wasps. However, flight of honey fed wasps was not affected by honey odour. Male flight response was also influenced by feeding condition and light intensity but the response was not as higher as shown by females. The present study is useful for selecting suitable food prior to inundative release of parasitoid in the field at suitable time period of the day.