Development time and morphological characterization of immature stages of Nasonia vitripennis (Walker, 1836) (Hymenoptera: Pteromalidae) in host pupae of Chrysomya putoria (Wiedemann, 1830) (Diptera: Calliphoridae)

ABSTRACT Nasonia vitripennis (Walker, 1836) (Hymenoptera: Pteromalidae) is a parasitoid involved in the biological control of several insects, including blow flies (Diptera, Calliphoridae) of economic importance. The aim of this study was to describe the morphological aspects of the immature stages of N. vitripennis and to record the postembryonic development time, using pupae of Chrysomya putoria (Wiedeman, 1830) as host. The experiment was conducted in a climatic chamber at 27°C/ day and 25°C/ night, with 60 ± 10% relative humidity and 14h photophase. Three experiment were conducted, each one with different host-parasitoid exposure times, of 12 hours, 16 hours and 24 hours respectively. In each experiment, the host:parasitoid relation applied was three host pupae of C. putoria to one parasitoid female. The experiment lasted 17 days, and it was used nine pupae per day totalizing 153 host pupae. The parasitoidism rate was 16.3% (12h), 40.5% (16h) and 94.1% (24h), respectively. The immature development duration of N. vitripennis with 16 and 24 hours of exposure, was as follows: egg stage (1st day), larvae (2nd to 6th day), prepupae (7th day), pupae (from 8th to 13th day) and pharate adult (14th day). The emergence of the adult parasitoids occurred on the 16th and 15th day with the exposure times of 16 and 24 hours, respectively. The exposure period of 24 hours was the ideal to observe the development time and to characterize the immature of N. vitripennis when compared to the 16 and 12 hours.

Assessment of Chestnut Gall Toughness: Implications for a Biocontrol Agent.

(1) Torymus sinensis, the biocontrol agent of the Asian chestnut gall wasp Dryocosmus kuriphilus, is univoltine, but in NW Italy a small percentage of individuals exhibits a prolonged diapause, mainly as late instar larva. (2) In 2020, the diapause was investigated to evaluate its trend over the years. Due to the low survival rate of diapausing T. sinensis adults, the seasonal variation in the galls' toughness was evaluated, thus assuming that dry galls over time can negatively affect emergence. The window of vulnerability of the gall wasp galls was also evaluated in controlled conditions. (3) The results showed that the average number of second year T. sinensis emerging per 100 cells was 0.41 ± 0.05, and dead adults accounted for 4.1 ± 0.23 per 100 cells. Gall toughness resulted in lower values for galls collected in May and June, and then gradually increased over time. In general, no difference was detected in the wall toughness of galls formed during the previous year when compared to current-year dry galls. Oviposition was recorded on all the tested galls collected in May and June, and no difference in the number of oviposition events was detected. Conversely, no oviposition was observed in July. Comparing the number of oviposition events by T. sinensis and the gall toughness, a negative correlation was found (R2 = -0.99). (4) The present findings contribute descriptive information on this gall's structural traits, and the influence on gall wasp management is also discussed.

Host Specificity of the Parasitic Wasp Anaphes flavipes (Hymenoptera: Mymaridae) and a New Defence in Its Hosts (Coleoptera: Chrysomelidae: Oulema spp.).

The parasitic wasp Anaphes flavipes (Förster, 1841) (Hymenoptera: Mymaridae) is an important egg parasitoid of cereal leaf beetles. Some species of cereal leaf beetle co-occur in the same localities, but the host specificity of the wasp to these crop pests has not yet been examined in detail. A lack of knowledge of host specificity can have a negative effect on the use of this wasps in biological control programs addressed to specific pest species or genus. In this study, laboratory experiments were conducted to assess the host specificity of A. flavipes for three species of cereal leaf beetles (Oulema duftschmidi Redtenbacher, 1874, Oulema gallaeciana Heyden, 1879 and Oulema melanopus Linnaeus, 1758) in central Europe. For the first time, a new host defence against egg parasitoids occurring in O. gallaeciana from localities in the Czech Republic, a strong dark sticky layer on the egg surface, was found and described. The host specificity of A. flavipes was studied in the locality with the presence of this defence on O. gallaeciana eggs (the dark sticky layer) (Czech Republic) and in a control locality (Germany), where no such host defence was observed. Contrary to the idea that a host defence mechanism can change the host specificity of parasitoids, the wasps from these two localities did not display any differences in that. Respectively, even though it has been observed that eggs with sticky dark layer can prevent parasitization, the overall rate of parasitization of the three species of cereal beetles has not been affected. However, in our view, new host defence can influence the effects of biological control, as eggs of all Oulema spp. in the locality are protected against parasitization from the wasps stuck on the sticky layer of the host eggs of O. gallaeciana.

Modeling the Influence of Ambient Temperature on the Interactions Between the Stable Fly (Diptera: Muscidae) and Its Natural Enemy Spalangia cameroni (Hymenoptera: Pteromalidae) to Assess Consequences of Climate Change.

A simulation model was used to predict how temperature influences biological control of stable flies (Stomoxys calcitrans (L.)) by the pupal parasitoid Spalangia cameroni. Temperature, which was either constant or fluctuated due to seasonal variation and/or environmental stochasticity, was modeled as a first order autocorrelation process. The simulations showed that stable flies could tolerate a wider temperature interval than expected from their thermal performance curve (TPC). This was attributed to the fact that immature flies develop in manure, which protects them against low air temperatures. In contrast, the parasitoids were found to have a narrower thermal tolerance range than expected from their TPC. This was attributed to the temperature-dependent functional response of S. cameroni, which was a limiting factor for the parasitoid's development and survival when host densities were low at suboptimal temperatures. The effects of seasonal variation on critical thermal limits were studied by means of thermal performance diagrams (TPDs). Fluctuating temperatures narrowed the thermal tolerance range of both species. At constant temperatures, the simulations showed that the optimal temperature for using S. cameroni in control of stable flies is ~20°C and that the parasitoid can persist in environments with yearly average temperatures between 18 and 29°C. However, if temperature variation was taken into consideration, it changed both the optimal temperature and the temperature interval at which biological control will be possible. This indicates that climate change causing increasing temperatures compounded with greater fluctuations may have serious consequences for biological control of pests.

An Unprecedented Record of Parasitoidism of Formicidae by a Sarcophagid Fly / Um registro sem precedentes de parasitoidismo de Formicidae por uma mosca sarcófaga

Abstract: The first case of parasitoidism of a Myrmicinae ant by a sarcophagid fly has been observed in the Brazilian Cerrado. The larva of a Helicobia Coquillet (Sarcophagidae) specimen fed on head tissues of an Atta laevigata Smith, 1858 soldier and an adult male fly emerged from a puparium formed outside the host.

Resumo: O registro do parasitoidismo de uma formiga Myrmecinae por uma mosca Sarcophaginae foi relatado no Cerrado brasileiro. A larva de um exemplar de Helicobia Coquillet (Sarcophagidae) se alimentou dos tecidos da cabeça de um soldado de Atta laevigata Smith, 1858 e um adulto macho emergiu de um pupário que se formou fora do hospedeiro.

Effects of Extrinsic, Intraspecific Competition and Host Deprivation on the Biology of Trichopria anastrephae (Hymenoptera: Diapriidae) Reared on Drosophila suzukii (Diptera: Drosophilidae).

The pupal parasitoid Trichopria anastrephae Lima (Hymenoptera: Diapriidae) shows potential to control Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), and understanding the behavior of this parasitoid in challenging environments is important to obtain a higher efficiency in mass rearing and in biological control programs. This study aimed to verify the effects of extrinsic intraspecific competition and the absence of host on the parasitism of T. anastrephae in D. suzukii pupae. Therefore, to evaluate the parasitism of T. anastrephae under intraspecific competition, groups of 20 pupae (24 h old) of D. suzukii were offered for different densities of parasitoids (1, 3, 5, or 10 couples) during a 7-day period. Whereas to evaluate the effects of host deprivation on parasitism of T. anastrephae, we tested different treatments: T1-no deprivation, T2-complete deprivation, T3-deprivation every other day, T4-deprivation for 3 days, and T5-deprivation for 7 days. The increase of density of parasitoids resulted in an increase of oviposition scars on pupae and a longer biological cycle, suggesting the occurrence of superparasitism. Increased density also resulted in a higher percentage of attacked pupae, but did not affect parasitoids emergence nor sex ratio. Host deprivation affected number of parasitized pupae, number and sex ratio of offspring, and the longevity of females. Based on our findings, competition among females do not impair offspring viability, and host deprivation for a period up to 7 days do not influence parasitism capacity, indicating that it can be used as a pre-release strategy.

Thermal Requirements and Performance of the Parasitoid Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) on Helicoverpa armigera (Lepidoptera: Noctuidae) Eggs Under Variable Temperatures.

Temperature causes physiological and behavioral changes in egg parasitism. Egg parasitoids are a possible alternative for the control of Lepidoptera pests. The cotton bollworm Helicoverpa armigera (Hübner) is a generalist pest that has recently been introduced into Brazil. We evaluated the suitability of H. armigera eggs as hosts for Trichogramma pretiosum Riley and the effects of temperature (18-33°C) on its survival and development. We assessed the developmental time (egg adult), thermal requirements, age-specific fertility, and parasitism rate upon eggs of H. armigera at six different temperatures. Linear and nonlinear (Brière2) models were fitted to our data in order to describe the relationship between developmental rate and temperature for the immature stages of T. pretiosum and estimate the thermal constant (K), lower developmental temperature threshold (LT), optimum temperature for development (Topt), and upper developmental temperature threshold (Tmax). The estimated K and LT estimated by linear model were 130.38 degree days and 10.3°C, respectively. The T0, Topt, and Tmax by Brière model were 11.52, 32.89, and 41.1°C, respectively. Females of T. pretiosum developed at each temperature were assessed, and parasitism rate was above 75% on the first day, except at 30°C where it took 2 d to reach 75%. At 33°C, the highest rate of parasitism was 38%. The life table parameters predict population increases across the temperature range evaluated. The results demonstrated that T. pretiosum are suitable for the control of H. armigera, and the best performance will be achieved when used in regions with temperatures up to 30°C.

Multiple coexistence equilibria in a two parasitoid-one host model.

Briggs et al. (1993) introduced a host-parasitoid model for the dynamics of a system with two parasitoids that attack different juvenile stages of a common host. Their main result was that coexistence of the parasitoids is only possible when there is sufficient variability in the maturation delays of the host juvenile stages. Here, we analyze the phenomenon of coexistence in that model more deeply. We show that with some distribution families for the maturation delays, the coexistence equilibrium is unique, while with other distributions multiple coexistence equilibria can be found. In particular, we find that stable coexistence does not necessarily require mutual invasibility.

Produção de formas aladas em colônias de Brevicoryne brassicae (L. ) (Hemiptera: Aphididae) por indução do parasitóide Diaeretiella rapae (McIntosh) (Hymenoptera: Aphidiidae) e alguns aspectos comportamentais da interação destas espécies / Production of winged morphs in colonies of Brevicoryne brassicae (L. ) (Hemiptera: Aphididae) induced by the parasitoid Diaeretiella rapae (McIntosh) (Hymenoptera: Aphidiidae) and some Behavioral aspects of the interaction between these species

O objetivo deste trabalho foi o de verificar se há indução de indivíduos alados em colônias de Brevicoryne brassicae (L.), quando expostas a Diaeretiella rapae (McIntosh). Foram também descritos alguns aspectos das interações biológicas dessas espécies. Colônias do pulgão foram iniciadas com 10 adultos por planta de couve, isoladas em recipientes transparentes. Um casal de parasitóides foi introduzido e mantido dentro de cada recipiente-teste por 3h; não foram introduzidos parasitóides do grupo controle. Formas aladas foram produzidas tanto na presença como na ausência de parasitóides, mas, na sua presença, os pulgões alados foram produzidos mais rapidamente e em número significativamente maior. Não se obteve correlação significativa entre o número de alados e o número de múmias. A longevidade média foi de 2,3 ± 0,19 dias e a taxa de parasitoidismo foi em média de 20,6 ± 5,21 por cento. B. brassicae respondeu à presença de D. rapae com aumento na produção de formas aladas. Isto pode ser considerado um mecanismo de defesa, pois os pulgões poderiam, estrategicamente, manter sua sobrevivência, escapando pelo vôo e colonizando outras plantas hospedeiras. Dois outros comportamentos de defesas foram registrados: agitação vigorosa do corpo e fuga dos parasitóides. Durante 26h de observação, foram catalogados 20 atos comportamentais de D. rapae, divididos em cinco categorias: auto-limpeza, alimentação, exploração, cópula e oviposição. Interações diretas entre as espécies ocorreram não somente durante a oviposição, mas também quando a vespa tocava os pulgões com as antenas e ovipositor.

The objective of this study was to verify whether winged morphs are induced in colonies of Brevicoryne brassicae (L.) by exposure to Diaeretiella rapae (McIntosh). Behavioral aspects of the interaction between these species were also described. Aphid colonies were initiated by transferring ten adults to each cabbage plant, kept inside transparent recipients. In the treatment, a parasitoid couple was released inside each recipient-test, and the female was allowed to oviposit freely for 3h; no parasitoids were released in the control recipient. Winged morphs were produced in both conditions, but in the presence of the parasites, their number was significantly higher and they were produced earlier. No significant correlation was obtained between the number of winged individuals and the number of mummies. Parasitoids' longevity was 2.3 ± 0.19 days and the parasitoidism percentage was 20.6 ± 5.21. The increased production of winged morphs in B. brassicae clones in response to the presence of the parasitoid D. rapae can be considered a defense mechanism, because aphids could strategically maintain the clone survivorship, escaping by flight to form a new colony in other plants. Two other types of defense behavior were described: vigorous body shaking and escaping from the parasitoids. During 26h of observation, 20 types of D. rapae behavior were recorded and divided into five categories: self-cleaning, feeding, exploitation, copulation, and oviposition. Direct interactions between these species occur not only during oviposition, but also when the wasp touches the aphids with their antennae and ovipositor.