Influence of larval rearing temperature on the quality of cold‐stored Oomyzus sokolowskii Kurdjumov (Hymenoptera: Eulophidae)

Oomyzus sokolowskii, an important parasitoid of Plutella xylostella, has great potential for use in biological control. Storage at suboptimal temperature is valuable for increasing the shelf‐life of insect parasitoids. In this study, O. sokolowskii larvae were reared at 30/25, 25/25 and 25/20°C light/dark (65 ± 5% RH, 16 : 8 h L : D) until pupation. The pupae were then cold‐stored at 4 ± 1°C (60 ± 5% RH, full darkness). The pupae were removed out from the storage at 10, 20, 30 and 40 days after storage (DAS) and maintained at 25 ± 2°C until adults emerged or pupae died. Quality of the emerging adults and their F₁ offspring were assessed. Incidence of parasitism by O. sokolowskii was higher at 30/25°C than at 25/20°C. Cold storage of O. sokolowskii pupae greatly affected the fitness of the parasitoid: adult emergence rates were lower in the 40 DAS treatment than in other treatments; when O. sokolowskii larvae developed at 25/25°C, female proportions of the emerged adults were lower in the 40 DAS treatment than in the 0 and 10 DAS treatments. Larval rearing temperature mildly affected the adult emergence rate, post‐storage developmental time and female proportion with a few exceptions. Number of parasitoids emerged per host pupa, and incidence of parasitism by the females were neither affected by larval rearing temperature nor cold storage duration. Trans‐generational effects on F₁ offspring were evident in adult emergence rate, egg‐adult developmental time and female proportion which were negatively affected by long duration of storage (40 days), but not by larval rearing temperature with a few exceptions. In conclusion, O. sokolowskii pupae could be stored at 4°C for up to 30 days without significant fitness loss.     

An in-depth study of the larval head skeleton and the external feeding structures related with the ingestion of food particles by the eristaline flower flies Eristalis tenax and Eristalinus aeneus

There is an important lack of knowledge regarding the mechanisms and morphology of the structures involved in the feeding process of the bee-mimicking eristaline flower fly species (Diptera: Syrphidae). In order to look more deeply into their larval feeding biology, a morphological study of the head skeleton and the external feeding structures of the three larval instars of Eristalis tenax (L.) and Eristalinus aeneus (Scopoli), important pollinators and bioindicators of water quality, was carried out, using scanning electron microscopy and confocal laser scanning microscopy. Additionally, an analysis of the ingested particle size was conducted, using various pollen grains and fungal spores. The main differences, found between the third instars of both species, consisted of the more restrictive mandibular lobes of E. tenax, which prevent the ingestion of bigger particles, and a wider filtering area in the cibarium of E. aeneus, which increases the number of particles that can be retained and ingested. Eristalinus aeneus is able to ingest bigger particles (80–100 μm) than E. tenax (70–80 μm). These results suggest that the structures involved in the feeding process of E. aeneus are less restrictive, thus increasing its survival chances when, under artificial rearing conditions, the same medium is used for both species. This study may contribute to the improvement in artificial rearing for future studies on pollination and decomposition.     

Relationship between a metabolic rhythm and emergence rhythm in Drosophila melanogaster

Oxygen consumption and lactic acid dehydrogenase (LDH) activity were determined for Drosophila melanogaster pupae and pharate adults exposed to 12 : 12 or 1 : 23 light-dark (LD) regime. Bimodal circadian fluctuations of oxygen consumption were found in pupae and pharate adults exposed to either LD regime and organisms appeared to demonstrate an anticipatory change in oxygen consumption associated with change in illumination. The oxygen-consumption trend for the entire period spent in the puparium showed a high at the time of emergence, but the diurnal rhythm showed a low at the time of emergence suggesting that emergence occurs at a low in the diurnal cycle. Emergence maximum showed a 3 hr lead over the oxygen-consumption maximum. Changing the LD regime produced similar changes in the phasing of both oxygen consumption and emergence rhythms. LDH activity did not demonstrate a detectable circadian rhythm but did show a steady decrease during pupal and pharate adult development.     

Parasitism and oviposition of Melittobia acasta on Bombus terrestris: Impact of larval overwintering and host status on pupation and adult emergence

Melittobia acasta (Walker) are microhymenopteran ectoparasitoids of the pupae and prepupae of the commercially‐used pollinator bumblebee species Bombus terrestris L. The female parasitoids puncture the host cuticle with their sting and feed oozing hemolymph. This study shows that M. acasta parasitize 100% pupae and 84% prepupae of B. terrestris but are ineffective on the larvae of the bees. The female parasitoids lay a significantly higher number of eggs on pupae (67.7 ± 16.2 female^?1) compared to prepupae (20.5 ± 14.5 female^?1). The parasitoids differ in their choice for oviposition sites and fecundity on different locations of B. terrestris pupae, and they show most preference for oviposition (32%) as well as fecundity (34.9 ± 15.1 female^?1) on the petiole of the host. Larvae of the parasitoids overwinter at low temperatures but larval overwintering duration and post‐diapause rearing on original or new hosts do not affect their pupation and adult emergence. Larvae have a higher percentage of pupation (88.0–94.4%) and adult emergence (84.4–92.9%) both on the original and the new host, thus indicate that the parasitoids are highly capable of reproduction in B. terrestris colonies.     

Host-independent artificial rearing of Eucryptorrhynchus brandti (Coleoptera: curculionidae)†

Eucryptorrhynchus brandti (Harold) is a trunk boring pest of Ailanthus altissima in China and is a potential biological control agent for invasive A. altissima in the USA. In this study, we developed a host-independent artificial rearing method for E. brandti adults and larvae, including fresh thin slices of potato for adults and a potato-based diet (referred to as diet 6) for larvae. Adults reared on thin slices of potato oviposited normally and larvae reared on diet 6 exhibited successful pupation and eclosion and short developmental duration. The rates of larval survival, pupation, and adult emergence were 63.3?±?0.26, 86.7?±?0.42, and 93.5?±?0.33%, respectively. This method could be used for the mass rearing of E. brandti.     

Demography and population parameters of two species of eristaline flower flies (Diptera,Syrphidae, Eristalini)

The importance of eristaline flies (Diptera, Syrphidae, Eristalini) as pollinators in natural ecosystems and for agricultural crops is well known. However, in-depth studies on the life cycle of most of these species have yet to be carried out. The aim of this research was to study the life cycle of Eristalis tenax (Linnaeus, 1758) and Eristalinus aeneus (Scopoli, 1763) in order to improve the current rearing system employed at the University of Alicante. The results were analysed using the age-stage, two-sex life table method. As one of the main results, the mean duration of the life history of E. tenax and E. aeneus was 46.06 and 65.12 days (d), respectively. The most critical step for both species was found at the beginning of the larval stage (first instar), when the highest mortality was recorded. Population parameters were also analysed and compared. The intrinsic rate of increase (r), the finite rate of increase (λ), the net reproductive rate (R₀) and the mean generation time (T) were 0.09 (d⁻¹), 1.09 (d⁻¹), 42.11 offspring and 40.97 d, in the case of E. aeneus and 0.05 (d⁻¹), 1.05 (d⁻¹), 23.13 offspring and 59.23 d, in the case of E. tenax. These results indicate that the current rearing system is more efficient for E. aeneus, which displays a faster population growth. However, some modifications need to be implemented to improve the production of E. tenax.     

Influence of Ground Predators on the Survival of the Mediterranean Fruit Fly Pupae, Ceratitis capitata, in Spanish Citrus Orchards

A survey of predaceous ground arthropods was conducted in two citrus orchards in Valencia, Spain, and their role as predators of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) pupae was evaluated under field and laboratory conditions. A total of 2959 predaceous arthropods were collected in pitfall traps in the two orchards from July 2003 to September 2004. Ants (Hymenoptera) were the most abundant group (83.61%), followed by Staphylinidae (7.77%), Araneae (5.24%), Dermaptera (2.13%), Carabidae (0.64%) and Cicindelidae (0.61). Pupae disappearance rates were higher during the warmer months of the year, from May to October, and in the orchard with the largest ant population. In the warm season, the mean survival of C. capitata pupae was 35.7±6.2% and 14.3±6.7%, respectively, in both orchards. Patterns of predation, inferred from broken or abnormal pupae, were more frequently observed in the colder months, from November to April, when spiders, Staphylinidae and other predators were present. In the cold season, the combined effect of predation and low temperature led to an adult emergence rate of 26.7±9.9% and 13.0±7.5% in both orchards. In no-choice laboratory trials, all predator species tested fed at significantly different rates on C. capitata pupae. Preliminary data show that the Carabids, Pseudophonus rufipes (Duftschmid) and Harpalus distinguendus (Degeer), were the most voracious species, consuming more than one pupa per day.     

Superparasitism in mass reared Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), a parasitoid of fruit flies (Diptera: Tephritidae)

Superparasitism frequency and its effects on the quality of mass-reared Diachasmimorpha longicaudata (Ashmead) parasitoids were investigated under laboratory conditions. Percentage of adult emergence, sex ratio, survival, fecundity and flight ability of adult parasitoids that emerged from Anastrepha ludens (Loew) pupae with different levels of superparasitism were determined. A high prevalence of superparasitism was observed. The number of scars per pupa, produced by insertion of the parasitoid ovipositor, ranged from 1 to 30, with an average (±SD) of 8.3 ± 6.2. Adult parasitoid emergence decreased as the level of superparasitism increased. However, the fraction of females rose with increasing superparasitism and the flight ability was lower in adults emerging from pupae with only one scar, compared with adults emerging from superparasitized hosts. Female longevity and fecundity were not affected by superparasitism. Our results support the hypothesis that superparasitism in D. longicaudata might be adaptive, since adults emerging from hosts with moderate levels of superparasitism showed the highest percentage of emergence and there were no significant differences in the other quality control parameters tested. Our findings are relevant to the mass rearing process, where the ratio of hosts to parasitoids can be optimized as well as the distribution of eggs deposited in host larvae. This contributes to efficient mass rearing methods for augmentative biological control programs.     

Effects of host stage on the development of the facultative autoparasitoid Encarsia tricolor (Hymenoptera: Aphelinidae)

Encarsia tricolor is a facultative autoparasitoid of the glasshouse whitefly, Trialeurodes vaporariorum, with a potential in biological control. The rate of development, number of mature oocytes at emergence, number of ovarioles and size of the emerged adults were studied. Five nymphal instars (N1, N2, N3, N4, and pharate adult) of T. vaporariorum were used as hosts for the females. Female larvae and pupae of E. tricolor and Encarsia formosa were used as hosts for the males. Females developed faster when the egg was laid on N3 (18.0 days from egg to adult) and slower on N1 (22.3 days). Females were bigger when developing from N1 and N3 than from N4 and pharate adult. On emergence the mean number of mature oocytes was always small (0.8–2.6). Males developed faster and were smaller than females, and developed faster and were larger on larvae of E. formosa.     

Carbohydrate metabolism during the pupal molt of the tobacco hornworm,Manduca sexta

During the pupal molt of the tobacco hornworm, Manduca sexta, the percentage of active fat body glycogen phosphorylase increased from 5–10 to 20%, but only for a period of 5 h prior to the molt. From the time of the appearance of two sclerotized dorsal bars to the time of the molt, the concentration of total hemolymph carbohydrates doubled to 100 mM trehalose. Initially, the glucose level was high (16 mM) when compared with feeding larvae (approximately 1 mM) but decreased to zero just prior to the molt. The amount of cuticular chitosan decreased from approximately 100 mg to 10 mg at pupation; the exuvia contained approximately 7 mg. While the levels of total lipids in hemolymph were not affected, the lipid content of the fat body decreased significantly prior to the molt but increased sharply thereafter. Fat body glycogen phosphorylase in pharate pupae and pupae of M. sexta was substantially activated by the Manduca adipokinetic peptide hormone, which in pharate pupae, produced the same response at 2 and 20 pmol per insect as in ligated larval abdomens. In pupae the response was clearly reduced. Using chilling to stimulate glycogen phosphorylase, it was found that the enzyme in pharate pupae and pupae responded both in vivo and in vitro as in ligated abdomens of larvae. Thus, a transition to the adult response seems to occur during the pupal and pharate adult development. © 1995 Wiley-Liss, Inc.     

Use of day-degree estimates for rearing management of Ctenopseustis obliquana (Lepidoptera: Tortricidae) in the laboratory

Abstract

The brownheaded leafroller (BHLR), Ctenopseustis obliquana (Walker) (Lepidoptera: Tortricidae) was reared on an artificial diet at seven constant temperatures. The mean life cycle at optimum rearing temperature of 20 ± 1°C was: egg development 8.7 days; larval period, M 37.4, F 41.2 days; pupal period, M 14.9, F 13.3 days; pupal weights, M 50.5, F 68.2 mg; and a fecundity of 670 eggs per female. Estimated lower threshold temperatures and mean cumulative number of day- degrees for various stages of development were 7.8°C and 105D° for eggs, 5.2°C and 538D° for larvae, and 7.2°C and 186D° for pupa. Total mean day-degree accumulation from egg to adult was 829D°.

These data were used to develop an efficient rearing management system embracing colony maintenance, storage, manipulation, production, and quality assessment procedures.     

Effects of short-term heat stress on the growth and development of Bradysia cellarum and Bradysia impatiens

Bradysia cellarum Frey and Bradysia impatiens Johansen are major pests of vegetable crops, as well as edible mushrooms and ornamental plants, and damage to hosts resulting in economic losses. Temperatures above the optimum levels for these pests have been predicted to regulate their population growth during summer. The aim of the present study was to examine the effects of both heat stress and exposure time on the growth and development of eggs, larvae and pupae for two Bradysia species. The egg stage, egg hatching rate, 4th instar larval stage, pupation rate, pupal stage and adult emergence rate were observed after exposing at high temperatures of 34°C, 37°C and 40°C for 1, 2, 4 and 6 hr. The results showed that 34°C, 37°C and 40°C for 1-, 2-, 4- and 6-hr exposure treatments prolonged the developmental stage of egg, 4th instar larva and pupa, while decreasing the egg hatching rate, pupation rate and adult emergence rate. This suggests that increasing temperature or prolonging exposure time to the heat stress could significantly affect insect survival, growth and development. Our study could provide an ecological basis for pests’ management strategy by using short-term heat stress.     

温度对黑纹粉蝶越冬蛹滞育后发育的影响

为了探讨温度对黑纹粉蝶Pieris melete越冬蛹滞育后发育的影响, 系统调查了越冬蛹滞育解除后在不同恒温下的发育历期及其在自然条件下春后的羽化情况。结果表明: 黑纹粉蝶雄虫和雌虫越冬蛹滞育后发育的阈值温度分别为7.1±1.5℃ 和7.4±0.4℃, 滞育后发育的有效积温分别为133.4±3.3日·度和155.7±5.3日·度。根据连续7年黑纹粉蝶越冬蛹在田间的羽化情况, 结合当年春季滞育后发育阈值以上的温度, 推算出田间50%个体成虫羽化时雄虫和雌虫获得的有效积温分别为142.2±12.2日·度和149.2±13.8日·度, 与滞育后发育的理论有效积温接近。据此, 利用该理论上的发育阈值温度和有效积温, 参照当年2-4月的气温, 可预测田间越冬蛹50%个体成虫羽化的时间。     

Morphogenetic effects of juvenile hormone and juvenile hormone mimics on adult development of Drosophila

The morphogenetic effects of t,t-farnesol, Law-Williams juvenile hormone analogue, dichlorofarnesenic acid ethyl ester (DFAEE), and a syntetic racemic or isomeric mixture of C₁₈ juvenile hormone (JH), when applied topically to pharate pupae and adults of D. melanogaster have been studied. Of these various agents tested, only DFAEE and JH affected adult development and eclosion and the pharate pupae were the most sensitive to these agents. The racemic mixture of JH induced the secretion, in the abdomen, of a supernumerary cuticle indistinguishable from that of the pupa; it, in addition, retarded the synthesis of brown eye pigments, general body pigmentation, and affected the differentiation of various internal organs and cuticular structures of the abdomen. By comparing the effects of JH with those of Minute (M) and bobbed (bb) mutations on the adult development, it is suggested that JH, by retarding genetic translation mimics M or bb.     

Ecdysteroids and diapause in pupae of Heliothis punctiger

Most pupae of H. punctiger enter diapause when reared at 19°C, 12L:12D. When pharate pupae were treated for only 12 hr at 28°C about 50% developed at 19°C. The proportion of non-diapausing pupae increased as the temperature at which the pharate pupal stage was spent increased.The quantity of injected 20-hydroxyecdysone necessary to promote development in diapausing pupae varied from about 1 μg g^?1 soon after pupation to about 4 μg g^?1 after 50 days. It fell somewhat after 150 days.Removing brains from non-diapausing pupae showed that the brain secreted its hormone at the time of pupation (or just before). However, if the pupae were kept at 19°C development did not occur unless the brain remained in situ for at least 20 hr at 28°C. Implanting brains from non-diapausing pupae into diapausing ones had no measurable effect.These results may be explained by postulating that the prothoracic gland is ‘activated’ by exposure to high temperature, but that it reverts to inactivity over a period at 19°C. The ‘active’ gland must then be stimulated by brain hormone for a long period to trigger secretion of its hormone, which results in development. Diapause is thus the result of the failure of the prothoracic gland to secrete.     

Impacts of two conventional insecticides on different stages of Encarsia inaron Walker parasitizing the whitefly,Trialeurodes vaporariorum Westwood under greenhouse condition

In this research, for the first time, compatibility of imidacloprid and pyriproxyfen was assayed with both pupa and adult stages of Encarsia inaron Walker parasitizing Trialeurodes vaporariorum Westwood. First, the insecticides were sprayed on bean plants containing the parasitoid pupae, thenceforth, survival of the adult parasitoid was evaluated 24 h post-exposure to fresh, 1-, 4-, 7-, 14-, and 21-day-old residues of them on bean leaflets in Petri dishes. Both insecticides significantly reduce E. inaron adult emergence. Mortality of the parasitoid pupa in treatment with imidacloprid (69.7%) was significantly higher than mortality with pyriproxyfen (28.6%). Pyriproxyfen was non-toxic to the adult parasitoid when residues were dried in fresh and aged through the experiment, while in the same condition, imidacloprid significantly killed the adult parasitoids up to 7 days after application. Results have been discussed on the potential compatibility of the insecticides with E. inaron in an integrated pest management (IPM) approach.     

Effect of temperature on the development time and life-time fecundity of Trichopria anastrephae parasitizing Drosophila suzukii

The aim of this study was to evaluate the effect of temperature (10, 15, 20, 25, 30 and 35°C), on the development time and life-time fecundity of Trichopria anastrephae Lima, 1940 (Hymenoptera: Diapriidae) parasitizing Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae). D. suzukii pupae that were up to 24-hr old were submitted to T. anastrephae parasitism for 24 hr. They were placed in plastic containers (50 ml) (ten pupae per container) in climatic chambers at temperatures of 10, 15, 20, 25, 30 and 35°C ± 1°C with a relative humidity of 70% ± 10% and a 12 hr photoperiod. For the adult phase, T. anastrephae couples that were up to 24 hr old were each placed in plastic cages (300 ml) and kept at the same temperatures cited above until their deaths. The higher numbers of parasitism and offspring production were obtained at temperatures between 15 and 25ºC. At the temperatures of 10 and 35ºC, there was no emergence of individuals. The lower thermal threshold (Tt) for the egg to adult period was ≈ 14.6°C for males and females with thermal constants (K) of 384.61 and 432.90, respectively. In terms of the fertility life table, T. anastrephae at 20 and 25°C presented shorter generation time (T) and higher net reproductive rates (Ro) in relation to other temperatures. The data show the ability of T. anastrephae to adapt to different thermal conditions, which is important for biological control programmes of D. suzukii.     

甜菜夜蛾人工饲料及饲养技术研究

研究了人工继代繁殖甜菜夜蛾饲料配方及饲养方法 ,测定了各虫态发育历期、幼虫死亡率、化蛹率、羽化率、蛹畸形率及不同世代蛹重。采用改进的饲料配方饲养的深圳种群 ,第 2代幼虫死亡率、化蛹率、蛹畸形率、羽化率分别为 7 8% ,97 3 % ,2 7%和 93 8% ,第 2 ,5 ,9,1 2代平均单头蛹重分别为 1 1 9 7± 1 6 1 ,98 3± 1 1 4,94 3± 1 2 6和 82 4± 9 6mg,平均单雌产卵量分别为 1 1 3 7 2± 63 3 ,684 5± 5 3 7,45 6 9± 40 2和 3 91 7± 45 6粒。人工饲养的甜菜夜蛾 ,卵、幼虫、蛹、雌性成虫的发育历期分别为 2 5～3 5 ,1 0～ 1 2 5 ,7～ 8 5和 8～ 1 4天 ,完成一个世代需要 2 1～ 2 5天。     

In vitro rearing of Ooencyrtus nezarae (Hymenoptera: Encyrtidae), an egg parasitoid of Riptortus pedestris (Hemiptera: Alydidae)

Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) is a polyphagous egg parasitoid of various true bugs, including Riptortus pedestris (Fabricius) (Hemiptera: Alydidae), a major pest of soybean and fruit trees in northeastern Asia. This study was conducted to develop artificial host eggs containing insect haemolymph for mass rearing of O. nezarae. The haemolymph of Chinese oak silkworm (Antheraea pernyi Guérin-Méneville) pupae was found to be most suitable for artificial eggs for the complete development of O. nezarae. Among 764 parasitoid eggs laid in artificial eggs, 49.2% successfully developed to adult parasitoids. The developmental time in artificial eggs was delayed by 3–5 days relative to that observed in natural host eggs; however there was no significant difference in the length of hind tibia between adults that emerged from artificial and natural host eggs. Moreover, new generations that emerged from artificial eggs reproduced on all egg types offered (either natural or artificial eggs). We propose that the artificial eggs developed herein can therefore be an effective means for mass rearing O. nezarae.     

Ecdysteroid profiles for hemolymph and testes from larvae,pupae, and pharate adults of the European corn borer,Ostrinia nubilalis hubner

Total ecdysteroid levels as well as concentrations of several individual ecdysteroids were determined for hemolymph and testes of fifth instars, pupae, and pharate adults of the European corn borer, Ostrinia nubilalis (Hubner). For total levels, the patterns of fluctuation in hemolymph and testes were similar, but the concentrations in testes were lower than those in hemolymph. In both hemolymph and testes there were two ecdysteroid peaks: the first just prior to the formation of the pharate pupa, the second just prior to the formation of the pharate adult. An examination of ecdysteroid profiles revealed some important differences. Ecdysone was either absent or present at extremely low levels in larval testes, whereas in hemolymph there was a premolt ecdysone peak. In pupal testes, ecdysone was present, but levels of 26-hydroxyecdysone were much lower than those in hemolymph. Thus, in regard to ecdysteroids, testes have the ability to control their own internal milieu.