Ephestia Eggs Research Articles

Alternative food sources for Amblydromella caudiglans (Phytoseiidae) and effects on predation.

The addition of supplemental food sources for natural enemies is a growing component of conservation and augmentative biological control. Supplemental foods can be used to retain natural enemies when prey are scarce and to promote survival, fecundity, longevity, and development of natural enemy populations, especially generalist natural enemies. Amblydromella caudiglans (Schuster) (Acari: Phytoseiidae) is one of the most abundant predatory mites found in commercial apple orchards in Washington, USA, and contributes to spider mite control. However, because its widespread presence in commercial apple orchards was only recently discovered, how supplementary food sources affect its performance is unknown. In laboratory studies, we evaluated the performance (fecundity, retention, prey consumption) of the generalist phytoseiid A. caudiglans on commercially available supplemental food sources, including factitious prey (Ephestia eggs and Artemia brine shrimp cysts), and pollens of apple, pear, and cattail. We determined that A. caudiglans will not consume Ephestia eggs and performs best on cattail and pear pollens. Combinations of food sources did not enhance the performance of this predator compared to the best performing single-sources. The presence of alternative food sources did not decrease A. caudiglans predation of twospotted spider mite nymphs, except for Artemia brine shrimp cysts, which had a substantial handling time. These results lay the groundwork for identifying a way to promote and retain this natural enemy in tree fruit cropping systems through the use of food resource applications or floral plantings.

Dietary history modifies the innate responses of lady beetles (Coleoptera: Coccinellidae) to odors of their prey-infested host plants

Oenopia conglobata (L.) and Menochilus sexmaculatus F. are two important predators of pistachio psyllid, a key pest of pistachio in Iran, the former indigenous, and the latter recently adventive. Aphis gossypii Glover infests understory plants in pistachio orchards and is used by both species as an alternative prey when psyllids are scarce. We 'conditioned' beetles by rearing them for five generations on these prey and their respective host plants (Pistacia vera L. and Curcurbita pepo L.), or on eggs of Ephestia kuehniella (Zeller) as a control, and measured the preferences of female beetles for plant and plant/prey odors in an olfactometer. When conditioned on Ephestia eggs, both species found P. vera odors attractive, but not C. pepo odors, and although both plants became more attractive when infested with prey, O. conglobata preferred pistachio/psyllid odors over cucumber/aphid odors, whereas M. sexmaculata showed no preference. Whereas conditioning on pistachio/psyllid caused O. conglobata to prefer (unfamiliar) cucumber/aphid odors, its innate preference for the former disappeared when conditioned on cucumber/aphid. In contrast, conditioning on pistachio/psyllid did not alter the innate responses of M. sexmaculata to cucumber/aphid odors, whereas conditioning on pistachio/psyllid caused odors of this complex to be preferred to those of aphid/cucumber. Thus both species exhibited asymmetric, species-specific responses to conditioning treatments that reflected both innate recognition of plant/prey odors, and some plasticity as a function of recent dietary history, which in some cases led beetles to prefer the novel (unconditioned) plant/prey complex. The observed plasticity of innate olfactory responses as a function of conditioning might be advantageous for generalist predators that must frequently switch among different prey types associated with different plants.

ASPECTOS BIOLÓGICOS DE Ceraeochrysa everes (NEUROPTERA: CHRYSOPIDAE) ALIMENTADA COM COCHONILHA-ROSADA-DO-HIBISCO

ABSTRACT The invasive pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae), is a pest that threatens the production of fruits, vegetable, and ornamental plants in Brazil. It is a phytophagous insect with a wide range of hosts; thus, there is an increasing demand for sustainable environmental-friendly control methods, such as biological control. This study aimed to investigate biological parameters of Ceraeochrysa everes (Neuroptera: Chrysopidae) fed on 2nd instar nymphs of M. hirsutus and eggs of Ephestia (Anagasta) kuehniella (Zeller) (Lepidoptera: Pyralidae). The duration of the immature stages of C. everes was longer when the predator was fed on 2nd instar nymphs of M. hirsutus, compared to the control (E. kuehniella). The survival rate of immature C. everes was 82.5% and 100% when fed on 2nd instar nymphs of M. hirsutus and eggs of E. kuehniella, respectively. The type of food resource offered at the larval stage affected the pre-oviposition, oviposition, and post-oviposition periods and the longevity of C. everes females. Adult females C. everes from immature individuals fed an exclusive diet of E. kuehniella eggs had longer oviposition, fecundity (daily and total), fertility, and post-oviposition periods and longevity. Ceraeochrysa everes has the capacity for predation, development, and reproduction while having 2nd instar nymphs of M. hirsutus as food resource. Therefore, C. everes has a promising potential for controlling M. hirsutus.

Effect of the Amount of Ephestia kuehniella Eggs for Rearing on Development, Survival, and Reproduction of Orius laevigatus.

Simple SummaryEconomical mass rearing of natural enemies is pivotal for their use as augmentative biological control agents. To this end, the conditions for mass production have been widely investigated for different natural enemies, including the predator Orius laevigatus. The key component for cost optimization of production systems is the type and amount of diet supplied. In the case of O. laevigatus, Ephestia kuehniella eggs have proved to be nutritionally superior to other cheaper natural and artificial foods. Consequently, the current practice in industrial production is the use of these eggs as food. Therefore, there is a need to know the minimum amount of Ephestia eggs needed per individual leading to a cost reduction, which in turn will favor biological control adoption. In this study, we established a minimum of 1 and 3 Ephestia eggs per day for the first two nymphal instars, respectively, and 8 eggs per day for subsequent development until adulthood. Benefits and savings for industrial production of O. laevigatus and its use in biological control are discussed.Orius laevigatus is a key tool for the success of augmentative biological control programs in protected crops. This biological control agent is mass-reared feeding on eggs of Ephestia kuehniella. However, this factitious prey is expensive, accounting for a significant percentage of the rearing costs. Therefore, there is a need to optimize the amount of Ephestia eggs needed per individual leading to a cost reduction, which in turn will favor biological control adoption. This study investigated the effect of the amount of Ephestia eggs provided on the developmental and reproductive fitness of O. laevigatus. At least a daily supply of 1 and 3 Ephestia eggs was needed for optimal development of the first two nymphal instars, respectively, although for maximum survival, 1 egg was enough for both instars. For subsequent development until adulthood, a minimum of 8 eggs per day were needed to fully support growth, but only 3 eggs for optimal survival. Similarly, male body size was also maximized by feeding 8 eggs, but for maximum female body size 10 eggs per day were required. Oviposition rate of females increased with the daily number of Ephestia eggs provided, until a plateau was reached at 8 eggs/day. Benefits and savings for industrial production of O. laevigatus are discussed.

Effectiveness of factitious foods and artificial substrate in mass rearing and conservation of Neoseiulus californicus (Acari: Phytoseiidae)

ABSTRACT The use of factitious food instead of natural prey, and artificial substrates instead of leaf-based, could be important steps towards reducing natural enemies̓ rearing costs. Nutritional values of four factitious foods comprising Ephestia eggs, decapsulated Artemia cysts, mould mite immature individuals, and Aspergillus hyphae as alternative food sources for Neoseiulus californicus (McGregor) were determined under laboratory conditions. In addition, suitability of artificial (plastic sheet) and leaf-based substrates for rearing of the predator was assessed. The duration of egg to adult developmental time was shorter when the predator fed on the mould mite compared with the other diets. Artemia cysts and Aspergillus hyphae were not suitable diets. The individuals reared on the mould mite had the highest fecundity and intrinsic rate of increase (r). Due to weak mouthpart of the immature predator in feeding of factitious foods, most of them died in immature stages, or their fecundity in adult stage was low. In a separate experiment, almond pollen was also used in addition to factitious foods for rearing of immature stages of the predator. The adult stage of these individuals had the ability to feed and oviposit on the factitious foods, and female longevity and fecundity of these individuals were higher on E. kuehniella egg (and after that on mould mite) than the others. In addition, the results indicated that the rearing performance of the predator fed on the same diet was higher on the artificial substrate than the leaf-based one. The potential of alternative foods and artificial substrates for mass production and conservation of N. californicus is a suitable and cheap method.

Genetic improvement of Orius laevigatus for better fitness feeding on pollen

In many protected crops, augmentative biological control heavily relies on generalist predators, which continuous presence on the crop allows an early response to pest immigration and outbreaks. Persistence is possible by their ability to feed on alternative food, such as pollen, plant-provided or artificially supplemented. However, fitness is decreased when feeding on alternative foods, hindering performance. We present a new approach to face this challenge: genetic improvement for better fitness feeding on suboptimal food. Orius laevigatus is one of the main biological control agents used in greenhouse vegetable crops. A breeding process was carried out on the basis of a broad intraspecific variability exploration for 10-day fecundity feeding on pollen (14.2–37.9 eggs/female for 30 wild and commercial populations). Life history traits were finally compared between our two selected strains and three commercial, wild and acclimated-to-pollen unselected populations, both on rich (Ephestia eggs) and suboptimal (dry honeybee pollen) diets. Selected lines showed considerably improved values for longevity (1.5-fold), early (1.3-fold) and lifetime fecundity (1.9-fold), nymphal survival (3.5-fold), intrinsic rate of natural increase (rm) (7.3-fold) and net reproductive rate (R0) (6.7-fold) as compared to reference unselected strains when they were fed on pollen, although still lower than on the optimal diet. Selection feeding on plant material resulted in no trade-offs when feeding on the factitious prey. This improvement was due to genetic gain rather than to phenotypic plasticity to tolerate nutritious restriction. Finally, some potential contributions of these improved lines not only for augmentative biocontrol but also for artificial rearing are provided.

The Production of Sex Pheromone in Lady Beetles Is Conditioned by Presence of Aphids and Not by Mating Status.

Female Harmonia axyridis (Coleoptera: Coccinellidae) produce a sex pheromone to attract males. In the present study, we tested two hypotheses: (i) production of sex pheromone in H. axyridis is conditioned by perception of prey in their vicinity, and (ii) virgin females invest in the production of the sex pheromone, while mated females reduce their pheromone emissions. To test the first hypothesis, newly hatched larvae were divided into three groups: those fed with Ephestia kuehniella eggs, those fed with pea aphids, and those exposed to aphid volatile cues but fed with Ephestia eggs. All females produced a pheromone blend of five-components in similar relative proportions, but with contrasting absolute quantities: Females fed with Ephestia eggs produced lower amounts of pheromone (0.5 ± 0.4ng.female-1), compared to females fed with aphids (44.2 ± 24.4ng.female-1). The females of the third group produced intermediate concentrations of pheromone (6.0 ± 3.2ng.female-1). To test the second hypothesis, two groups of lady beetles were made: one group of females was placed in the presence of males, while females of the other group were not. Mated and virgin females produced statistically similar amounts of pheromone (144.1 ± 49.7ng and 43.7 ± 24.1ng.female-1, respectively). These results suggest that H. axyridis females initiate pheromone production upon exposure to volatile cues released by their aphids prey. Females continue to release sex pheromone after mating, probably to increase the chance of multiple mating which is known to improve egg fertility.

Food quality of Ephestia eggs, the aphid Rhopalosiphum padi and mixed diet for Orius majusculus

AbstractWe studied the food quality of the aphid Rhopalosiphum padi to the pirate bug Orius majusculus using Ephestia eggs as high‐quality comparison prey. Several performance parameters were tested on individuals that had been reared and maintained on each of the two single‐prey diets or on a mixed diet. All fitness parameters were lower in individuals fed aphids only, indicating poor food quality of this prey. Compared with the pure Ephestia egg diet, the mixed diet enhanced teneral mass, while adult survival and female starvation tolerance were negatively affected and all other traits were unaffected. Body protein proportions were constant across diets, whereas lipid proportion was low in the aphid treatment. Preference for aphids was lower following a monotypic aphid diet than when reared on Ephestia eggs or a mixed diet. The results confirm that R. padi is low‐quality food for O. majusculus as it is for other generalist predators, even though O. majusculus may contribute significantly to population suppression of the aphid.

The function of supplemental foods for improved crop establishment of generalist predators Orius insidiosus and Dicyphus hesperus

As with many biological control agents, generalist predators rarely survive prolonged periods of prey scarcity. Towards improving crop establishment of two major predators used in North America, Orius insidiosus and Dicyphus hesperus, this study examined the role of supplemental foods in achieving greater predator survival and faster development. In controlled environment trials, developmental time and survival were compared for predators offered diets including Ephestia eggs, Artemia cysts, Typha pollen, or combinations of these. Nymphal developmental time was significantly shorter and survival greater for both predators reared on diets that included Ephestia eggs. Interestingly, D. hesperus could successfully complete nymphal development on Artemia cysts whereas O. insidiosus could not, alluding to fundamental physiological differences between these predators. In greenhouse assays, D. hesperus was more abundant after six weeks when offered diets that included Ephestia eggs either alone or in combination with pollen or Artemia cysts relative to other diets. In contrast, only diets of Ephestia eggs, Typha pollen or their combination could significantly increase O. insidiosus crop abundance relative to the unfed control. Together, this work highlights important differences in the relative values of supplemental foods for generalist predators used in crop protection. It is also meaningful in guiding biocontrol practitioners globally in the rapidly growing sector of greenhouse vegetable production.

Pre-planting inoculation for early establishment of Dicyphus bolivari and D. errans on tomatoes

Slow establishment and risks of plant damage are major constraints for the use of the predatory mirid bugs that are commercially available for release in greenhouse crops. Therefore, a new interest has turned towards two predatory Dicyphus species (Heteroptera: Miridae) that have been investigated in the past but have not been used commercially in augmentative biological control. We assessed their development duration and survival at temperature and day length of summer and winter conditions and assessed the feasibility of pre-planting predator establishment on plant seedlings under those conditions. Dicyphus bolivari (Lindberg) and D. errans (Wolff) nymphs reached the adult stage in 47.4 (winter conditions) and 18.6 days (summer conditions) and 46.0 (winter) and 16.3 days (summer) respectively. They showed more than 90% survival when provided with food (Ephestia eggs). Provision of food allowed females to lay more eggs and to distribute them more evenly among tomato seedlings. No injuries or other negative effects on tomato seedling development were observed. Nymph development time of the two mirid species studied were slightly higher than other commercial mirid predators. The results show great potential of these predatory bugs, which are now being tested under field conditions.

Factitious prey and artificial diets: do they all have the potential to facilitate rearing of Typhlodromus bagdasarjani (Acari: Phytoseiidae)?

ABSTRACTThe rearing possibility of Typhlodromus bagdasarjani (Phytoseiidae) on three factitious prey (Ephestia kuehniella eggs, cysts of Artemia franciscana and Tyrophagus putrescentiae), and nine artificial diets including a basic artificial diet (AD1) and the others (AD2–AD9) consisted of 80% AD1 enriched with different nutrients including maize pollen, haemolymph of Plusia gamma L., Ephestia eggs, Artemis cysts, Ephestia larvae, multivitamin syrup, bovine serum albumin and bull sperm, as well as a natural pollen diet (almond+ maize pollen) were investigated. None of the three factitious prey supported development of T. bagdasarjani beyond protonymphal stage. The highest GRR (gross reproductive rate), R0 (net reproductive rate), r (intrinsic rate of increase) and λ (finite rate of increase) were obtained when the adults were reared on cysts of Artemia, immediately after their emergence. On pollen diet, all population growth parameters except T (mean generation time) were higher than artificial diets. The mites reared on AD6 and AD8 could not develop beyond deutonymphal stage. Although r was negative on both AD3 and AD5, its value on AD3 was higher. In conclusion, except pollen diet, none of diets tested is recommendable for mass rearing of this predator and utilizing on crop as alternative food.

Attempt to Develop Cost-Effective Rearing of Amblyseius swirskii (Acari: Phytoseiidae): Assessment of Different Artificial Diets.

Commercial production of Amblyseius swirskii Athias-Henriot based on storage mites needs both space and labor to maintain large cultures of these prey, and also may lead to health problems for workers. Therefore, the accessibility of a suitable artificial diet could eliminate the mentioned problems; however, the artificial diets must support the persistent production of high quality progeny. This study endeavored to find a more easily available and cheaper nutrient that may further reduce the cost of diet production for A. swirskii. The predator's performance was determined when it was fed on a basic artificial diet (AD1) composed of honey, sucrose, tryptone, yeast extract, and hen egg yolk, and on eight other artificial diets consisting of 80% AD1 enriched with different nutrients including maize pollen (AD2), hemolymph of Plusia gamma L. (AD3), Ephestia eggs (AD4), Artemis cysts (AD5), Ephestia last-instar larvae (AD6), multivitamin syrup (AD7), bovine serum albumin (AD8), and bull sperm (AD9). The lowest development time was on AD2. The highest value of fecundity and oviposition period were observed on AD5, followed by AD2 and AD4. The intrinsic rate of increase (r) and the finite rate of increase (λ) reached the maximal value on AD5. Feeding on AD2 and AD5 resulted in highest value of R0 (net reproductive rate). Our results indicated that Artemia cysts and maize pollen had better potential to be used as nutrient in artificial diet for mass production of A. swirskii. Overall, it seems that AD2 is the most cost effective than others.

Biological control of mealybugs with lacewing larvae is affected by the presence and type of supplemental prey

The diversity of prey and food sources in crops has a major effect on biological pest control by generalist predators. In this study, we tested if and how supplemental prey or food affects the control of the citrus mealybug Planococcus citri (Risso) by larvae of the green lacewing Chrysoperla lucasina (Lacroix). The larvae of this predator are the only stage that feed on prey, thus ideally the supplemental food should result in high larval survival but a low developmental rate. Juvenile survival and developmental time of lacewing larvae were measured on various food items, either alone or mixed with mealybugs. Mealybugs were a suboptimal prey: up to 50 % of the lacewing larvae died before they reached the pupal stage and the developmental time was relatively long when feeding exclusively on mealybugs. Mixing mealybugs with supplemental prey increased larval survival, but also reduced larval developmental time and thereby the period in which the larvae could prey on mealybugs. Moreover, adding eggs of Ephestia kuehniella Zeller, which appeared to be of high quality for lacewings, reduced the consumption of mealybugs by lacewing larvae in the laboratory. The addition of the prey mite Acarus siro (L.) also reduced larval mortality, but did not reduce mealybug predation rates by lacewing larvae. Greenhouse trials showed better mealybug control by lacewing larvae with supplemental prey of low quality (prey mites) rather than alternative prey of high quality (Ephestia eggs). In conclusion, biological control of mealybugs by lacewing larvae was strongly affected by the nutritional quality of the supplemental food source.

Influence of plant, animal and mixed resources on development of the zoophytophagous plant bug Campylomma verbasci (Hemiptera: Miridae)

The mullein bug, Campylomma verbasci (Meyer-Dür) (Hemiptera: Miridae), exploits both plant and animal resources. The aim of this study was (1) to evaluate the quality of different plant, animal and mixed diets (i.e. plant material or prey from the overwintering host, the summer host or the laboratory rearing) for the development and survival of mullein bug, and (2) to evaluate if the suitability of the resource changes according to the nymphal instar of C. verbasci. Mullein bug nymphs were reared individually in Petri dishes containing different diets and observed daily until reaching adulthood or dying. The rearing diet (living potato aphids + potato leaf + Ephestia eggs + apple pollen) was a high-quality diet. The medium-quality diets were apple fruit + apple pollen, Ephestia eggs and Sitotroga eggs. The low-quality diets included mullein leaf, frozen aphids, living aphids + potato leaf and apple fruit + living aphids + potato leaf. Finally, the inappropriate diets (when no nymphs reached adulthood) were agar gel, apple fruit, apple pollen, apple leaf, potato leaf, frozen spider mites and frozen conspecifics. When comparing the value of the diets for different instars, living aphids + potato leaf was a high-quality diet for third instar. Apple pollen and frozen conspecifics were low-quality diets for third instar. ‘Red Delicious’ fruit was a high-quality diet for fifth instar and low-quality for third instar. ‘Honeycrisp’ fruit constituted an inappropriate diet whatever the instar. Thus, a whole mixed diet maximises development and survival of C. verbasci nymphs.

Supplemental food that supports both predator and pest: a risk for biological control?

Supplemental food sources to support natural enemies in crops are increasingly being tested and used. This is particularly interesting for generalist predators that can reproduce on these food sources. However, a potential risk for pest control could occur when herbivores also benefit from supplemental food sources. In order to optimize biological control, it may be important to select food sources that support predator populations more than herbivore populations. In this study we evaluated the nutritional quality of four types of supplemental food for the generalist predatory mites Amblyseius swirskii Athias-Henriot and Amblydromalus (Typhlodromalus) limonicus (Garman and McGregor), both important thrips predators, and for the herbivore western flower thrips Frankliniella occidentalis Pergande, by assessing oviposition rates. These tests showed that application of corn pollen, cattail pollen or sterilized eggs of Ephestia kuehniella Zeller to chrysanthemum leaves resulted in three times higher oviposition rates of thrips compared to leaves without additional food. None of the tested food sources promoted predatory mites or western flower thrips exclusively. Decapsulated cysts of Artemia franciscana Kellogg were not suitable, whereas cattail pollen was very suitable for both predatory mites and western flower thrips. In addition, we found that the rate of thrips predation by A. swirskii can be reduced by 50 %, when pollen is present. Nevertheless, application of pollen or Ephestia eggs to a chrysanthemum crop still strongly enhanced the biological control of thrips with A. swirskii, both at low and high release densities of predatory mites through the strong numerical response of the predators. Despite these positive results, application in a crop should be approached with caution, as the results may strongly depend on the initial predator-prey ratio, the nutritional quality of the supplemental food source, the species of predatory mites, the distribution of the food in the crop and the type of crop.

A case of ecological specialization in ladybirds:Iberorhyzobius rondensis(Coleoptera: Coccinellidae), potential biocontrol agent ofMatsucoccus feytaudi(Hemiptera: Matsucoccidae)

Specialization is an important attribute of a biological control agent. The maritime pine bast scale, Matsucoccus feytaudi Ducasse (Hemiptera Matsucoccidae), is an invasive species in Southeast France and the North of Italy. Iberorhyzobius rondensis Eizaguirre (Coleoptera: Coccinellidae), is a recently described ladybird species. Both adults and larvae are predaceous, feeding on egg masses of M. feytaudi, and are strongly attracted to M. feytaudi's sex pheromone. To evaluate the potential of I. rondensis as a biocontrol agent of the scale, we studied its niche breadth and prey range with emphasis on pine forests and hemipterans as tested prey. In this study, I. rondensis was found to achieve complete development only when fed on M. feytaudi egg masses (92.9% survival) and an artificial prey: eggs of Ephestia kuehniella Zeller (27.6% survival). From the 2nd instar onwards, complete development could be achieved using other prey species, although larvae had significantly higher mortality and slower development. In choice tests, M. feytaudi was the preferred prey. Surveys of the ladybird populations in the Iberian Peninsula revealed that it was found exclusively on Pinus pinaster Aiton, the sole host of M. feytaudi. The unusual specialization of I. rondensis, among other predaceous ladybirds, makes it an appropriate candidate for classical biological control of M. feytaudi.

Maternal effects shape dynamic trajectories of reproductive allocation in the ladybirdColeomegilla maculata

We followed lifetime trajectories of reproductive allocation in Coleomegilla maculata females of three different size classes produced by rearing beetles on three different daily larval feeding regimes (30 min, 6 h or ad libitum access to eggs of Ephestia kuehniella). We hypothesized that small females would produce fewer and smaller eggs than larger females and that reproductive effort would decline with female age. Females were mated with a male from the same treatment and then isolated with ad libitum food for their entire adult lives. Egg size increased over time in all treatments; small females started off laying the smallest eggs, but increased egg size more rapidly than larger females, until all treatments converged on a similar egg size around the 20th day of oviposition. Large females realized a larger proportion of their fecundity early in life, but smaller females increased daily fecundity over time. Reproductive effort (egg mass/body mass) did not decline over 30 oviposition days; it remained constant in large females, but increased among small and medium females, suggesting gradual compensation for larval food deprivation. An increase in egg size with maternal age may be an adaptive strategy to maximize fitness on ephemeral patches of aphid prey, assuming females reproduce in a single aphid outbreak and that offspring produced later in the aphid cycle experience greater competition and risk of mortality compared to those produced earlier. We demonstrate for the first time in Coleoptera that dynamic changes in both egg size and number occur as a function of female age and illustrate that such changes are constrained by larval feeding histories via their effects on maternal body size.

Development and Survival of Orius insidiosus (Say) Nymphs on Encapsulated Bee Pollen-Based Diet in a Tier-I Toxicity Assay

The insidious flower bug, Orius insidiosus (Say) (Heteroptera: Anthocoridae) is an important surrogate species for assessing potential effects of plant-incorporated protectants (PIPs) on nontarget heterotrophic predators. In this study, a continuous dietary exposure system was optimized by assessing the effect of diet composition and age on the survival and development of nymphs of O. insidiosus. Greater than 85% control survival and an acceptable rate of development from nymph hatching to adult was achieved using 5-d-old nymphs at test initiation and a bee pollen-based diet supplemented with 25% Ephestia eggs. There was an unacceptable level of mortality (>40%) and/or a significantly prolonged development time when nymphs were <5 d old at test initiation. When 5-d-old nymphs were fed a bee pollen diet containing 25% Ephestia eggs and 100 μg/g potassium arsenate, time-dependent mortality was observed with a median lethal time (LT50) of 4.4 d and 100% mortality was observed after 10 d of feeding, indicating the effectiveness of the test system to detect adverse effects by dietary exposure. It is recommended that well-defined 5-d-old nymphs and an encapsulated bee pollen-based diet containing 25% ground Ephestia eggs be used in a Tier-I dietary feeding exposure assay for detecting potential effects of PIPs on O. insidiosus nymphs.

Induction of reproductive diapause in Hippodamia convergens (Coleoptera: Coccinellidae) hinges on prey quality and availability

In the High Plains of western Kansas, USA, the convergent lady beetle Hippodamia convergens Guerin completes a spring generation feeding on cereal aphids in winter wheat before leaving fields in large numbers around the time of harvest. In late May, large aggregations of coccinellids form on wild sunflowers, Helianthus annuus, and certain other weeds, that appear to serve as important sources of water absorption for the beetles, and other beneficial insects, during the dry prairie summer. Adult beetles were collected from sunflower plants and held in four treatments: (1) access to water only, (2) access to sunflower stalks only, (3) eggs of Ephestia kuehniella provided ad libitum + water and, (4) greenbug, Schizaphis graminum Rondani provided ad libitum. Most females fed greenbug matured eggs in less than a week and only a few entered reproductive diapause. In contrast, more than half of the females fed Ephestia eggs, an inferior diet, entered reproductive diapause, and those that matured eggs required an average of almost three weeks to do so. Time to 50% mortality was 7 days for beetles receiving only water, and 12 days for those receiving only sunflower stalks, whereupon all survivors were fed greenbug. Even after feeding on greenbugs for a month, less than half of the surviving females in these two treatments produced eggs. We conclude that reproductive diapause is an important adaptation for improving H. convergens survival during summer when aphids are scarce, although females will forgo diapause if they have con- tinuous access to high quality prey.

Influence of diet on life table parameters of Iphiseius degenerans (Acari: Phytoseiidae)

Abstract. Studies on the reproduction, longevity and life table parameters of Iphiseius degenerans (Berlese) were carried out under laboratory conditions of 25 +/- 1 degree C, 75 +/- 5% RH and 16L:8D h. As food sources for the predatory mite, Ricinus communis L. pollen, all stages of the spider mite Tetrranchus urticae Koch, Frankliniella occidentalis (Pergande) larvae, and Ephestia kuehniella Zeller eggs were selected. All diets were accepted as food by the adult mites. Female longevity ranged from 29.5 to 42.4 days, the highest value was recorded on a diet of Ephestia eggs. The highest percentage of females escaping the experimental arena was observed on the diet consisting of thrips larvae. The highest oviposition rate (1.9 eggs/female.day) was recorded when the predator was fed on spider mites on an artificial substrate. For other diets, oviposition rates ranged from 1.0 to 1.3 eggs/female.day. The intrinsic rate of natural increase (r(m)) of I. degenerans varied between 0.015 and 0.142 females/female x day. The diet consisting of castor bean pollen resulted in the highest population growth whereas the diet on spider mites brushed off onto a bean leaf arena resulted in the slowest population growth. This can be explained by the inability of the predator to cope with the webbing of T. urticae, and the high escape rate of the progeny when reared on spider mites. The percentage of females in the offspring ranged from 40 to 73%.