Predatory Midge Research Articles

Prey-induced vertical migration in Chaoborus larvae under different predator and light regimes

For freshwater prey like Daphnia and larvae of Chaoborus, it is well documented that they adjust their residence depth in the water column in response to predator kairomones in order to decrease encounter probability with the respective predator. Despite the importance of infochemicals in predator–prey interactions, it has not been tested if predators adjust their residence depth in response to infochemicals released by prey. Here, we use an indoor system with a stratified water column and show that the predatory phantom midge Chaoborus prefers strata with Daphnia incubation water over strata with control water. Further, the chemically mediated effect of a top predator (fish) on this system was shown to be light dependent with Chaoborus avoiding prey-conditioned water when it also contained fish kairomone in brighter surface water, but not in deeper and thus darker water layers. The foraging kairomone released by Daphnia can be extracted from incubation water via C18-based solid-phase extraction. These results add another dimension to the steering role of infochemicals in predator–prey interactions in zooplankton.

An annotated checklist of scale insects (Hemiptera: Coccoidea) of Saint Lucia, Lesser Antilles.

An annotated list of 83 scale insect species (Hemiptera: Sterorrhyncha: Coccoidea) recorded from Saint Lucia is presented, based on data gathered from UK quarantine interceptions, samples collected in an urban coastal habitat in the North West of the Island in 2013, and published records. Thirty-three species (40%) are recorded for the first time for the country, including Dysmicoccus joannesiae (Costa Lima), a South American mealybug, and Poliaspoides formosana (Takahashi), an Asian armoured scale insect pest of bamboo, which are new for the Caribbean region. The economic, environmental and social impacts caused by introduced exotic species of scale insect are discussed. Two predatory midges Diadiplosis ?coccidivora (Felt) and Diadiplosis multifila(Felt) (Diptera: Cecidomyiidae) are recorded for the first time from Saint Lucia. The latter species was observed causing 90% mortality of a large infestation of passion vine mealybug Planococcus minor (Maskell) on soursop fruit.

Demographic Consequences of Predators on Prey: Trait and Density Mediated Effects on Mosquito Larvae in Containers

Predators may affect prey population growth and community diversity through density mediated lethal and trait mediated non-lethal effects that influence phenotypic traits of prey. We tested experimentally the roles of thinning the density of prey (lethality) in the absence of predator cues and density and trait mediated effects (lethality + intimidation) of predatory midge Corethrella appendiculata on competing native and invasive mosquito prey. Predator-mediated reductions in prey and density reductions in the absence of C. appendiculata resulted in lower percent survivorship to adulthood and estimates of the finite rate of increase (λ′) for invasive mosquito Aedes albopictus relative to that of controls. In most instances, thinning the density of prey in the absence, but not in the presence, of C. appendiculata cues resulted in lower survivorship to adulthood and λ′ for native mosquito Aedes triseriatus relative to that of controls. Together, these results suggested trait mediated effects of C. appendiculata specific to each species of mosquito prey. Release from intraspecific competition attributable to density reductions in the absence, but not in the presence, of C. appendiculata enhanced growth and lengthened adult lifespan relative to that of controls for A. albopictus but not A. triseriatus. These results show the importance of predator-mediated density and trait mediated effects on phenotypic traits and populations of invasive and native mosquitoes. Species-specific differences in the phenotypic responses of prey may be due, in part, to longer evolutionary history of C. appendiculata with A. triseriatus than A. albopictus.

Biological control of aphids in the presence of thrips and their enemies

Generalist predators are often used in biological control programs, although they can be detrimental for pest control through interference with other natural enemies. Here, we assess the effects of generalist natural enemies on the control of two major pest species in sweet pepper: the green peach aphid Myzus persicae (Sulzer) and the western flower thrips Frankliniella occidentalis (Pergande). In greenhouses, two commonly used specialist natural enemies of aphids, the parasitoid Aphidius colemani Viereck and the predatory midge Aphidoletes aphidimyza (Rondani), were released together with either Neoseiulus cucumeris Oudemans, a predator of thrips and a hyperpredator of A. aphidimyza, or Orius majusculus (Reuter), a predator of thrips and aphids and intraguild predator of both specialist natural enemies. The combined use of O. majusculus, predatory midges and parasitoids clearly enhanced the suppression of aphids and consequently decreased the number of honeydew-contaminated fruits. Although intraguild predation by O. majusculus on predatory midges and parasitoids will have affected control of aphids negatively, this was apparently offset by the consumption of aphids by O. majusculus. In contrast, the hyperpredator N. cucumeris does not prey upon aphids, but seemed to release aphids from control by consuming eggs of the midge. Both N. cucumeris and O. majusculus did not affect rates of aphid parasitism by A. colemani. Thrips were also controlled effectively by O. majusculus. A laboratory experiment showed that adult predatory bugs feed on thrips as well as aphids and have no clear preference. Thus, the presence of thrips probably promoted the establishment of the predatory bugs and thereby the control of aphids. Our study shows that intraguild predation, which is potentially negative for biological control, may be more than compensated by positive effects of generalist predators, such as the control of multiple pests, and the establishment of natural enemies prior to pest invasions. Future work on biological control should focus on the impact of species interactions in communities of herbivorous arthropods and their enemies.

Prey Abundance, Intraguild Predators, Ants and the Optimal Egg-laying Strategy of a Furtive Predator

Larval performance can have a great influence on female oviposition choice, especially in insects where the newly hatched offspring are unable to move any great distance to find an appropriate food source. For furtive predators, like the predatory midge Aphidoletes aphidimyza which preys on aphids while simultaneously residing and remaining undetected within their colonies, oviposition behaviour is crucial because these slow moving offspring are restrained to their natal colony. Here we develop a new model for predicting the optimum number of eggs that a furtive predator should lay in an aphid colony, based on: (1) the number of available prey (aphids); (2) the protection from predation conferred by “hiding” in the colony and (3) the effects of interspecific and intraspecific competition. We also explore the effect of aphid attendance by ants on oviposition behavior. We compare model predictions with empirical field observations of the clutch sizes of A. aphidimyza in apple orchards. The simplest of the four models best fits the observed data and provides the first field evidence that a furtive predator adjusts its clutch size as a function of prey density. The slope of the relationship between clutch size and aphid number is quite close to that predicted by our models suggesting that intra-clutch competition is the main factor governing furtive aphid midge oviposition choice.

BIOLOGICAL CONTROL OF APHIDS BY THE PREDATORY MIDGE APHIDOLETES APHIDIMYZA IN THE PRESENCE OF INTRAGUILD PREDATORY BUGS AND THRIPS

BIOLOGICAL CONTROL OF APHIDS BY THE PREDATORY MIDGE APHIDOLETES APHIDIMYZA IN THE PRESENCE OF INTRAGUILD PREDATORY BUGS AND THRIPS

Trait‐mediated effects of predation across life‐history stages in container mosquitoes

1. It was determined if the predatory midgeCorethrella appendiculataGrabham imposes a fitness cost in a native mosquito,Ochlerotatus triseriatusSay, and an invasive mosquito,Aedes albopictusSkuse. The hypothesis that decreased activity of immature prey in the presence of predator cues is associated with life history costs through all life cycle stages was tested.2. In experiment 1, individual larvae ofO. triseriatusorA. albopictuswere raised in the presence or absence of predation cues at two resource levels. Prey were video recorded to detect behavioural responses and to measure development time, size at emergence, and adult longevity. In experiment 2, prey populations were reared in similar environments and the frequency of predator cue additions was varied.3. OnlyO. triseriatusreduced its activity in the presence of predation cues. Predation cues were associated with longer immature development times and shorter adult life spans inO. triseriatus,whereas inA. albopictus, the cues were associated with a larger size of emerging adults.4. In the present study, it was found that behavioural modifications during the larval stage can affect mosquitoes through multiple stages of their complex life cycle. The species‐specific behavioural differences are probably attributable to the longer evolutionary historyO. triseriatushas with predators, relative to the invasiveA. albopictus.

Hyperpredation by generalist predatory mites disrupts biological control of aphids by the aphidophagous gall midge Aphidoletes aphidimyza

Biological control of different species of pest with various species of generalist predators can potentially disrupt the control of pests through predator-predator interactions. We evaluate the impact of three species of generalist predatory mites on the biological control of green peach aphids, Myzus persicae (Sulzer) with the aphidophagous gall midge Aphidoletes aphidimyza (Rondani). The predatory mites tested were Neoseiulus cucumeris (Oudemans), Iphiseius degenerans (Berlese) and Amblyseius swirskii Athias–Henriot, which are all commonly used for pest control in greenhouse sweet pepper. All three species of predatory mites were found to feed on eggs of A. aphidimyza, even in the presence of abundant sweet pepper pollen, an alternative food source for the predatory mites. In a greenhouse experiment on sweet pepper, all three predators significantly reduced population densities of A. aphidimyza, but aphid densities only increased significantly in the presence of A. swirskii when compared to the treatment with A. aphidimyza only. This stronger effect of A. swirskii can be explained by the higher population densities that this predator reached on sweet pepper plants compared to the other two predator species. An additional experiment showed that female predatory midges do not avoid oviposition sites with the predator A. swirskii. On the contrary, they even deposited more eggs on plants with predatory mites than on plants without. Hence, this study shows that disruption of aphid control by predatory mites is a realistic scenario in sweet pepper, and needs to be considered when optimizing biological control strategies.

Invertebrate Predators and Preservation Time Lags in Zooplankton Samples: Effects on the Estimates of Prey Abundance and Size

ABSTRACT The effects of predatory phantom midge (Chaoborus flavicans) larvae on the density and size estimates of crustacean zooplankton with different time lags between sampling and sample preservation were studied. Chaoborid larvae may easily be included in zooplankton samples, especially if samples are taken with net hauls. Five larvae included in a sample had a significant negative effect on the density estimate of daphnids, cyclopoid and calanoid copepods, and cyclopoid nauplii. When chaoborids were included in the samples, a three-hour preservation lag caused a >5% underestimation of population density estimate of cyclopoids and a six hour lag resulted in a 10% error. In field studies, chaoborids usually prefer small cladocerans such as bosminids as prey, but in the restricted space of the sample containers escape ability of cyclopoids was diminished. As a result, cyclopoids were the main prey of chaoborids. Chaoborids had no effect on the mean individual size of any of the taxa, but in the reference samples the mean size of daphnids and calanoids was reduced. This, as well as the reduced density of cyclopid nauplii in the reference samples, was attributed to predation by cyclopoids. The results emphasized that zooplankton samples should be preserved immediately after the sample haul.

Your worst enemy could be your best friend: predator contributions to invasion resistance and persistence of natives

Native predators are postulated to have an important role in biotic resistance of communities to invasion and community resilience. Effects of predators can be complex, and mechanisms by which predators affect invasion success and impact are understood for only a few well-studied communities. We tested experimentally whether a native predator limits an invasive species' success and impact on a native competitor for a community of aquatic insect larvae in water-filled containers. The native mosquito Aedes triseriatus alone had no significant effect on abundance of the invasive mosquito Aedes albopictus. The native predatory midge Corethrella appendiculata, at low or high density, significantly reduced A. albopictus abundance. This effect was not caused by trait-mediated oviposition avoidance of containers with predators, but instead was a density-mediated effect caused by predator-induced mortality. The presence of this predator significantly reduced survivorship of the native species, but high predator density also significantly increased development rate of the native species when the invader was present, consistent with predator-mediated release from interspecific competition with the invader. Thus, a native predator can indirectly benefit its native prey when a superior competitor invades. This shows the importance of native predators as a component of biodiversity for both biotic resistance to invasion and resilience of a community perturbed by successful invasion.

Stage‐dependent predation on competitors: consequences for the outcome of a mosquito invasion

1. Predator-mediated coexistence occurs when predation allows competitors to coexist, due to preferential consumption of a superior competitor relative to an inferior competitor. Differences between the native treehole mosquito (Aedes triseriatus) and the co-occurring Asian tiger mosquito (Aedes albopictus) in anti-predatory larval behaviours account, in part, for the greater vulnerability of this invasive species to native predatory midge (Corethrella appendiculata). We test the hypothesis that stage-dependent differences in the sizes of A. albopictus and A. triseriatus larvae, relative to the size-limited C. appendiculata, contribute to differential consumption and the likelihood of predator-mediated coexistence of these competitors. 2. In all instars, larvae of A. triseriatus were larger than A. albopictus of the same stage. Third and fourth instar C. appendiculata selectively consumed late-stage A. albopictus in preference to same-stage A. triseriatus. Small, early-stage prey larvae did not differ in vulnerability to predation, but large, late-stage larvae differed significantly in vulnerability to predation, probably owing to size-limited predation by fourth instar C. appendiculata. This effect was less pronounced for third instar C. appendiculata. 3. Prey size, in conjunction with anti-predatory behavioural responses, alters the probability of predator-mediated coexistence. A stage-structured predation model showed that equally vulnerable early stages reduce the range of environmental conditions (productivities) in which predator-mediated coexistence is possible, increasing the likelihood of both competitive exclusion of the resident species or failure of the invasive to establish. These results underscore the importance of stage-dependent interspecific differences in predator-prey interactions for determining how predators may affect community composition.

No Evolutionary Response to Four Generations of Laboratory Selection on Antipredator Behavior of <I>Aedes albopictus</I>: Potential Implications for Biotic Resistance to Invasion

Aedes albopictus (Skuse) is an invasive container-dwelling mosquito and an important disease vector that co-occurs with the native mosquito, Aedes triseriatus (Say), and the predatory midge, Corethrella appendiculata (Grabham). Larval Ae. triseriatus show significantly greater antipredatory responses when compared to larval Ae. albopictus in the presence of predation cues from C. appendiculata. The potential for evolution of antipredatory behavioral responses to C. appendiculata in Ae. albopictus is unknown. We used a controlled laboratory selection experiment to test whether Ae. albopictus could evolve antipredatory behavioral responses to C. appendiculata predation. We subjected replicate Ae. albopictus populations to four generations of predation by C. appendiculata or a predator-free control treatment and compared the behavior and life history of Ae. albopictus in the two treatments in each generation. There were no differences in Ae. albopictus behavioral responses between predation and control lines in any of the four generations. There was also no evidence of differences in life histories between predation and control lines. Ae. albopictus is superior as a competitor compared with Ae. triseriatus, which it has replaced in areas where C. appendiculata are rare. Our results suggest limited potential for Ae. albopictus to evolve stronger antipredatory behavioral responses to C. appendiculata predation and imply that C. appendiculata will continue to act as an impediment to invasion by Ae. albopictus and replacement of Ae. triseriatus and to promote coexistence of these competitors.

Surplus Killing by Predatory Larvae of Corethrella appendiculata: Prepupal Timing and Site-Specific Attack on Mosquito Prey

Surplus or 'wasteful' killing of uneaten prey has been documented in the fourth larval instar of various species of the mosquito genus Toxorhynchites that occur in treeholes and other phytotelmata. Here we document surplus killing by the predatory midge Corethrella appendiculata, which in Florida cohabits treeholes and artificial containers with larvae of Toxorhynchites rutilus. Provided with a surfeit of larval mosquito prey, surplus killing was observed only in the fourth instar of C. appendiculata, peaking in intensity in the final 24 h prior to pupation, as observed for Toxorhynchites spp. Attack sites identified from videotaped encounters with mosquito prey were divided among head, thorax, abdomen, and siphon. Consumed mosquito larvae (n = 70) were attacked primarily on the head (46%) or siphon (34%), but surplus-killed prey (n = 30) were attacked predominantly on the thorax (83%). Despite its independent evolution among different insect species in aquatic container habitats, the functional significance of prepupal surplus killing remains unclear.

Quality assessment of selected commercially available whitefly and aphid biological control agents in the United States.

This study assessed the quality of three commercially available natural enemies used for pest management in greenhouses: the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae), the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae), and the aphid predatory midge Aphidoletes aphidimlyza (Rondani) (Diptera: Cecidomyiidae). Shipment packaging was consistent for all natural enemies. However, there was high variability in delivery punctuality, product cost, and product information provided by each of the six selected companies. Product quantity, percentage of emergence upon arrival, percentage of total emergence, percentage of females, and percentage of flying insects were assessed using International Organization for Biological Control (IOBC) recommended procedures. The parameters with greatest variability between companies were percentage of emergence upon arrival (0.9-10.5%) and percentage of flying insects (35.4-85.0%) for E. formnosa; product quantity (623.3-833.8 aphid mummies), percentage of emergence upon arrival (6.1-41.2%) and percentage of females (51.1-54.8%) for A. colemani; and percentage of emergence upon arrival (0.0-7.7%) and percentage of females (54.6-76.2%) for A. aphlidimyza. Results are discussed in terms of the value to consumers and compared with IOBC standards.

Low‐temperature storage and cold hardiness in two populations of the predatory midge Aphidoletes aphidimyza, differing in diapause intensity

Abstract. The potential for medium‐time, low‐temperature storage was compared in diapausing larvae of two populations of Aphidoletes aphidimyza, a predatory midge used to control aphids in greenhouses. During 4 months of storage, no statistical decrease of survival rate (c. 75%) was observed in the population Palamos (field collected). However, a significant decrease (below 50%) was recorded in the population Biobest (commercial, selected for the best performance in greenhouses). Measuring physiological parameters related to the rate of diapause development revealed that the larvae of the population Palamos (in contrast to Biobest) showed a significant metabolic suppression even at the relatively high temperature of 17°C, a slower rate of glycogen depletion during storage at 3°C and a longer duration of diapause development (a higher intensity of diapause, collectively). A higher capacity for survival at subzero temperatures (cold hardiness), in either the supercooled or frozen state, was also found in the Palamos population. It is suggested that the higher survival at low‐temperature storage might be linked directly to the higher diapause intensity. It remains unclear, however, whether and how the performance during low‐temperature storage is linked to the capacity for cold hardiness.

Sex Ratios of Commercially Reared Biological Control Agents

We purchased samples of 27 parasitoids, six coccinellid beetles, and the predatory midge Aphidoletes aphidimyza (Rondani) from commercial insectaries and scored the sex ratios from groups of approximately 200 individuals from each of these samples. Parasitoid sex ratios ranged from all female to 0.77 (proportion males), and none of the predator sex ratios differed significantly from 0.5. Among the parasitoids, we found no significant effect of taxonomic affiliation (family, superfamily) or life history (gregarious vs solitary development) on the sex ratio. The pteromalid parasitoids Muscidifurax raptorellus (Kogan and Legner), M. zaraptor (Kogan and Legner), and Nasonia vitripennis (Walker) and the eulophid Diglyphus isaea (Walker) all had significantly male-biased sex ratios, and an additional five species that did not have male-biased sex ratios had sex ratios that had a higher proportion of males than reported in the literature. These were Cotesia plutellae Kurdjumov (Braconidae), Dacnusa sibirica Telenga (Braconidae), Eretmocerus nr. californicus Howard (Aphelinidae), Trichogramma brassicae Bezdenko (Trichogrammatidae), and Pediobius foveolatus (Crawford) (Eulophidae). This suggests that it may be possible to increase the proportion of females produced by these species under conditions of commercial rearing. In the rest of the species studied (74% of species purchased), sex ratios either conformed to most published reports or had a higher proportion of females. We discuss the sex ratios of each species or group of species separately and review potential explanations for the sex ratios that we found, as well as implications of the results for mass rearing.

THE FUNCTIONAL RESPONSE AND PREY PREFERENCE OF FELTIELLA ACARISUGA (VALLOT) (DIPTERA: CECIDOMYIIDAE) FOR TWO OF ITS PREY: MALE AND FEMALE TWOSPOTTED SPIDER MITES, TETRANYCHUS URTICAE KOCH (ACARI: TETRANYCHIIDAE)

AbstractThe preference of the predatory midge, Feltiella acarisuga (Vallot), for adult male and female twospotted spider mite, Tetranychus urticae Koch, was examined using functional response models. The midge exhibited a type-II functional response to each prey. Handling time was estimated to be much higher for the female mites than for the males (1.52 vs. 0.40 h). Estimated instantaneous search rates for the female and male mites were similar (1.32 vs. 1.28). A preference index of 1.03 was calculated using the ratio of the instantaneous search rates. Feltiella acarisuga was found to exhibit no preference for either female or male mites; when both prey were present in equal numbers, midge larvae killed as many females as males.

Direct distributional response in Daphnia pulex to a predator kairomone

The hypothesis that zooplankton are capable of direct and differentiated behavioural responses to different biotic factors was tested. A multichamber flow-through technique enabled pre- determined food levels of the green alga Scenedesmus acutus to be maintained constant throughout the experiments. By adding water from a culture of fourth instar Chaoborus flavicans larvae to one of the end chambers, a concentration gradient of the chemical substance was established across the par- allel chambers. Evidence is presented for a direct avoidance response in the water flea Daphnia pulex to a substance released by the predatory midge C.flavicans. This response occurs in the absence of visual cues and is independent of food availability. Finally, the results indicate that swarming in D.pulex may occur in the absence of both light and predator scent, but is influenced by food concentrations.

Laboratory pesticide screening method for the aphid predatory midgeAphidoletes aphidimyza(Rondani) (Diptera: Cecidomyiidae)

A laboratory pesticide screening method is described for the aphid predatory midge Aphidoletes aphidimyza. Four acaricides, 10 fungicides, 11 insecticides and one herbicide, all of which are in common usage, were evaluated against both the adult and larval stages of the predator. The acaricide dienochlor, the fungicides benomyl, bupirimate, chlorothalonil, iprodione and hexaconazole, the herbicide tralkoxydim and the insecticides Bacillus thuringiensis and diflubenzuron were all safe to both adult and larval A. aphidimyza. Adults were more susceptible to the pesticides than larvae. Pesticide was exposed to adults as a residue on glass plates and to larvae on a leaf section mounted on agar. The leaf material remained healthy and supported host aphids for several days without deteriorating. The method and apparatus have potential for use with many other pests and beneficial organisms required to be caged for several days on detached leaf material.

Cold Storage of the Predatory Midge Aphidoletes aphidimyza (Diptera: Cecidomyiidae)

Long-term cold storage of a commercial biological control agent for aphids, the predatory midge Aphidoletes aphidimyza (Rondani), was investigated as a way to reduce rearing costs and to preserve genetically important lines. Prolonged cold storage of last instars in cocoons at temperatures of 1-11 degree C in total darkness was sufficient as an environmental cue to induce diapause, even though larvae had been reared under conditions that would not induce diapause. Mortality and emergence patterns of midges diapausing in response to cold storage did not differ from those of larvae reared under diapause-inducing conditions (8-h day at 21 degree C, 16-h night at 15 or 18 degree C) before cold storage. For commercial application, cold storage regimes with lowest mortality (< 10%) and highest percentage of emergence in the first 4 d of the adult emergence period were: 2 wk at 10-11 degree C, up to 4 wk at 5 degree C, and up to 2 mo at 1 degree C after acclimation for 10 d at 5 degree C. Larvae stored at 5 degree C survived 8 mo with <9%, mortality, and fecundity of females was not significantly different than in unstored controls. These effects are useful for preserving A. aphidimyza lines for future research. However, the adult emergence period was too protracted for commercial application. Methods for synchronizing emergence (including cold chill at 1 degree C and 2-4-d heat shock at 33 degree C) were tested, but only desiccation for a week, followed by remoistening, gave promising results.