Important Predators Research Articles

Toxicity of imidacloprid, fenpropathrin, and dimethoate to Ceraeochrysa cubana (Neuroptera: Chrysopidae) through different exposure routes

Ceraeochrysa cubana (Hagen) (Neuroptera: Chrysopidae) is an important predator with potential use to control various agricultural pests, including Diaphorina citri Kuwayama (Hemiptera: Liviidae). However, the indiscriminate use of insecticides may affect the performance of this lacewing, reducing its efficiency as a natural enemy. The goal of this study was to evaluate the lethal effect of imidacloprid, fenpropathrin, and dimethoate on C. cubana using different routes of exposure. Bioassays of topical, residual, ingestion, and residual + ingestion (simultaneous exposure) of the active ingredients on the lacewings were performed. The tolerance ratio (TR) was calculated from the lowest LC50 observed. In addition to the lethal effect, we also studied the repellent effect of imidacloprid and fenpropathrin on first instar larva of C. cubana when Ephestia kuehniella Zeller (Lepidoptera, Pyralidae) eggs were treated with those insecticides. In the toxicity bioassay, the residual exposure of dimethoate was the most lethal (lower value of LC50), followed by residual + ingestion exposure of dimethoate and fenpropathrin. With topical exposure, insecticides had similar toxicity and TR was between 20.76 and 23.61-fold. Imidacloprid was not toxic via ingestion and residual exposure; consequently, we did not estimate LC50 in those cases. Ephestia kuehniella eggs treated with imidacloprid did not repel C. cubana larvae while those treated with fenpropathrin had a repellent effect. Dimethoate was toxic to C. cubana and it should be used with caution while imidacloprid has a lower lethal effect via residual and ingestion exposure and it does not have a repellent effect on C. cubana.

A new species of emTyphlodromus/em (Anthoseius) De Leon and redescription of emT. (A.)/em emmontanus/em Chant amp; Yoshida-Shaul from Russia.

Typhlodromus (Anthoseius) tetraporus sp. nov., collected on grasses in Crimea, is proposed as a new species for science. The new species can be separated from all known species of Typhlodromus (Anthoseius) by the combination of following characters; peritreme extending almost to level of setae j1, four pairs of solenostomes on dorsal shield, two pairs of setae on sternal shield, a sclerotised v-shaped plate posterior to sternal shield, four pairs of pre-anal setae, a pair of small rounded pre-anal solenostomes, differentiated and larger atrium of spermatheca and eight setae on genu II. In addition, T. (A.) montanus Chant Yoshida-Shaul (Acari: Phytoseiidae), a species only known based on its original description from Canada is reported for the first time in Russia. The new record is redescribed and illustrated based on female specimens collected from Prunus padus L. (Rosaceae) where it was associated with eriophyid mites in Pereval Seminskiy, Altai Republic. This species may be an important predator as a potential biological control agent of eriophyid mites.

Trade-off between predation risk and behavioural thermoregulation drives resting behaviour in a cold-adapted mesocarnivore

Behavioural trade-offs arise when animals must decide to engage in one behaviour at the expense of another, potentially to the animal's detriment. Here, we investigate the existence of such a trade-off by exploring the relative influence of two important behavioural processes, thermoregulation and predation avoidance, on resting behaviour in a cold-adapted mesocarnivore, the wolverine, Gulo gulo. Using animal-borne biologgers, we evaluate the hypothesis that wolverine resting behaviour in both subnivean cavities and on surface snow beds is influenced by a combination of ambient weather conditions and predation risk. Specifically, we posit that although resting on the snow surface is more thermally advantageous in certain weather conditions, it is traded off against heightened predation risk. In support of the importance of thermoregulation, we find that wolverines rest almost exclusively in subnivean cavities at very low temperatures and low levels of solar radiation, and rest almost exclusively on the snow surface at higher temperatures and higher levels of solar radiation. In support of the importance of predation avoidance, we find that wolverines select more topographically concealed sites and are more vigilant while resting on the snow surface. We also find that wolverines are more vigilant at topographically exposed resting sites than at concealed sites. Together, these lines of evidence suggest that wolverines trade security from predators for thermal advantage at warmer ambient temperatures and higher solar radiation levels during winter, but that this trade-off is not necessary at lower temperatures when wolverines preferentially use subnivean cavities to simultaneously meet both demands. Parsing such contextually dependent trade-offs is important to understanding species' habitat selection, energy management and survival.

Ocean acidification but not elevated spring warming threatens a European seas predator

Ocean acidification has the potential to negatively affect marine ecosystems by influencing the development and metabolism of key members of food webs. The garfish, Belone belone, is an ecologically important predator in European regional seas and it remains unknown how this species will be impacted by projected changes in climate. We artificially fertilized and reared garfish embryos until hatch at present (400 μatm) and future (1300 μatm) pCO2 levels within three temperature treatments, i.e. two daily warming regimes and one constant high temperature (17 °C). For the two warming treatments, embryos were fertilized at 13 °C and experienced 0.1 or 0.3 °C/day warming. The 0.1 °C/day treatment served as control: 13 °C was the in situ temperature of parental fish in the Southwest Baltic Sea and 0.1 °C/day is the average warming rate experienced by embryos of this population in nature. Survival was drastically reduced at both future pCO2 and at the constant high temperature while the highest survival in any treatment was observed at 0.3 °C/day warming. The proportion of embryos with morphological deformities increased with elevated pCO2 but not temperature. Hatch characteristics and physiological measures such as heart rate and critical thermal ranges, however, were not affected by pCO2 but were influenced by temperature. Our results suggest that garfish in the Baltic Sea will benefit from projected increased rates of spring warming but not the concomitant increase in pCO2. Previous studies on the impacts of ocean acidification on resident fishes in the Baltic Sea indicate that this piscivorous fish is at higher risk compared to its prey which may have broader implications for the future trophodynamic structure and function of the coastal food web.

Aggregation site fidelity and movement patterns of the protected marine predator giant sea bass (Stereolepis gigas)

Giant sea bass (Stereolepis gigas, Polyprionidae) are the largest reef-associated teleost in the northeastern Pacific, considered an important predator in Macrocystis kelp forest and rocky reef ecosystems. Because of the predictability of annual aggregations, giant sea bass (GSB) were fished throughout the twentieth century until they were nearly extirpated from southern California and Baja California, Mexico. To assess population recovery, acoustic telemetry was used to quantify spatiotemporal rhythmicity of GSB aggregations at Santa Catalina Island, California, USA. Thirty-two individuals were tracked for 498 days over two consecutive spawning seasons in 2017–2018 and visual surveys were conducted monthly to estimate aggregation sizes. Aggregation behavior was documented from June–October and spawning most likely occurred at a pinnacle promontory from July–September. GSB exhibited residency to specific sites throughout the year and individuals showed fidelity to suspected spawning aggregation sites during the summer months. Ten (31%) GSB were detected at Santa Catalina Island year-round and 11 (34%) exhibited suspected annual spawning site fidelity. Four individuals (12%) were documented leaving the island during late fall/winter 2017 and returning in spring/early summer 2018, indicating partial seasonal migration and year-round fidelity to specific sites at Santa Catalina Island. This study provides a baseline of spatiotemporal movements and behavioral patterns that can be used to improve our understanding of GSB and enhance management for these and other large-bodied predatory fish species.

Evidence of historical isolation and genetic structuring among broadnose sevengill sharks (Notorynchus cepedianus) from the world’s major oceanic regions

Cosmopolitan marine pelagic species display variable patterns of population connectivity among the world’s major oceans. While this information is crucial for informing management, information is lacking for many ecologically important species, including apex predators. In this study we examine patterns of genetic structure in the broadnose sevengill shark, Notorynchus cepedianus across its global distribution. We estimate patterns of connectivity among broadnose sevengill shark populations from three major oceanic regions (South Atlantic, Oceania and Eastern Pacific) by contrasting mitochondrial and nuclear DNA haplotype frequencies. We also produced time calibrated Bayesian Inference phylogenetic reconstructions to analyses global phylogeographic patterns and estimate divergence times among distinctive shark lineages. Our results demonstrate significant genetic differentiation among oceanic regions (ΦST = 0.9789, P < 0.0001) and a lack of genetic structuring within regions (ΦST = − 0.007; P = 0.479). Time calibrated Bayesian Inference phylogenetic reconstructions indicate that the observed patterns of genetic structure among oceanic regions are historical, with regional populations estimated to have diverged from a common ancestor during the early to mid-Pleistocene. Our results indicate significant genetic structuring and a lack of gene flow among broadnose sevengill shark populations from the South Atlantic, Oceania and Eastern Pacific regions. Evidence of deep lineage divergences coinciding with the early to mid-Pleistocene suggests historical glacial cycling has contributed to the vicariant divergence of broadnose sevengill shark populations from different ocean basins. These finding will help inform global management of broadnose sevengill shark populations, and provides new insights into historical and contemporary evolutionary processes shaping populations of this ecologically important apex predator.

Dietary analysis and mesocosm feeding trials confirm the eastern rock lobster (

Worldwide, lobsters are considered important predators of macroalgae-consuming urchin species, but this has not been tested for Australia’s common lobster, the eastern rock lobster (Sagmariasus verreauxi). We predicted that the abundant urchins, the long-spined urchin (Centrostephanus rodgersii) and the short-spined urchin (Heliocidaris erythrogramma), would form substantial components of lobster diets. To test this hypothesis, we examined 115 lobster stomachs from 9 locations and conducted 14 feeding trials, in which lobsters were offered either urchin species. Dissections revealed various stomach items, with detritus (51%), bivalves (34%), gastropods (28%) and algae (26%) occurring more frequently than urchins (19%). Urchin spines were found in 22 lobsters that ranged in size from 91- to 124-mm carapace length, with all individuals containing H. erythrogramma spines and C. rodgersii spines observed only once. During feeding trials, seven urchins were consumed. Four H. erythrogramma were eaten on Day 1, whereas one was not eaten until Day 11. Two C. rodgersii were eaten on Days 2 and 10. Only three of the six lobsters observed to eat urchins ingested spines. Together, these data show that S. verreauxi is a generalist predator that consumes urchins, although, because urchins could be eaten without ingesting spines, future studies are needed to assess the importance of urchins as dietary items for S. verreauxi.

Insights Into the Establishment of Introduced Species Using Coccinellines (Coleoptera: Coccinellidae) as a Model System

Species introductions occur around the world both inadvertently and deliberately (typically for conservation, agriculture or fisheries). However, not all introduced species become established. Understanding the factors that affect the establishment success of introduced species will help us improve species introductions for biocontrol and conservation purposes. Here we argue that important generalist arthropod predators, the Coccinellini ladybirds (Coleoptera: Coccinellidae), are an ideal taxon for investigating the establishment process of introduced species. Coccinellini are introduced accidently via plant exports, as well as deliberately as biocontrol agents to reduce agricultural pests, and a few have become invasive species. Here, using work from invasive biology and biocontrol systems, we categorize the factors affecting the successful establishment of introduced species. These factors are 1) invasiveness of the species, 2) invasibility of the recipient ecosystem and 3) stochastic events that occur after the introduction. We review how factors such as diet and competition, dispersal ability, propagule population, disturbances and climate change can be studied within these three categories to better predict the establishment success of introduced ladybirds. Our review highlights that our current understanding of the differences between successful and unsuccessful species establishments is limited. To address this, we need direct comparisons of dispersal ability and both interspecific and intraspecific variation in ladybirds. We conclude that studies of ladybirds will help to develop theories that better characterize and predict establishment success and invasive potential.

Impact of Nest Predators on Migratory Woodpigeons Columba palumbus in Central Europe — Breeding Densities and Nesting Success in Urban Versus Natural Habitats

The Woodpigeon Columba palumbus is a species generally increasing in numbers in most of its populations, including the urban population, which, two centuries after its emergence, is still expanding across the European Lowland. New for the species is a tendency to form dense breeding aggregations in suitable urban parks, with a corresponding slower increase in some other towns. This trend was driven by the presence of important nest predators, mostly Hooded Crows Corvus corone. Another factor involved was access to open farmland within the economic range of feeding flights. Nesting success (1st brood) in urban habitats free of important predators was up to 50–77% but it fell to only 3–7% when predators appeared. Consequently, some urban populations of the Woodpigeon went into a phase of decline. In the farmland and secondary woods, the nesting success was also variable, ranging between 12 and 42% for unknown reasons. Safe urban populations produced 4–5 times more offspring per pair per season, yet their expansion was rather slow. Therefore, the urban overproduction may contribute to an increase in the total species abundance, owing to (deduced) overspill of recruits to the poorly reproducing subpopulation in the countryside. Alongside other factors such as amelioration of winter conditions and changes in agriculture, this would contribute to the documented growth of the whole population of the species. The shortage of firm data on the pristine breeding success (from extensive natural forests) remains the main obstacle to better understand the population dynamics of this migratory species.

Lethal and sublethal effects of three insecticides on first instar larvae of green lacewing, Chrysoperla carnea, Stephens

The green lacewing, Chrysoperla carnea, Stephens (Neu.: Chrysopidae) is one of the most important predators for insect pests such as whiteflies, thrips, psyllids and aphids that ignificantly decrease their populations. In the current study, lethal (LC50) and sublethal effects (LC30) of three insecticides; clothianidin, tebufenozide and flupyradifurone on first instar larvae of C. carnea (<one-day old) and their biological characteristics were evaluated using fertility life table method. Bioassays were conducted by contact method with glass petri-dishes (10 cm diameter). All experiments were conducted at controllable conditions of 25 ± 1 C°, 60 ± 5% and a photoperiod 16:8 h (L:D). The results revealed that LC50 for clothianidin, tebufenozide and flupyradifurone were 8.55, 336.12 and 642.02, respectively. Moreover, the life table response experiment shows that the values of rm and R0 due to LC30 for clothianidin, tebufenozide and flupyradifurone were 0.13, 0.13 and 0.15 per day and 95.72, 97.00 and 136.27 offspring, respectively. At the same time, rm and R0 in the control group were 0.15 per day and 143.26 offspring. Furthermore, the highest survival rate of C. carnea was observed in tebufenozide (54 days) but after control treatment, the lowest survival rate was related to clothianidin (46 days). Results reveal that longevity and life span of both sexes in three treatments were different from the control. According to the IOBC-system, comparing the total effects indicated that clothianidin (77.83%) was classified as slightly harmful while tebufenozide (20.43%) and flupyradifurone (12.89%) were categorized as harmless classes. Hence, based on obtained results, it can be concluded that flupyradifurone than clothianidin are harmless while tebufenozide is less hazardous on C. carnea population. We also measured the esterase enzyme activities of the C. carnea as biomarkers of sublethal exposure to insecticides. The results showed that alpha and beta-esterase activity in treated insects with clothianidin and flupyradifurone was increased (compared to the control), while the enzymatic activity was reduced in insects with tebufenozide treatment.

Phylogeography of two marine predators, giant trevally (Caranx ignobilis) and bluefin trevally (Caranx melampygus), across the Indo-Pacific

For economically valuable marine fishes, identifying biogeographic barriers and estimating the extent of gene flow are critical components of fisheries management. We examined the population genetic structure of two commercially important reef-associated predators, the giant trevally ( Caranx ignobilis) and bluefin trevally (Caranx melampygus). We sampled 225 individuals and 32,798 single nucleotide polymorphisms (SNPs) of C. ignobilis, and 74 individuals and 43,299 SNPs of C. melampygus. Analyses of geographic population structure indicate the two species display subtly different phylogeographic patterns. Caranx ignobilis comprises two to three putative populations—one in the Central Pacific, one inhabiting the Western Pacific and Eastern Indian oceans, and one in the Western Indian Ocean—with some restricted gene flow between them. Caranx melampygus shows evidence of restricted gene flow from Hawaii to the West Pacific and Indian oceans, as well as limited genetic connectivity across the Indo- Pacific Barrier. Both species exhibit patterns characteristic of other large, reef-associated predators such as deepwater snappers and the great barracuda. This study contributes to ongoing assessments of the role of the Indo-Pacific Barrier in shaping patterns of phylogeography for large reef-associated fishes. Furthermore, by identifying putative populations of C. ignobilis and C. melampygus in the Central Pacific, our findings serve to improve future management measures for these economically important, data-limited species, particularly in light of historic and contemporary overfishing in Hawaii.

Quantitative molecular detection of larval Atlantic herring (Clupea harengus) in stomach contents of Atlantic mackerel (Scomber scombrus) marks regions of predation pressure

Mortality rates in the early life-history stages of fishes are generally high yet identifying the causes remain unclear. Faltering recruitment rates of Atlantic herring (Clupea harengus) in the Norwegian Sea indicate a need to identify which mortality factors influence larval herring survival. Previous research suggests that increased predation pressure by Atlantic mackerel (Scomber scombrus) may contribute to the disconnect between spawning stock biomass and recruitment. To quantify the contribution of predation pressure by Atlantic mackerel to herring larval mortality, two research cruises were conducted within a probable “hot spot” (67–72° N) for intensified mackerel predation based on particle drift simulations. Mackerel stomach contents were analysed for herring larvae content using droplet digital polymerase chain reaction (ddPCR) with a quantitative molecular detection assay specific for herring. The ddPCR results demonstrate clear predation by mackerel on herring larvae and also suggest that the alternative use of visual examination may give misleading results. Our results show that mackerel should be considered a potentially important predator on herring larvae. The quantitative molecular assay presented here shows great promise as an efficient and specific tool to correctly identify and quantify predation pressure on early life-history stages of fishes.

Soil arthropod species and their abundance in different chili management practices in freshwater swamps of South Sumatra, Indonesia

The chili management practices can influence the predatory arthropod community. This study aimed to identify soil arthropod species and examine their abundance in different chili management practices in freshwater swamps of South Sumatra. The survey was conducted in three types of chili field, first without mulch and synthetic insecticides, and by fertilizing using manure (EF). The Conventional 1 (C-1) used plastic mulch, synthetic fertilizers, and synthetic insecticides. The Conventional 2 (C-2) used insecticides and synthetic fertilizers but without mulch. The total of all soil arthropod species was found in the different chili management practices of 24 species originating from Insecta, Arachnida, and Diplopoda. The highest number of soil arthropod species was found in EF, while the least number was found in C-1. This survey found species of predatory mites (Macrocheles dispar), spiders (Pardosa birmanica), and predatory insects (Coccinella transversalis) and other important predators such as Pheropsophus occipitalis and Pardosa pseudoannulata. The abundance of soil arthropods either predators, herbivores or neutral insects was the highest in EF, while the lowest one was in the C-1. Overall, different chili management practices affected the number of species and abundance of soil arthropods; the environmentally friendly plot has the highest number of species and the largest abundance.

The Relative Potency of some Pesticides against Cotton Leafworm, Spodoptera littoralis (Boisd.) and their Side Effect on the Natural Enemy, Chrysoperla carnea (Stephens)

The cotton leafworm, Spodoptera littoralis (Boisd.) is one of the dangerous economic insects on different crops in Egypt because it causes more damages in crops especially cotton and leafy vegetables. On the other hand, the natural enemy, Chrysoperla carnea (Stephens) is an important predator in all fields because it is able to control many insect pests and mites. In this study, six commercial pesticides (Chlorpyrifos, Alpha-cypermethrin, Methomyl, Abamectin, Biossiana, and Dipel) and two new compounds under the study (Crude extract of Beauveria bassiana metabolites and synthesis compound from Cyanoacetamide derivatives) were tested to determine their toxicity against the 2nd instar larvae of S. littoralis and their side effects against the 2nd instar larvae of C. carnea. All tested compounds had different degrees of toxicity against both tested insects. Based on the values of LC50 , toxicity index and relative potency, Alpha-cypermethrin was the highest toxic pesticide against S. littoralis and C. carnea followed by Methomyl and Chlorpyrifos but Biossiana was the least toxic one. In addition, the toxicity of tested chemical pesticides against C. carnea was more than their toxicity against S. littoralis. While, the toxicity of tested biopesticides against C. carnea was less than their toxicity against S. littoralis. In general, the sensitivity of the predator C. carnea to the tested biopesticides was less in comparison with chemical pesticides. Therefore, this study recommends using biopesticides besides the slight using of chemical pesticides to preserve the natural enemies and environment and achieve the best pest control.

The truth about scats and dogs: Next-generation sequencing and spatial capture–recapture models offer opportunities for conservation monitoring of an endangered social canid

Obtaining accurate population counts of endangered species is central to conservation biology, with implications for gaining ecological insights, informing management strategies, and judicial use of conservation funds. Despite decades of progress in methodological developments in the realm of population ecology, reliable density estimates are unavailable for many species of conservation concern. The dhole (Asiatic wild dog Cuon alpinus) is one such endangered large carnivore found in the tropical forests of south and southeast Asia. Here, we (i) develop next-generation sequencing resources to identify individual dholes from genetic samples, (ii) apply these methods to identify individuals in the wild, from scat (fecal) samples collected through systematic field surveys and (iii) generate reliable estimates of dhole densities in Wayanad Wildlife Sanctuary (Western Ghats, India) using Spatial Capture–Recapture ‘SCR’ models. We estimate dhole densities to be 12–14.2 individuals/100 sq. km based on a set of SCR models, with ~50 individuals within Wayanad's administrative boundary. Our study presents a methodological improvement in generating population estimates of an important apex predator while also offering ecologically informative insights on a species in dire need of science-based management efforts. Replicating this study across connected reserves and over time can serve as a unified framework for understanding population dynamics, population structures, landscape connectivity and metapopulation-level conservation requirements. We propose that the approach presented here may be adopted as an economically and logistically feasible protocol for conservation monitoring of dholes and other ecologically important species plagued by similar issues of data-deficiency, and insufficient funding and resources.

Revising geographic distributions of eastern Pacific moray eels

Under the influence of climate stressors, species distributions of fishes in the eastern Pacific are shifting, with many species moving poleward. Moray eels (family Muraenidae) are ecologically important predators inhabiting coastal reefs. Due to their cryptic nature and lack of commercial importance, the species distributions of muraenids in the tropical and subtropical eastern Pacific are poorly understood. Here, we document the geographic range size of 33 muraenid species in the eastern Pacific and also report a shift in the established population range of Muraena argus based on recent trapping efforts. We found that 17 species demonstrated shifts in geographic range size, including sampled-range expansions and new occurrences at offshore islands. Eleven species were observed in new biogeographic provinces, primarily in the northward direction to the San Diegan Province. Trapping data and local knowledge gathered from fishing cooperatives suggest that M. argus has established populations at least 300 km further north than previously reported. Both the yearly number of reported observations and geographic extent of sampling have increased over time, but the number of recorded extensions has not. These results highlight the importance of compiling data from diverse sources (including museum records, local ecological knowledge, and the non- English scientific literature) as well as the continued value of biodiversity surveys in the eastern Pacific.

Evaluating the potential of flowering plants for enhancing predatory hoverflies (Syrphidae) for biological control of Diaphorina citri (Liviidae) in California

Diaphorina citri (Hemiptera: Liviidae) is a notorious citrus pest that vectors a bacterium that causes huanglongbing, a lethal citrus disease. Studies evaluating the potential of buckwheat (Fagopyrum esculentum), alyssum (Lobularia maritima), phacelia (Phacelia tanacetifolia), and California poppy (Eschscholzia californica) as insectary plants for conservation biological control of D. citri were conducted in California citrus orchards. Field studies assessed flowering phenology and attractiveness to hoverflies and other natural enemies, hoverfly oviposition on D. citri colonies, and the effect of potted alyssum and predation from hoverflies on the mortality of D. citri nymphs. Laboratory studies quantified lifetime consumption of D. citri nymphs by individual Allograpta obliqua (Diptera: Syrphidae) larvae, the only hoverfly species attacking D. citri in the field. Results indicated that alyssum and buckwheat possessed a short sowing to flowering time (30–33 days when sown in March) and attracted 10–20 times more syrphids than California poppy. No hoverflies were observed feeding from phacelia. California poppy was marginally attractive to hoverflies, and failed to attract ladybugs, parasitoids, or predatory wasps. When alyssum was present in an unsprayed citrus orchard, the number of hoverfly eggs laid on D. citri colonies and abundance of predators was 3.5 times and 2.5 times higher, respectively, when compared to control plots lacking alyssum. Consequently, 10% more D. citri nymphs survived to adulthood in the control plots compared to alyssum plots. In the laboratory, individual A. obliqua larvae consumed, on average, 421 D. citri nymphs before pupation. Results demonstrate that A. obliqua is an important and voracious predator of D. citri nymphs, and that alyssum and buckwheat show potential as insectary plants for conservation biological control of D. citri.

Predicting Damage to Hop Cones by Tetranychus urticae (Acari: Tetranychidae).

Twospotted spider mite (Tetranychus urticae Koch) is a cosmopolitan pest of numerous plants, including hop (Humulus lupulus L.). The most costly damage from the pest on hop results from infestation of cones, which are the harvested product, which can render crops unsalable if cones become discolored. We analyzed 14 yr of historical data from 312 individual experimental plots in western Oregon to identify risk factors associated with visual damage to hop cones from T. urticae. Logistic regression models were fit to estimate the probability of cone damage. The most predictive model was based on T. urticae-days during mid-July to harvest, which correctly predicted occurrence and nonoccurrence of cone damage in 91 and 93% of data sets, respectively, based on Youden's index. A second model based on the ratio of T. urticae to predatory arthropods late in the season correctly predicted cone damage in 92% of data sets and nonoccurrence of damage in 77% of data sets. The model based on T. urticae abundance performed similarly when validated in 23 commercial hop yards, whereas the model based on the predator:prey ratio was relatively conservative and yielded false-positive predictions in 11 of the 23 yards. Antecedents of these risk factors were explored and quantified by structural equation modeling. A simple path diagram was constructed that conceptualizes T. urticae invasion of hop cones as dependent on prior density of the pest on leaves in early spring and summer, which in turn influences the development of predatory arthropods that mediate late-season density of the pest. In summary, the biological insights and models developed here provide guidance to pest managers on the likelihood of visual cone damage from T. urticae that can inform late-season management based on both abundance of the pest and its important predators. This is critically important because a formal economic threshold for T. urticae on hop does not exist and current management efforts may be mistimed to influence the pest when crop damage is most probable. More broadly, this research suggests that current management practices that target T. urticae early in the season may in fact predispose yards to later outbreaks of the pest.

Chaoborus flavicans Meigen (Diptera, Chaoboridae) is a complex of lake and pond dwelling species: a revision.

Chaoborus flavicans (Meigen) is a widespread and much studied lacustrine phantom midge. As larvae, these insects are important aquatic predators. Based on the available type material, morphology of immature stages and adults, their aquatic habitat, and DNA barcodes, C. flavicans is shown to be a composite of at least four species, with three of these named here. Chaoborus flavicans is primarily a lake-dwelling species with a Holarctic range. Chaoborus albipes (Johannsen, 1903 stat. rev.) and C. posio Salmela sp. n. are pond-dwelling Holarctic and north European species, respectively. The position of the larval subordinate mandibular tooth at the vertex of the second and fourth teeth is a synapomorphy of the Chaoborus flavicans species complex. We present an identification key to fourth instar larvae, pupae, and adult males. We also designate the lectotype and paralectotypes of Sayomyia rotundifolia Felt, 1904 (syn. nov. of C. albipes). We hypothesize that a fourth species of the species complex is present in Japan. Our revision indicates that Holarctic shallow ponds contain a hidden diversity of predators (C. albipes and C. posio sp. n.).

Possible causes of a substantial decline in sightings in South Africa of an ecologically important apex predator, the white shark

A decline in sightings of a top predator, the white shark (Carcharadon carcharias), in South Africa was quantified in order to identify possible causes for this decline. White shark sightings data across 8 years (2011–2018), recorded from a cage-diving vessel in Gansbaai are reported. A significant decline in mean total white shark sightings per boat trip (&gt;6 in 2011 to &lt;1 in 2018) and a 69% reduction in the probability of a sighting were found. Correlating with this decline in sightings is a rise in sightings of sevengill sharks (Notorynchus cepedianus) in False Bay and copper sharks (Carcharhinus brachyurus) in Gansbaai, as well as substantial ecosystem changes. The effects of lethal conservation measures such as the use of shark nets in KwaZulu-Natal; the direct and indirect effects of overfishing including a reduction in smoothhound (Mustelus mustelus) and soupfin (Galeorhinus galeus) sharks; and novel predation on white sharks are discussed as possible causative factors for this decline in white shark sightings.&#x0D; Significance:&#x0D; &#x0D; The results of this paper highlight the need to reassess the impact of marine conservation initiatives and fishing practices. Failure to do so could seriously affect ecologically and economically important marine species. This paper reveals a potentially serious decline to the South African white shark population, characterised by a substantial decline in white shark sightings. This decline correlates with the overfishing of prey species, bycatch, the use of lethal gill nets and ecological changes such as the novel presence of orca. Better marine management is required if South Africa wishes to keep a healthy white shark population.&#x0D;