Sugar‐feeding status alters biting midge photoattraction

The biting midge Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae) transmits pathogens to both livestock and wildlife. Biting midge surveillance relies heavily on light traps for collection; however, little is known about the light spectra preferences of C. sonorensis midges. A light assay arena was constructed and light‐emitting diodes (LEDs) of various light spectra were used as light sources to evaluate midge photoattraction. A comparison of responses to light spectra indicated the highest proportions of C. sonorensis were attracted to ultraviolet (UV) light and that midges differentiated 10‐nm differences in wavelength. Stronger intensities of UV light resulted in greater attraction. Midges exhibited both sugar‐seeking and escape behaviours under different conditions of sugar supplementation before and during the experiment. These behaviours occurred with lights of 355 nm and 365 nm in wavelength. Based on the results of this study, the attraction of C. sonorensis to light traps can be improved through the use of bright LEDs at 355 nm or 365 nm.     

Influence of light and kairomone baiting systems on trap collections of biting midges in southern Sweden

Effective surveillance is essential for protecting livestock from Culicoides biting midges and the viruses they transmit. The objective of this study was to determine how the baiting system used in traps (UV, incandescent light, incandescent light with CO₂, and incandescent light with CO₂ and 1‐octen‐3‐ol) influences estimates of midge population abundance, parity, and diel activity. This was achieved through a standardized trapping protocol conducted in three habitats in Sweden. UV light traps caught the most Culicoides species and more C. obsoletus complex females than incandescent light traps. Traps baited with CO₂ plus 1‐octen‐3‐ol caught more female C. impunctatus than incandescent light traps. No consistent effect of bait type was found on C. obsoletus parity rate, as estimated from the proportion of midges with presence or absence of pigmentation. Midge activity, as reflected by trap catches, peaked between ‐3 h and +3 h relative to sunset, with UV traps catching significantly more female C. obsoletus complex and C. impunctatus at and after sunset than before sunset. We conclude that baiting system can influence biting midge collections, even using identical traps. Effective surveillance may require more than one bait type and kairomones to attract species that do not feed exclusively on cattle.     

Principal climatic and edaphic determinants of Culicoides biting midge abundance during the 2007–2008 bluetongue epidemic in the Netherlands,based on OVI light trap data

Palaearctic Culicoides midges (Diptera: Ceratopogonidae) represent a vital link in the northward advance of certain arboviral pathogens of livestock such as that caused by bluetongue virus. The effects of relevant ecological factors on weekly Culicoides vector abundances during the bluetongue virus serotype 8 epidemics in the Netherlands in 2007 and 2008 were quantified within a hurdle modelling framework. The relative role of meteorological parameters showed a broadly consistent association across species, with larger catches linked to temperature‐related variables and lower wind speed. Moreover, vector abundance was found to be influenced by edaphic factors, likely related to species‐specific breeding habitat preferences that differed markedly amongst some species. This is the first study on Culicoides vector species in the Netherlands identified during an entomological surveillance programme, in which an attempt is made to pinpoint the factors that influence midge abundance levels. In addition to providing key inputs into risk‐mitigating tools for midge‐borne pathogens and disease transmission models, the adoption of methods that explicitly address certain features of abundance datasets (frequent zero‐count observations and over‐dispersion) helped enhance the robustness of the ecological analysis.     

Seasonal variation in abundance and diversity of eavesdropping frog‐biting midges (Diptera,Corethrellidae) in a neotropical rainforest

1. In the tropics, precipitation patterns result in seasonal fluctuations in the abundance and distribution of plant and animal species. Tropical predators and parasites are therefore faced with seasonal changes in prey and host availability. 2. This study investigates the seasonal interaction among a specialised ectoparasite, eavesdropping frog‐biting midges (Corethrella spp.), and their anuran hosts, examining how the abundance and diversity of the frog‐biting midge community fluctuate between the rainy (host abundant) and dry (host sparse) seasons. 3. Midges were captured in both the rainy and dry seasons using acoustic playbacks of calls from a common frog species that breeds during the rainy season, the túngara frog (Engystomops, Physalaemus, pustulosus). During the dry season túngara frog choruses are absent. To explore seasonal shifts in host preference or changes in the midge community due to host specificity, midges were also captured using playbacks of calls from a frog that breeds during the dry season, the pug‐nosed tree frog (Smilisca sila). 4. While the overall abundance of midges decreased in the dry season, only slight differences in the relative abundance between midge species were found. These results suggest that midge populations can shift between hosts as they become available across seasons, allowing adult populations of frog‐biting midges to persist year‐round. To overcome the challenge of detecting and localising different host species, it is proposed that frog‐biting midges have evolved a generalised acoustic template, allowing them to respond to a broad range of available hosts, regardless of seasonal host composition.     

Insecticidal sugar baits for adult biting midges

The mixing of an insecticide with sugar solution creates an oral toxin or insecticidal sugar bait (ISB) useful for reducing adult insect populations. The ability of ISBs to kill the biting midge Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae), a vector of bluetongue virus, epizootic hemorrhagic disease and vesicular stomatitis viruses, was tested. The commercial insecticide formulations (percentage active ingredient) tested included bifenthrin, cyfluthrin, deltamethrin, permethrin, dinotefuran, imidacloprid, thiamethoxam and spinosad. Mortality rates were determined for various concentrations of commercial formulations (0.01, 0.05, 0.1, 1, 2 and 3%) and observed at 1, 4, 10 and 24 h post‐exposure to the ISB. In the first set of assays, laboratory‐reared midges were fed sugar ad libitum and then exposed to insecticide‐treated sugar solutions to measure mortality. The second assay assessed competitive feeding: midges were provided with a control sugar solution (10% sucrose) in one vial, and a sugar and insecticide solution in another. Pyrethroid treatments resulted in the greatest mortality in the first hour at the lowest concentrations and spinosad consumption resulted in the least mortality. Biting midges were not deterred from feeding on the 1% ISB solutions despite the presence of an insecticide‐free alternative source of sugar.     

The influence of environmental management and animal shelters in vector control of Culicoides (Diptera,Ceratopogonidae) in northeastern Brazil

We investigated whether biting midges in peridomestic environments are affected by environmental management practices and the presence of domestic animals. We used CDC light traps to collect midges in 112 residences across 24 locations along tourism routes of Maranhão, Brazil. The collection areas were characterized as follows: i) peridomestic area with domestic animals and without management (dirty); ii) peridomestic with domestic animals and management (clean); iii) peridomestic without animals and with management (clean); iv) peridomestic without animals and without management (dirty). The first two treatments had higher biting midge species richness and abundance, respectively. Generalized linear models indicated a positive correlation between the presence of domestic animals and midge abundance, with an approximate four‐fold increase in Culicoides (Diptera: Ceratopogonidae) abundance in peridomestic areas with animals. The same model showed that domestic animals have no influence on richness. Environmental management does not appear to influence species richness or abundance of biting midges.     

Positive indirect effect of aquatic insects on terrestrial prey is not offset by increased predator density

1. Changes in one prey species' density can indirectly affect the abundance of another prey species if a shared predator eats both species. Sometimes, indirect effects occur when prey straddle habitats, including when riparian predator populations grow in response to emergent aquatic insects and increase predation on terrestrial prey. However, predators may largely switch to aquatic insects or become satiated, reducing predation on terrestrial prey. 2. To determine the net indirect effect of aquatic insects on terrestrial arthropods via generalist spider predators, a field experiment was conducted mimicking midge influx and a wolf spider numerical response inside enclosures near an Icelandic lake. Lab mesocosms were also used to assess per capita rates of spider predation u nder differing levels of midge abundance. 3. Midges always decreased sentinel prey predation, but this effect increased with predator density. When midges were absent, predation increased 30% at a high spider density, but predation was equal between spider treatments when midges were present. In situ arthropods showed no effect of midge or spider treatments, although non‐significant abundance patterns were observed congruent with sentinel prey results. 4. In lab mesocosms, prey survivorship increased ≥50% where midges were present and rapidly saturated; the addition of 5, 20, 50, and 100 midges equivalently reduced spider predation, supporting predator distraction rather than satiation as the root cause. 5. The present results demonstrate a strong positive indirect effect of midges and broadly support the concept that predator responses to alternative prey are a major influence on the magnitude and direction of predator‐mediated indirect effects.     

Trap placement and attractant choice affect capture and create sex and parity biases in collections of the biting midge,Culicoides sonorensis

Culicoides sonorensis Wirth & Jones (Diptera: Ceratopogonidae) is the primary North American vector of bluetongue virus (BTV), which can cause high morbidity and mortality in ruminant livestock or wildlife. Worldwide, most Culicoides surveillance relies on light (usually UV) traps typically placed near animals or larval development sites. However, the trapping method can cause sex, species and parity biases in collections. We collected C. sonorensis from three dairies in California using suction traps baited with CO₂, UV light or CO₂ + UV placed near animals, wastewater ponds, or in fields. Higher numbers of parous females were collected using CO₂ + UV traps, although this difference was only significant on one dairy. UV traps were poor at collecting nulliparous females, but the addition of UV to a trap increased the abundance of males in a collection. Traps set in open fields collected significantly higher numbers of males and females than in either of the other two locations. In some cases, there was a significant interaction between the trap type and site. We discuss the limitations of traditional trapping methodologies for C. sonorensis and make suggestions for vector surveillance.     

The Biting Midge Culicoides sonorensis (Diptera: Ceratopogonidae) Is Capable of Developing Late Stage Infections of Leishmania enriettii

BackgroundDespite their importance in animal and human health, the epidemiology of species of the Leishmania enriettii complex remains poorly understood, including the identity of their biological vectors. Biting midges of the genus Forcipomyia (Lasiohelea) have been implicated in the transmission of a member of the L. enriettii complex in Australia, but the far larger and more widespread genus Culicoides has not been investigated for the potential to include vectors to date.Conclusions/SignificanceWe demonstrate that L. enriettii can develop late stage infections in the biting midge Culicoides sonorensis. This midge was found to be susceptible to L. enriettii to a similar degree as Lutzomyia longipalpis, the vector of Leishmania infantum in South America. Our results support the hypothesis that some biting midges could be natural vectors of the L. enriettii complex because of their vector competence, although not Culicoides sonorensis itself, which is not sympatric, and midges should be assessed in the field while searching for vectors of related Leishmania species including L. martiniquensis and "L. siamensis".     

Comparison of a mouth aspirator and a mechanical vacuum aspirator for the collection of Culicoides midges (Diptera: Ceratopogonidae) in equids

In a controlled field trial, a mechanical vacuum and a mouth aspirator were compared with respect to Culicoides midge catching results. The two collection methods were equally applied to two Haflinger horses. Once every hour between 2 hr before sunset and sunset, midges were aspirated for 3 min directly off from the coat of each horse at the same time. In total, 16 replicate measurement days were made. To get insight into the number of (blood‐fed) midges collected on different body parts, four replicate measurement days were done in which the hourly 3‐min samples for each collecting method were separately collected and counted per body part. Mean number of Culicoides midges collected on the legs and on the belly of the horse was two times and significantly higher by the mechanical vacuum aspirator compared to the mouth aspirator. Although the mean number of Culicoides midges from the other part of the host sampled (head/neck/manes/back/flanks) was comparable between the two methods, the mean number of blood‐fed Culicoides midges was four times and significantly higher collected by the mouth aspirator compared to the mechanical vacuum aspirator. In conclusion, it can be recommended to use a mechanical vacuum aspirator instead of a mouth aspirator for the legs and belly area, where a systematic, stroke‐by‐stroke‐vacuum procedure is recommended. For the rest of the body, it is strongly recommended to use a targeted procedure by visual guidance of the presence of midges. For now, based on this experiment, we can only recommend using the mouth aspirator for this targeted approach. However, it might be worth assessing the use of the mechanical vacuum aspirator in a targeted way for future studies.     

Limited attractant range of the black‐light suction trap for the capture of Culicoides biting midges (Diptera: Ceratopogonidae)

The suction light trap (LT) is a standard tool used to capture Culicoides biting midges, when estimating abundances, and mapping species ranges. The exact range of attraction of the LT is in dispute, however, with several studies indicating the range to vary widely, between 4 and 50 m. In this study, the attractant range of a LT, set at various distances (0, 1, 2, 3, 5 and 8 m) from a cow tethered at pasture, is assessed in two trials conducted on a dairy farm in the Netherlands in 2013 and 2014. In the first trial, sweep‐netting and light‐trapping was performed concurrently. Although a Spearman Rank correlation of 0.89 (P = 0.03) showed the two sets of abundance results to be highly correlated, species prevalence differed significantly according to the method used: the Culicoides obsoletus complex dominated the LT observations, whereas Culicoides chiopterus and Culicoides dewulfi were more abundant in those obtained by sweep‐net, due to the former taxon being largely nocturnal, the latter diurnal. There is a distinct negative logarithmic relationship between Culicoides abundance and distance from the vertebrate host, with midge abundance, in the LT, increasing significantly only when it is placed very close to the bait animal, at a distance of 0–1 m. The sharp decay function in the number of Culicoides caught with increasing distance from the LT, limits the comparison of LT surveillance data obtained under various settings, even from within a climatically homogeneous geographical region such as north‐western Europe.     

The sound of a blood meal: Acoustic ecology of frog‐biting midges (Corethrella) in lowland Pacific Costa Rica

Animal communication systems are often exploited by eavesdropping antagonists, especially predators and ectoparasites. Female frog‐biting midges (Diptera: Corethrellidae) are known to use male anuran advertisement calls to locate their blood hosts, frogs. Here, we use acoustic midge traps broadcasting synthetic and recorded calls to identify those frog call parameters that affect midge attraction. At our study site in Pacific lowland Costa Rica, we found that overall midge attraction was influenced by both spectral and temporal acoustic parameters. Low dominant frequencies (below 1 kHz) and short pulse durations (between 125 and 500 ms) attracted the highest numbers of midges in tests with synthetic sinusoidal pure tones. These preferences partially explained the relative attractiveness of the advertisement calls of ten local frog species. The advertisement calls of the common and widespread Giant Bullfrog, Leptodactylus savagei (Anura: Leptodactylidae), attracted by far the largest number of midges, suggesting that this frog species might be a key resource for frog‐biting midges in Costa Rica. Although we found that calls of different frog species attracted different midge species/morphospecies in statistically different proportions, acoustic niche differentiation among midge species appeared to be moderate, suggesting either a limited degree of host specialization or the use of additional short‐range, that is, chemical, host recognition cues.     

Life history strategy and taxonomic position of gall midges (Diptera: Cecidomyiidae) inducing leaf galls on Styrax japonicus (Styracaceae)

Four gall midge species (Diptera: Cecidomyiidae) that induce leaf galls on Styrax japonicus (Styracaceae) were identified to generic level based on larval morphology. Three of these gall midges, which induce whitish hemiglobular galls, flattened subglobular galls, and purple globular galls, respectively, were identified as three genetically distinct species of Contarinia, and the remaining species, which induces globular galls with dense whitish hairs, was identified as a species of Dasineura. Field surveys in Fukuoka, Japan, revealed that adults of these gall midges emerged and oviposited in late March to mid‐April at Mount Tachibana (approximately 200 m a.s.l.) and in late April to early May at Mount Sefuri (about 1050 m a.s.l.), coinciding with the leaf‐opening season of S. japonicus. Larvae of these gall midges mostly developed into third instars by June and then left their galls and dropped to the ground. These species therefore have a life history strategy that differs from that of another S. japonicus‐associated gall midge, Oxycephalomyia styraci, which overwinters as the first instar in ovate swellings, matures rapidly in spring, and emerges directly from the galls.     

Identification, expression and characterisation of a major salivary allergen (Cul s 1) of the biting midge Culicoides sonorensis relevant for summer eczema in horses

Salivary proteins of Culicoides biting midges are thought to play a key role in summer eczema (SE), a seasonal recurrent allergic dermatitis in horses. The present study describes the identification, expression and clinical relevance of a candidate allergen of the North American midge Culicoides sonorensis. Immunoblot analysis of midge saliva revealed a 66 kDa protein (Cul s 1) that was bound by IgE from several SE-affected (SE+) horses. Further characterisation by fragmentation, mass spectrometry and bioinformatics identified Cul s 1 as maltase, an enzyme involved in sugar meal digestion. A cDNA encoding Cul s 1 was isolated and expressed as a polyhistidine-tagged fusion protein in a baculovirus/insect cell expression system. The clinical relevance of the affinity-purified recombinant Cul s 1 (rCul s 1) was investigated by immunoblotting, histamine release testing (HRT) and intradermal testing (IDT) in eight SE+ and eight control horses. Seven SE+ horses had rCul s 1-specific IgE, whereas only one control animal had IgE directed against this allergen. Furthermore, the HRT showed rCul s 1 induced basophil degranulation in samples from seven of eight SE+ horses but in none of the control animals. rCul s 1 also induced immediate (7/8), late-phase (8/8) and delayed (1/8) skin reactivity in IDT on all SE+ horses that had a positive test with the whole body extract (WBE) of C. sonorensis. None of the control horses showed immediate or delayed skin reactivity with rCul s 1, and only one control horse had a positive late-phase response, while several non-specific late-phase reactions were observed with the insect WBE. Thus, we believe rCul s 1 is the first specific salivary allergen of C. sonorensis to be described that promises to advance both in vitro and in vivo diagnosis and may contribute to the development of immunotherapy for SE in horses.     

Evolutionary radiation of Asteromyia carbonifera (Diptera: Cecidomyiidae) gall morphotypes on the goldenrod Solidago altissima (Asteraceae)

Population divergence of phytophagous insects is often coupled to host‐plant shifts and is frequently attributed to the divergent selective environments associated with alternative host‐plants. In some cases, however, divergence is associated with the use of alternative host‐plant organs of a single host species. The basis of within‐host radiations such as these remains poorly understood. In the present stusy, we analysed the radiation of Asteromyia gall midges occurring both within one host plant species and within a single organ on that host. In this system, four morphologically distinct Asteromyia gall forms (morphs) coexist on the leaves of goldenrod Solidago altissima. Our analyses of amplified fragment length polymorphism and DNA sequence data confirm the genetic differentiation among midges from three gall morphs and reveal evidence of a genetically distinct fourth gall morph. The absence of clear gall morph related clades in the mitochondrial DNA derived phylogenies is indicative of incomplete lineage sorting or recent gene flow, suggesting that population divergence among gall forms is recent. We assess the likely history of this radiation and use the results of phylogenetic analyses along with ecological data on phenology and parasitism rates to evaluate potential hypotheses for the mode of differentiation. These preliminary analyses suggest that diversification of the Asteromyia gall morphs is likely shaped by interactions between the midge, a symbiotic fungus, and parasitoid enemies. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 840–858.     

Olfactory response by the aphidophagous gall midge, Aphidoletes aphidimyza to honeydew from green peach aphid, Myzus persicae

Female adults of the aphidopagous gall midge, Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae), showed an olfactory response to honeydew excreted by the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) under laboratory conditions. The response was only elicited by treatments with honeydew, whereas aphids, aphids with pepper plants or leaves, and pepper plants or leaves were not attractive to the midges. Dose‐dependent responses were observed from whole honeydew, honeydew volatiles extracted in pentane, and honeydew volatiles captured on Porapak Q®. When honeydew was eluted with three sequential pentane washes, a positive response was only observed from the midges for the first wash. Female midges laid more eggs on pepper plants infested with higher densities of M. persicae. The olfactory response of midges to honeydew is discussed with respect to prey location.     

Does weather affect biting fly abundance in avian nests?

Environmental factors may strongly affect avian‐biting fly interactions in different ways because insects are heterothermic organisms that depend greatly on environmental variables to activate their metabolism and behaviour. We studied the effects of weather on both blackfly (Simuliidae) and biting midge Culicoides (Ceratopogonidae) abundance in nests of three passerine species: blue tits Cyanistes caeruleus, great tits Parus major and pied flycatchers Ficedula hypoleuca, breeding in the same area. We controlled for different host‐related factors (hatching date, brood size and host species). Blackfly abundance was negatively related to minimum temperature. In addition, blackfly and biting midge abundances were negatively affected by wind speed measured at 07.00 h, but blackfly abundance was positively associated to wind speed at 18.00 h. We found higher blackfly and biting midge abundances in nests with larger broods breeding later in the season, and significantly higher biting midge abundance in pied flycatcher nests as compared to tit nests. These results represent, to our knowledge, the first report of both environmental and host‐related effects on haematophagous fly abundance in the nests of wild hole‐nesting birds.     

The dying of the light: crepuscular activity in Culicoides and impact on light trap efficacy at temperate latitudes

The light trap is the tool of choice for conducting large‐scale Culicoides (Diptera: Ceratopogonidae) vector surveillance programmes. Its efficacy is in doubt, however. To assess this, hourly changes in Culicoides activity over the 24‐h diel were determined comparatively by way of light trapping and aerial sweeping, and correlated against light intensity. In the Netherlands, sweeping around cattle at pasture revealed that, in early summer, Culicoides are active throughout the diel, and that their abundance peaks during the crepuscular period and falls to a low during the brightest hours of the day. By contrast, the light trap was able to accumulate Culicoides only at night (i.e. after illuminance levels had dropped to 0 lux and midge activity had begun to decline). Although Culicoides chiopterus and species of the Culicoides obsoletus complex were similarly abundant around livestock, they differed critically in their hours of peak activity, being largely diurnal and nocturnal, respectively. This polarity helps to explain why, routinely, the C. obsoletus complex dominates light trap collections and C. chiopterus does not. Inability to accumulate Culicoides at light intensity levels above 0 lux means that, at ever‐higher latitudes, particularly beyond 45° N, the progressive northward lengthening of the twilight period will have an increasingly adverse impact upon the efficacy of the light trap as a vector surveillance tool.