Sheep Skin Odor Improves Trap Captures of Mosquito Vectors of Rift Valley Fever

In recent years, the East African region has seen an increase in arboviral diseases transmitted by blood-feeding arthropods. Effective surveillance to monitor and reduce incidence of these infections requires the use of appropriate vector sampling tools. Here, trapped skin volatiles on fur from sheep, a known preferred host of mosquito vectors of Rift Valley fever virus (RVFV), were used with a standard CDC light trap to improve catches of mosquito vectors. We tested the standard CDC light trap alone (L), and baited with (a) CO₂ (LC), (b) animal volatiles (LF), and (c) CO₂ plus animal volatiles (LCF) in two highly endemic areas for RVF in Kenya (Marigat and Ijara districts) from March–June and September–December 2010. The incidence rate ratios (IRR) that mosquito species chose traps baited with treatments (LCF, LC and LF) instead of the control (L) were estimated. Marigat was dominated by secondary vectors and host-seeking mosquitoes were 3–4 times more likely to enter LC and LCF traps [IRR = 3.1 and IRR = 3.8 respectively] than the L only trap. The LCF trap captured a greater number of mosquitoes than the LC trap (IRR = 1.23) although the difference was not significant. Analogous results were observed at Ijara, where species were dominated by key primary and primary RVFV vectors, with 1.6-, 6.5-, and 8.5-fold increases in trap captures recorded in LF, LC and LCF baited traps respectively, relative to the control. These catches all differed significantly from those trapped in L only. Further, there was a significant increase in trap captures in LCF compared to LC (IRR = 1.63). Mosquito species composition and trap counts differed between the RVF sites. However, within each site, catches differed in abundance only and no species preferences were noted in the different baited-traps. Identifying the attractive components present in these natural odors should lead to development of an effective odor-bait trapping system for population density-monitoring and result in improved RVF surveillance especially during the inter-epidemic period.     

Vertical distribution of haematophagous Diptera in temperate forests of the southeastern U.S.A.

The vertical distribution of blood‐feeding flies in two temperate forests in the southeastern U.S.A. was determined by placing 15 Centers for Disease Control and Prevention miniature light traps (12 CO₂‐baited, three unbaited controls), without lights, at three heights (1.5 m, 5.0 m, 10.0 m). More than 6550 haematophagous flies, representing 49 species in four families, were collected. Eighteen species were taken almost exclusively (90–100%) at 1.5 m or 10.0 m, and the mean number of flies per trap differed significantly with height for another six species. Five species exhibited shifts in vertical distribution between the two forests, indicating that forest structure could influence the height of host searching. Most (52.5%) mammalophilic flies were collected at 1.5 m, whereas most (56.4%) ornithophilic flies were taken at 10.0 m, suggesting that host associations influence vertical distributions. The significant differences in the composition of haematophagous fly populations among forest strata emphasize the importance of trap placement in vector surveillance and of understanding the ecological relationships of blood‐feeding flies.     

植食性昆虫寄主植物嗅觉搜寻述介

植食性昆虫与寄主植物关系的本质是化学。植食性昆虫搜寻寄主的嗅觉媒介是植物气味即化学信息物质。在介绍植物气味构成及其扩散模型基础上,阐述了植物气味在地上植食性昆虫成虫、幼虫和地下植食性昆虫搜寻寄主过程中的嗅觉导向作用,并指出了今后相关研究需要注意的问题。从植物与环境因子的关系来看,植物气味包括构成性气味和诱发性气味两类,这两类气味的概念既相联系而又不同。构成性气味组分及构成因植物分类地位等而不同。诱发性气味组分因植食性昆虫取食、植物病原微生物、机械致伤等因子的胁迫而变化,这种变化性状随植物属和/或种、植株生长发育阶段、胁迫因子性质及其作用方式而不同。无论是哪种植物气味,其释放均具有节律性。气味扩散过程比较复杂,扩散状态可用数学模型表征。对于地上植食性昆虫成虫,植物气味对其寄主搜寻行为具有导向特异性,重点分析了这种特异性形成的两个假说;鳞翅目昆虫幼虫,能够利用植物化学信息物质趋向寄主植物或回避非寄主植物;地下植食性昆虫搜寻寄主,既与寄主植物地下组织释放或分泌的次级代谢物有关,又与一些初级代谢物有关。初级代谢物中的CO₂,起着“搜寻触发器”作用。有助于增强人们对昆虫与植...     

Volatile host fruit odors as attractants for the oriental fruit fly (Diptera: Tephritidae)

We examined the responses of oriental fruit flies, Bactrocera dorsalis Hendel, to the odors of different stages and types of fruit presented on potted trees in a field cage. Females were most attracted to odors of soft, ripe fruit. Odors of common guava were more attractive to females than papaya and starfruit, and equally as attractive as strawberry guava, orange, and mango. In field tests, McPhail traps baited with mango, common guava, and orange captured equal numbers of females. Traps baited with mango were compared with 2 commercially available fruit fly traps. McPhail traps baited with mango captured more females than visual fruit-mimicking sticky traps (Ladd traps) and equal numbers of females as McPhail traps baited with protein odors. Results from this study indicate that host fruit volatiles could be used as lures for capturing oriental fruit flies in orchards.     

Evaluation of ammonia,human sweat,and bovine blood as attractants for the female canyon fly,Fannia conspicua (Diptera: Muscidae), in southern California

Human sweat, liquid ammonia, and bovine blood are known to be attractive to some hematophagous flies. These materials were evaluated with and without carbon dioxide (CO₂) for their ability to increase capture of female “canyon flies” (Fannia conspicua Malloch) using CDC‐type suction traps (without light). Ammonia acted synergistically with CO₂ to increase trap catch 89.9% over CO₂ alone. There was no synergistic effect of human sweat or bovine blood with CO₂. In the absence of CO₂, none of the three materials increased trap catch of female canyon flies relative to non‐baited traps. Implications for canyon fly control and further trap improvement are discussed.     

Generalist nematodes dominate the nemabiome of roe deer in sympatry with sheep at a regional level

The growth of livestock farming and the recent expansion of wild ungulate populations in Europe favor opportunities for direct and/or indirect cross-transmission of pathogens. Comparatively few studies have investigated the epidemiology of gastro-intestinal nematode parasites, an ubiquitous and important community of parasites of ungulates, at the wildlife/livestock interface. In this study, we aimed to assess the influence of livestock proximity on the gastrointestinal nematode community of roe deer in a rural landscape located in southern France. Using ITS-2 rDNA nemabiome metabarcoding on fecal larvae, we analysed the gastrointestinal nematode communities of roe deer and sheep. In addition, we investigated Haemonchus contortus nad4 mtDNA diversity to specifically test parasite circulation among domestic and wild host populations. The dominant gastrointestinal nematode species found in both the roe deer and sheep were generalist species commonly found in small ruminant livestock (e.g. H. contortus), whereas the more specialised wild cervid nematode species (e.g. Ostertagia leptospicularis) were only present at low frequencies. This is in marked contrast with previous studies that found the nemabiomes of wild cervid populations to be dominated by cervid specialist nematode species. In addition, the lack of genetic structure of the nad4 mtDNA of H. contortus populations between host species suggests circulation of gastrointestinal nematodes between roe deer and sheep. The risk of contact with livestock only has a small influence on the nemabiome of roe deer, suggesting the parasite population of roe deer has been displaced by generalist livestock parasites due to many decades of sheep farming, not only for deer grazing close to pastures, but also at a larger regional scale. We also observed some seasonal variation in the nemabiome composition of roe deer. Overall, our results demonstrate significant exchange of gastrointestinal nematodes between domestic and wild ungulates, with generalist species spilling over from domestic ungulates dominating wild cervid parasite communities.     

Carbonic acid as the host signal for the development of parasitic stages of nematodes

Petronijevic T., Rogers W. P. and Sommerville R. I. 1985. Carbonic acid as the host signal for the development of parasitic stages of nematodes. International Journal for Parasitology15: 661–667. This paper gives results on which may be based an identification of the component of the system CO₂ + H₂O ai H₂CO₃ ai H⁺ HCO₃^? which acts as the stimulus from the animal host for some nematodes. Using infective juveniles of Nematospiroides dubius and Haemonchus contortus, the effects on exsheathment of (1) low pCO₂ values, (2) the presence of carbonic anhydrase in the stimulating medium, and (3) the inhibition of carbonic anhydrase within the juveniles have been examined. The results lead to the suggestion that it is the “readily available” undissociated H₂CO₃, or H₂CO₃ + HCO₃^? which is the critical factor in the stimulus for development. The wide range of [H⁺]s over which “readily available” H₂CO₃ is present in physiological environments suggests that this host signal may be important for infection with many species.     

Development of a Novel Trap for the Collection of?Black Flies of the Simulium ochraceum?Complex

Background

Human landing collections are currently the standard method for collecting onchocerciasis vectors in Africa and Latin America. As part of the efforts to develop a trap to replace human landing collections for the monitoring and surveillance of onchocerciasis transmission, comprehensive evaluations of several trap types were conducted to assess their ability to collect Simulium ochraceum sensu lato, one of the principal vectors of Onchocerca volvulus in Latin America.

Methodology/Principal Findings

Diverse trap designs with numerous modifications and bait variations were evaluated for their abilities to collect S. Ochraceum s.l. females. These traps targeted mostly host seeking flies. A novel trap dubbed the “Esperanza window trap” showed particular promise over other designs. When baited with CO₂ and BG-lure (a synthetic blend of human odor components) a pair of Esperanza window traps collected numbers of S. Ochraceum s.l. females similar to those collected by a team of vector collectors.

Conclusions/Significance

The Esperanza window trap, when baited with chemical lures and CO₂ can be used to collect epidemiologically significant numbers of Simulium ochraceum s.l., potentially serving as a replacement for human landing collections for evaluation of the transmission of O. volvulus.     

Interactions of Carbon Dioxide and Food Odours in Drosophila: Olfactory Hedonics and Sensory Neuron Properties

Behavioural responses of animals to volatiles in their environment are generally dependent on context. Most natural odours are mixtures of components that can each induce different behaviours when presented on their own. We have investigated how a complex of two olfactory stimuli is evaluated by Drosophila flies in a free-flying two-trap choice assay and how these stimuli are encoded in olfactory receptor neurons. We first observed that volatiles from apple cider vinegar attracted flies while carbon dioxide (CO₂) was avoided, confirming their inherent positive and negative values. In contradiction with previous results obtained from walking flies in a four-field olfactometer, in the present assay the addition of CO₂ to vinegar increased rather than decreased the attractiveness of vinegar. This effect was female-specific even though males and females responded similarly to CO₂ and vinegar on their own. To test whether the female-specific behavioural response to the mixture correlated with a sexual dimorphism at the peripheral level we recorded from olfactory receptor neurons stimulated with vinegar, CO₂ and their combination. Responses to vinegar were obtained from three neuron classes, two of them housed with the CO₂-responsive neuron in ab1 sensilla. Sensitivity of these neurons to both CO₂ and vinegar per se did not differ between males and females and responses from female neurons did not change when CO₂ and vinegar were presented simultaneously. We also found that CO₂-sensitive neurons are particularly well adapted to respond rapidly to small concentration changes irrespective of background CO₂ levels. The ability to encode temporal properties of stimulations differs considerably between CO₂- and vinegar-sensitive neurons. These properties may have important implications for in-flight navigation when rapid responses to fragmented odour plumes are crucial to locate odour sources. However, the flies’ sex-specific response to the CO₂-vinegar combination and the context-dependent hedonics most likely originate from central rather than peripheral processing.     

Comparative efficacy of three suction traps for collecting phlebotomine sand flies (Diptera: Psychodidae) in open habitats

The efficacy of three suction traps for trapping phlebotomine sand flies (Diptera: Psychodidae) was compared. Traps were baited with Co₂ and used without any light source. CO₂‐baited CDC traps were evaluated either in their standard downdraft orientation or inverted (iCDC traps). Mosquito Magnet‐X (MMX) counterflow geometry traps were tested in the updraft orientation only. Both updraft traps (iCDC and MMX) were deployed with their opening ～10 cm from the ground while the opening of the downdraft (CDC) trap was ～40 cm above ground. Comparisons were conducted in two arid locations where different sand fly species prevail. In the Jordan Valley, 3,367 sand flies were caught, 2,370 of which were females. The predominant species was Phlebotomus (Phlebotomus) papatasi, Scopoli 1786 (>99%). The updraft‐type traps iCDC and MMX caught an average of 118 and 67.1 sand flies per trap night, respectively. The CDC trap caught 32.9 sand flies on average per night, significantly less than the iCDC traps. In the Judean desert, traps were arranged in a 3×3 Latin square design. A total of 565 sand flies were caught, 345 of which were females. The predominant species was P. (Paraphlebotomus) sergenti Parrot 1917 (87%). The updraft traps iCDC and MMX caught an average of 25.6 and 17.9 sand flies per trap per night, respectively. The CDC trap caught 7.8 sand flies on average per night, significantly less than the iCDC traps. The female to male ratio was 1.7 on average for all trap types. In conclusion, updraft traps deployed with their opening close to the ground are clearly more effective for trapping sand flies than downdraft CDC traps in open habitats.     

Invasion of black-tailed deer by nose bot fly larvae (Diptera: Oestridae: Oestrinae)

Invasion of black-tailed deer (Odocoileus hemionus columbianus) by larvae of the nose bot flies (Cephenemyia apicata and C. jellisoni) was investigated by obssrving their expulsion by larviparous females and their subsequent activity on the host. The drying uterine fluid encasing larvae ( = larval packet) delays desiccation, ensures adhesion to hairs, and immediately dissolves upon contact with saliva. Contrary to the widely accepted nasal mode of invasion, larvae placed on muzzles of deer crawl ventrally toward the upper lip, enter the mouth, and then crawl caudally along the hard palate or tongue toward the throat. Hair located between the muzzle and nostril prevents larvae from entering the nostrils. A natural per os mode of invasion, heretofore unrecognized, is proposed. This is initiated by: (1) females depositing larval packets on the muzzle of deer, or (2) deer licking larval packets from contaminated areas around the muzzle. The positive thermotropism of larvae is compatible with such a per os mode of entry into the host.     

The parasitoid fly Exorista japonica uses visual and olfactory cues to locate herbivore‐infested plants

Some parasitoid flies exploit odors derived from plants as olfactory cues for locating the food plants of host insects, but the role of visual cues associated with plants remains largely unknown. The generalist tachinid Exorista japonica Townsend (Diptera: Tachinidae) is attracted to odors derived from maize plants [Zea mays L. (Poaceae)] infested by the larvae of Mythimna separata (Walker) (Lepidoptera: Noctuidae). In this study, we examined the effects of visual parameters on the olfactory attraction of female flies to host‐infested plants. A paper plant model of one of four colors (blue, green, yellow, or red) was placed in front of a host‐infested plant, which was hidden behind a mesh screen in a wind tunnel. The landing rate of females was significantly higher on the green plant model than on the other three models. When an achromatic plant model of one of four gray scales (white, light gray, dark gray, or black) was tested, the response rate of females was significantly higher towards the white model and decreased as the brightness of models decreased. Few female flies responded to the green plant model without odors of the host‐infested plants. When the four color plant models were placed together in a cage filled with odors of host‐infested plants, females remained significantly longer on the green model than on the other three models. These results showed that E. japonica females preferred the color green when odors of the host‐infested plants were present and suggest that E. japonica uses visual as well as olfactory cues to locate the host habitat.     

House Fly (Musca domestica L.) Attraction to Insect Honeydew

House flies are of major concern as vectors of food-borne pathogens to food crops. House flies are common pests on cattle feedlots and dairies, where they develop in and feed on animal waste. By contacting animal waste, house flies can acquire human pathogenic bacteria such as Escherichia coli and Salmonella spp., in addition to other bacteria, viruses, or parasites that may infect humans and animals. The subsequent dispersal of house flies from animal facilities to nearby agricultural fields containing food crops may lead to pre-harvest food contamination with these pathogens. We hypothesized that odors from honeydew, the sugary excreta produced by sucking insects feeding on crops, or molds and fungi growing on honeydew, may attract house flies, thereby increasing the risk of food crop contamination. House fly attraction to honeydew-contaminated plant material was evaluated using a laboratory bioassay. House flies were attracted to the following plant-pest-honeydew combinations: citrus mealybug on squash fruit, pea aphid on faba bean plants, whitefly on navel orange and grapefruit leaves, and combined citrus mealybug and cottony cushion scale on mandarin orange leaves. House flies were not attracted to field-collected samples of lerp psyllids on eucalyptus plants or aphids on crepe myrtle leaves. Fungi associated with field-collected honeydews were isolated and identified for further study as possible emitters of volatiles attractive to house flies. Two fungal species, Aureobasidium pullulans and Cladosporium cladosporioides, were repeatedly isolated from field-collected honeydew samples. Both fungal species were grown in potato dextrose enrichment broth and house fly attraction to volatiles from these fungal cultures was evaluated. House flies were attracted to odors from A. pullulans cultures but not to those of C. cladosporioides. Identification of specific honeydew odors that are attractive to house flies could be valuable for the development of improved house fly baits for management of this pest species.     

Opportunist slave-making ants Myrmoxenus ravouxi discriminate different host species from a non-host species

Slave-making ants exploit the worker force of host colonies permanently and have to make recurrent raids in order to replenish the slave’s stock. Some of these parasite species exploit different host species and few studies so far have been devoted to host species recognition mechanisms. Here, we tried to determine if opportunist slave-making ants using different host species rely on innate or experience-induced preferences to discriminate host from non-host species. We show that Myrmoxenus ravouxi slave-making workers are not only more aggressive toward heterocolonial host and potential host species workers when compared with non-host species workers, but also toward heterocolonial host workers than toward heterocolonial conspecifics. Moreover, M. ravouxi workers display more antennations and contacts toward the heterocolonial host species when compared with the non-host species. We also show that they do not discriminate between homocolonial and heterocolonial conspecifics. Together, our results suggest that this opportunistic slave-making ant species may have a complex social recognition template based on both innate and experience-based mechanisms.     

Additive and synergistic integration of multimodal cues of both hosts and non-hosts during host selection by woodboring insects

Host selection by herbivorous insects is primarily thought to depend on attraction to olfactory cues emitted from the host species. However, the discrimination of these hosts from non-host species may also arise from the adaptive detection and avoidance of non-host cues, including visual characteristics. Many generalist, conifer-colonising beetles, for example, use characteristic volatiles to identify and discriminate against non-host angiosperm trees such as aspens and birches while flying. These trees also differ in bark reflectance characteristics, which could also mediate host/non-host discrimination by interacting with semiochemicals. We tested this hypothesis by evaluating the responses of eight species of polyphagous woodboring beetles to traps which simulated the visual appearance of coniferous hosts (black) and angiosperm non-hosts (white), and which were baited with host or non-host volatiles. As predicted, three species of large woodboring beetle and a woodboring wasp all avoided white, non-host-simulating traps that were baited with attractive kairomones, and preferred black, host-simulating traps. Conversely, three ambrosia beetle species demonstrated weaker visual preferences, possibly because they preferentially colonise fallen hosts that would transmit less accurate visual information. However, the ambrosia beetle Trypodendron lineatum did show a greater preference for host-coloured traps when these released host-associated kairomones in addition to their pheromone, and also avoided white non-host traps, but only when these released non-host volatiles. To our knowledge, this is the first evidence that multiple non-host cues could synergistically mediate the adaptive discrimination of hosts and non-hosts. Our results suggest that successful host location by generalists arises from the complex integration of cues in multiple sensory modes, and that foraging herbivores evaluate both hosts and non-hosts during their search.     

Prospects for Developing Odour Baits To Control Glossina fuscipes spp., the Major Vector of Human African Trypanosomiasis

We are attempting to develop cost-effective control methods for the important vector of sleeping sickness, Glossina fuscipes spp. Responses of the tsetse flies Glossina fuscipes fuscipes (in Kenya) and G. f. quanzensis (in Democratic Republic of Congo) to natural host odours are reported. Arrangements of electric nets were used to assess the effect of cattle-, human- and pig-odour on (1) the numbers of tsetse attracted to the odour source and (2) the proportion of flies that landed on a black target (1×1 m). In addition responses to monitor lizard (Varanus niloticus) were assessed in Kenya. The effects of all four odours on the proportion of tsetse that entered a biconical trap were also determined. Sources of natural host odour were produced by placing live hosts in a tent or metal hut (volumes≈16 m³) from which the air was exhausted at ∼2000 L/min. Odours from cattle, pigs and humans had no significant effect on attraction of G. f. fuscipes but lizard odour doubled the catch (P<0.05). Similarly, mammalian odours had no significant effect on landing or trap entry whereas lizard odour increased these responses significantly: landing responses increased significantly by 22% for males and 10% for females; the increase in trap efficiency was relatively slight (5–10%) and not always significant. For G. f. quanzensis, only pig odour had a consistent effect, doubling the catch of females attracted to the source and increasing the landing response for females by ∼15%. Dispensing CO₂ at doses equivalent to natural hosts suggested that the response of G. f. fuscipes to lizard odour was not due to CO₂. For G. f. quanzensis, pig odour and CO₂ attracted similar numbers of tsetse, but CO₂ had no material effect on the landing response. The results suggest that identifying kairomones present in lizard odour for G. f. fuscipes and pig odour for G. f. quanzensis may improve the performance of targets for controlling these species.     

The basis for host plant specificity inTephritis dilacerata andT. Formosa [Dipt: Tephritidae]

Strains ofTephritis dilacerata Loew andT. formosa Loew from galls onSonchus arvensis L. andS. asper (L.)Hill, respectively, could be raised reliably in the laboratory only on their host plants. Ovipositing females of both tephritids select a narrow, but different, range of bud sizes. The hatching of the eggs of both flies is synchronized with the onset of rapid but elongation in their respective host plants. Because the growth characteristics of these 2Sonchus species are different, buds of equivalent developmental stages are different average sizes, and ovipositional behavior that brings about synchronization onS. arvensis is not adapted toS. asper and vice versa. Both flies occasionally laid into the flower buds of each others host plant as well asS. oleraceus L. In these cases the buds aborted or the larvae failed to complete normal development. However, both flies appear to be preadapted to the non-host plantSonchus species in this group and host records forT. dilacerata andT. formosa suggest the existence of “host races” attacking theseSonchus species, or alternatively, the frequent occurrence of ovipositional “mistakes” involving these plants.     

Effect of CO2 concentration on mosquito collection rate using odor‐baited suction traps

Carbon dioxide (CO₂) has been used for decades to enhance capture of host‐seeking mosquitoes when released in association with traps commonly used by mosquito and vector control agencies. However, there is little published work evaluating the effect of altering CO₂ release rates relative to the number of mosquitoes captured in these traps. This study investigated how varying CO₂ concentration altered the mosquito collection rate at a freshwater wetlands in southern California. Host‐seeking mosquitoes were captured in CDC‐style traps baited with one of six CO₂ release rates ranging from 0–1,495 ml/min from gas cylinders. Species captured were Aedes vexans, Anopheles franciscanus, An. hermsi, Culex erythrothorax, and Cx. tarsalis. A biting midge, Culicoides sonorensis, was also captured. For all species, increasing CO₂ release rates resulted in increasing numbers of individual females captured, with the relative magnitude of this increase associated to some extent with known feeding preferences of these species. We found that variation in CO₂ release rate can significantly alter mosquito capture rates, potentially leading to imprecise estimates of vector activity if the relationship of CO₂ release rate to mosquito capture rate is not considered.     

ACTION DE L'ANHYDRIDE CARBONIQUE ET DE FACTEURS VISUELS SUR LES PERFORMANCES DE PIEGES «MANITOBA» MODIFIES EN MILIEU MONTAGNARD

Résumé Les performances de pièges à Tabanidae de type Manitoba ont été étudiées en milieu montagnard et subalpin. On a testé les influences respectives de la présence ou de l'absence d'une source de CO₂, de la nature de cette source (solide ou gazeuse), de la présence ou de l'absence d'un leurre visuel (sphère noir brillant), de la nature transparente ou opaque de la partie supérieure du piège (hotte conique). Plus de 8.000 Tabanidae et plus de 51.000 Muscidae ont été pris au cours de ces essais totalisant 660 heures-pièges.

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Summary Manitoba traps, traps without decoy or with black canopy, unbaited or baited with dry ice or compressed carbon dioxide, were compared for the numbers of horse flies and muscid flies caught in mountainous mixed wood and pasture land and in subalpine larch forest between 1500 m and 2200 m, in July. More muscid flies were captured in the compressed CO₂ baited traps than in dry ice baited traps. Haematopota pluvialis, Tabanus maculicornis and Tabanus quatuornotatus were more attracted by CO₂ than Tabanus bromius. T. bromius was more attracted by the decoy than other species. The genus Atylotus and T. bromius are more attracted to the black canopy than other species. The visual decoy is more necessary to the efficiency of the trap than the chemical bait. The CO₂ baited Manitoba trap caught the greatest number of horse flies (180 per trap and per hour). The unbaited Manitoba trap was efficient too, but other traps were inefficient. About 8000 horse flies and 51000 muscid flies were caught.