Functional morphology of the retina of Chrysops caecutiens L. and Haematopota pluvialis L. (Diptera : Tabanidae): Region around eye equator
The ommatidia in the midregion of the eyes of females in 2 tabanid species, Chrysops caecutiens L. and Haematopota pluvialis L. (Diptera : Tabanidae) are compared with those in muscoid flies. They conform in their basic fine structure to ommatidia of other dipterans. However, whereas in this part of the retina of higher dipterans the rhabdomeres of all the retinula cells are twisted, in the tabanids only the peripheral rhabdomeres R1–6 twist. The central retinula cells R7 can be assigned to 3 morphological types, depending on the orientation of the microvilli and rhabdomeres: (i) dorsal (or ventral in the lower eye part); (ii) frontal; or (iii) caudal. Cells of these 3 types are distributed within the ommatidial array in an irregular pattern. The microvilli of the retinula cells R8 are all oriented in the same direction, approximately dorsoventral. All the central rhabdomeres in the midregion of the retina are untwisted. This could subserve high polarization sensitivity of the retinula cells R7/8, which may assist in host-finding by these bloodsucking flies.
Available from: Gyorgy Kriska
- "2012a ) —catch water - seeking male and female specimens . These traps utilize the polarization sensi - tivity of tabanid eyes ( Wunderer and Smola 1986 ) and the positive polarotaxis of tabanids ; that is , these flies are attracted to linearly polarized light : horizontally polarized light attracts water - seeking males and females ( Horváth et al . 2008 ; Kriska et al . "
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ABSTRACT: Blood-sucking female tabanid flies cause serious problems for animals and humans. For the control of tabanids, the knowledge about their seasonality and daily activity is of great importance. Earlier, only traditional traps capturing exclusively female tabanids have been used to survey tabanid activity. The data of such temporal trapping do not reflect correctly the activity of male and female tabanid flies. Our major aim was to monitor the trapping numbers of male and female tabanids during a 3-month summer survey in Hungary. We used (i) conventional canopy traps with liquid traps on the ground beneath the canopy and (ii) L-shaped sticky traps with vertical and horizontal components. Our other goal was to compare the efficiencies of the two components of each trap type used. We observed two greater peaks of the trapping number of tabanids. These peaks started with increased catches of female tabanids captured by the canopy traps and the vertical sticky traps and ended with a dominance of male and female tabanids caught by the liquid traps and the horizontal sticky traps. The swarming periods were interrupted by rainy/cool days, when the number of tabanids decreased drastically. Among the 17 species, six dominated and composed 89.4 % of the captured tabanids: Haematopota pluvialis, Tabanus tergestinus, Tabanus bromius, Tabanus maculicornis, Tabanus bovinus and Atylotus loewianus. The number of water-seeking male and female tabanids rose up to 12-13 h and then decreased but had a secondary peak at about 17 h. The stochastic weather change and the communities of different species resulted in large standard deviations of the averaged number of tabanids in the course of a day. The horizontally polarizing (liquid and horizontal sticky) traps captured both male and female specimens and were about three times more efficient than the canopy and vertical sticky traps that caught only females. The results of the horizontal sticky traps corresponded to those of the liquid traps, while the catches of the vertical sticky traps corresponded to those of the canopy traps. The catches of the used trap types reflected well the species and water/host-seeking composition of tabanids.
Available from: Gerard Duvallet
- "Tabanids are mainly diurnal, and optical cues are relevant for mating, host location and oviposition. The ventral eye region has special morphological features that indicate high polarization sensitivity (Wunderer and Smola, 1986). Horizontally polarized light is attractive to both male and female tabanids (Egri et al., 2012b; Horváth et al., 2008). "
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ABSTRACT: Tabanids are nuisance pests for people and livestock because of their painful and irritating bite, persistent biting behavior, and blood ingestion. About 4,400 tabanid species have been described; they are seasonally present in all kinds of landscapes, latitudes, and altitudes. High populations have a significant economic impact on outdoor activities, tourism, and livestock production. Tabanids are also vectors of animal disease agents, including viruses, bacteria and parasites. However, tabanids have received little attention in comparison with other hematophagous Diptera. Here, we highlight the many direct and indirect impacts of tabanids and provide a brief summary of tabanid morphology, biology, and life cycle. Impacts include pathogen transmission, parasite transportation (Dermatobia hominis), biological transmission (Loa loa), and mechanical transmission of viruses, such as equine infectious anemia virus, protozoa, such as Trypanosoma evansi and Besnotia besnoiti, and bacteria, such as Bacillus anthracis and Anaplasma marginale. We discuss parameters of mechanical transmission and its mathematical modeling. Control methods for tabanid populations are also summarized; these include trapping, the use of insecticides, repellents, and livestock protection. Lastly recommendations are provided for the direction of future research.
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ABSTRACT: The morphology of the sensilla sensitive to vertebrate host-associated stimuli is diverse reflecting the numerous independent origins of haematophagy within the insects. Using electron microscopic techniques, the sensilla of mosquitoes and blackflies have been the most thoroughly studied, although numerous works have been conducted on other blood-feeders. Notably lacking are fine structure studies on blood-feeding maggots and ectoparasitic, adult Muscomorpha.In comparing blood-feeders with other insects it becomes apparent that: (1) carbon dioxide plays a significantly greater role in location of food by haematophagous insects than by phytophagous and saprophagous species; (2) only in blood-feeders do the adenosine phosphate nucleotides, a single group of compounds, appear to be the phagostimulants for almost all species; and (3) feeding deterrents are unknown in haematophagous insects.When the sensory complements of the various groups of blood-feeders are compared, three points emerge. First, reduction in numbers of olfactory chemosensilla that mediate odour cues used in long-distance, host-orientation occurs in male nematocerans and in females of completely autogenous species of mosquitoes and black flies. Second, there is a striking correlation between the number of labial chemo- and mechanosensilla and the feeding behaviour of the insect. Third, there is a possible positive correlation between the number of chemosensitive antennal neurones and the distance travelled by the insect to the host.
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