Why do biting horseflies prefer warmer hosts? tabanids can escape easier from warmer targets

Blood-sucking horseflies (tabanids) prefer warmer (sunlit, darker) host animals and generally attack them in sunshine, the reason for which was unknown until now. Recently, it was hypothesized that blood-seeking female tabanids prefer elevated temperatures, because their wing muscles are quicker and their nervous system functions better at a warmer body temperature brought about by warmer microclimate, and thus they can more successfully avoid the host's parasite-repelling reactions by prompt takeoffs. To test this hypothesis, we studied in field experiments the success rate of escape reactions of tabanids that landed on black targets as a function of the target temperature, and measured the surface temperature of differently coloured horses with thermography. We found that the escape success of tabanids decreased with decreasing target temperature, that is escape success is driven by temperature. Our results explain the behaviour of biting horseflies that they prefer warmer hosts against colder ones. Since in sunshine the darker the host the warmer its body surface, our results also explain why horseflies prefer sunlit dark (brown, black) hosts against bright (beige, white) ones, and why these parasites attack their hosts usually in sunshine, rather than under shaded conditions

Method to improve the survival of night-swarming mayflies near bridges in areas of distracting light pollution

Numerous negative ecological effects of urban lighting have been identified during the last decades. In spite of the development of lighting technologies, the detrimental effect of this form of light pollution has not declined. Several insect species are affected including the night-swarming mayflyEphoron virgo: when encountering bridges during their mass swarming, these mayflies often fall victim to artificial lighting. We show a simple method for the conservation of these mayflies exploiting their positive phototaxis. With downstream-facing light-emitting diode beacon lights above two tributaries of the river Danube, we managed to guide egg-laying females to the water and prevent them from perishing outside the river near urban lights. By means of measuring the mayfly outflow from the river as a function of time and the on/off state of the beacons, we showed that the number of mayflies exiting the river's area was practically zero when our beacons were operating. Tributaries could be the sources of mayfly recolonization in case of water quality degradation of large rivers. The protection of mayfly populations in small rivers and safeguarding their aggregation and oviposition sites is therefore important.</jats:p

THE HABITAT USE AND SELECTIVITY BY TOPMOUTH GUDGEON (PSEUDORASBORA PARVA)

The topmouth gudgeon is an invasive species of the European fish fauna that causes problems not only as a competitor of native fishes in natural waters but also generates damages in pond fish farming. The behaviour of topmouth gudgeon has already been studied from a number of aspects, however, complex investigations on the habitat use of the species in invaded regions were not carried out yet. Here the habitat use of the fish in a close-tonature pond system was examined with special, non-selective minnow traps and observations were subsequently complemented by aquarium experiments. Our findings revealed that in a pond inhabited by predator fish, topmouth gudgeon preferred the pelagial region, while in a pond free of predator fish, they preferred the littoral zone. The examined abiotic parameters had no effect on the habitat use of the fish. In a simplified artificial environment experiments have yielded the same results. The findings showed that topmouth gudgeon is rather flexible in adapting to the environmental conditions, the available nutrition base, but from the aspect of habitat use the most significant factor is probably the presence of predatory fish. The results can establish an effective suppression method of topmouth gudgeon populations with predator fishes

Természetvédelem és kutatás hazánk egyik legnagyobb gyurgyalag (Merops apiaster Linnaeus, 1758) költőtelepén

Az albertirsai Golyófogó-völgyben található gyurgyalag kolónia több száz méteres löszfalon létesült. Az állomány nagyságát évtizedek óta nyomon követik a helyi természetvédők, az utóbbi években a Jászkun Természetvédelmi Egyesület koordinálásával végzik az állományfelmérést a fal teljes területén. Az egyesület a partfal és a hozzátartozó öthektáros löszgyep megvásárlása után környezetrekonstrukciós munkát kezdett 2003-tól, majd 2009-ben a löszfal rekonstrukcióját is elvégezték. A korábban szemétlerakóként üzemelő bányaudvarban a löszfal felújítását a gyurgyalagok számára kedvező lejtésszög kialakítása és a rajta megtelepedett növényzet eltávolítása révén érték el. Az élőhely-rekonstrukció hatására a 2000-es évek elején 30–50 gyurgyalag párra csökkent helyi állomány növekedésnek indult; 2010-től rendszeresen 200 feletti pár fészkelt itt. A gyurgyalag állományváltozása mellett a fiókák számára hordott rovarokat is felmértük. A mezőgazdasági művelésbe vont területekkel és rétekkel körülvett albertirsai telepnél a hártyásszárnyúak alkották a táplálék felét, emellett a szitakötők, egyenesszárnyúak és kétszárnyúak hasonló, 10% körüli arányban szerepeltek a táplálékban. A terület botanikai érdekességeit, a gyűrűzött és észlelt madárfajok listáját is közöljük

Horsefly reactions to black surfaces: attractiveness to male and female tabanids versus surface tilt angle and temperature

Tabanid flies (Diptera: Tabanidae) are attracted to shiny black targets, prefer warmer hosts against colder ones and generally attack them in sunshine. Horizontally polarised light reflected from surfaces means water for water-seeking male and female tabanids. A shiny black target above the ground, reflecting light with high degrees and various directions of linear polarisation is recognised as a host animal by female tabanids seeking for blood. Since the body of host animals has differently oriented surface parts, the following question arises: How does the attractiveness of a tilted shiny black surface to male and female tabanids depend on the tilt angle δ? Another question relates to the reaction of horseflies to horizontal black test surfaces with respect to their surface temperature. Solar panels, for example, can induce horizontally polarised light and can reach temperatures above 55 °C. How long times would horseflies stay on such hot solar panels? The answer of these questions is important not only in tabanid control, but also in the reduction of polarised light pollution caused by solar panels. To study these questions,we performed field experiments inHungary in the summer of 2019 with horseflies and black sticky and dry test surfaces. We found that the total number of trapped (male and female) tabanids is highest if the surface is horizontal (δ = 0°), and it is minimal at δ = 75°. The number of trapped males decreases monotonously to zero with increasing δ, while the female catch has a primary maximum and minimum at δ=0° and δ = 75°, respectively, and a further secondary peak at δ = 90°. Both sexes are strongly attracted to nearly horizontal (0° ≤ δ ≤ 15°) surfaces, and the vertical surface is also very attractive but only for females. The numbers of touchdowns and landings of tabanids are practically independent of the surface temperature T. The time period of tabanids spent on the shiny black horizontal surface decreases with increasing Tso that above 58 °C tabanids spent no longer than 1 s on the surface. The horizontally polarised light reflected fromsolar panels attracts aquatic insects. This attraction is adverse, if the lured insects lay their eggs onto the black surface and/or cannot escape from the polarised signal and perish due to dehydration. Using polarotactic horseflies as indicator insects in our field experiment, we determined the magnitude of polarised light pollution (being proportional to the visual attractiveness to tabanids) of smooth black oblique surfaces as functions of δ and T