Diurnal Flies Research Articles

Seasonal shift in the diet of the notched-eared bat (Myotis emarginatus) in the Basque Country: from flies to spiders

Myotis emarginatus seems fond of spiders and flies, a unique feeding style among European bats. The importance of each prey type varies among studies, so this paper aims to expand on the knowledge to unveil the trophic niche of M. emarginatus by studying its diet changes throughout the maternity season. We sampled five maternity colonies in the Basque Country every 2 weeks for the whole duration of the maternity season and studied their diet using DNA metabarcoding methods. We observed significant changes in diet diversity and composition. At the beginning of the season, M. emarginatus consumed a variety of prey orders, Diptera being the most abundant; but as the season progressed, the relative consumption of Araneae increased. By August, 80% of the weighted percentage of occurrences (wPOO) corresponded to the orb-web-building spider Araneus diadematus. Orb-web-building spiders need habitats of high vertical complexity to grow in abundance. Therefore, conserving them is essential to preserve attractive hunting grounds for colonies of M. emarginatus. Besides, diurnal flies, mainly Stomoxys calcitrans, were also considerably consumed in the colonies studied, which can become detrimental to the well-being of cattle, and can act as a vector of many diseases.

Speed of phototransduction in the microvillus regulates the accuracy and bandwidth of the rhabdomeric photoreceptor.

Phototransduction reactions in the rhabdomeric photoreceptor are profoundly stochastic due to the small number of participating molecules and small reaction space. The resulting quantum bumps (QBs) vary in their timing (latency), amplitudes and durations, and these variabilities within each cell are not correlated. Using modeling and electrophysiological recordings, we investigated how the QB properties depend on the cascade speed and how they influence signal transfer. Parametric analysis in the model supported by experimental data revealed that faster cascades elicit larger and narrower QBs with faster onsets and smaller variabilities than slower cascades. Latency dispersion was stronger affected by modification of upstream than downstream activation parameters. The variability caused by downstream modifications closely matched the experimental variability. Frequency response modeling showed that corner frequency is a reciprocal function of the characteristic duration of the multiphoton response, which, in turn, is a non-linear function of QB duration and latency dispersion. All QB variabilities contributed noise but only latency dispersion slowed and spread multiphoton responses, lowering the corner frequency. Using the discovered QB correlations, we evaluated transduction noise for dissimilar species and two extreme adaptation states, and compared it to photon noise. The noise emitted by the cascade was non-additive and depended non-linearly on the interaction between the QB duration and the three QB variabilities. Increased QB duration strongly suppressed both noise and corner frequency. This trade-off might be acceptable for nocturnal but not diurnal species because corner frequency is the principal determinant of information capacity. To offset the increase in noise accompanying the QB narrowing during light adaptation and the response-expanding effect of latency dispersion, the cascade accelerates. This explains the widespread evolutionary tendency of diurnal fliers to have fast phototransduction, especially after light adaptation, which thus appears to be a common adaptation to contain stochasticity, improve SNR and expand the bandwidth.

Vision and genesis of survival strategies in tsetse flies: A laboratory study

Organisms respond to environmental stimuli in ways that optimize survival and reproduction. Tsetse fly life-history is characterized by high investment in progeny by the pregnant female and low birth rate. This places constraints on tsetse populations across the sub-Saharan biotopes they colonize where extreme climatic conditions militate against survival. Controlling metabolic rate is crucial in biotopes where daily swings in temperature can exceed 20 °C. Tsetse acquire their nutrient requirements from the blood meal. These diurnal flies are otherwise confined for most of their lives to perching sites in the shade. At these locations they are simultaneously threatened by vertebrate and invertebrate predators. Here we describe behaviours of the East African tsetse Glossina pallidipes Austen (Diptera: Glossinidae) that permit it to reduce risk daily. Newly-emerged flies remain immobile at emergence in the photophase but scotophase-emerging flies walk away within seconds to climb (negative geotaxis) vertical substrates to find a perch off the ground. Flies of all ages show the ability to fly in almost total darkness (1.10−5 lux) in the scotophase to perch on the upper side of horizontally suspended 1 cm diameter bars, simulating branches of vegetation, but perch under the same bars during the photophase. This underlines the predilection of tsetse for objects with a linear aspect that provide a vantage point and shade. Mature G. pallidipes can discriminate between horizontally suspended bars of different diameter and shape. Flicker fusion frequency values established by optomotor and retinogram recordings reveal a higher visual acuity in mature compared to newly-emerged tsetse.

Pollination Ecology of Lowiaceae (Zingiberales): Nocturnal Carrion-Beetle Pollination of Orchidantha virosa

Premise of research. Previous investigations showed the occurrence of diurnal dung-beetle pollination in Orchidantha (Lowiaceae). Though many dung, carrion, and scavenger beetles are exclusively nocturnal, comprehensive night observations were never performed for this genus. In addition, some small mammals were occasionally observed feeding on flowers of Orchidantha during the night. Thus, the present study of pollination biology with observations throughout night fills a significant gap in our knowledge of the ecology of these plants.Methodology. Pollination of O. virosa was studied using day and night visual observations as well as video and photo monitoring. Pollen grains, flowers, and captured pollinators were investigated using LM and SEM.Pivotal results. The flowers of O. virosa are visited by diurnal flies, ants, and nocturnal carrion beetles, together with many other occasional visitors. Among them, only the carrion beetles from the genus Phaeochrous were shown to carry pollen of O. virosa. Noctur...

Neural Summation in the Hawkmoth Visual System Extends the Limits of Vision in Dim Light

Most of the world's animals are active in dim light and depend on good vision for the tasks of daily life. Many have evolved visual adaptations that permit a performance superior to that of manmade imaging devices [1]. In insects, a major model visual system, nocturnal species show impressive visual abilities ranging from flight control [2, 3], to color discrimination [4, 5], to navigation using visual landmarks [6-8] or dim celestial compass cues [9, 10]. In addition to optical adaptations that improve their sensitivity in dim light [11], neural summation of light in space and time-which enhances the coarser and slower features of the scene at the expense of noisier finer and faster features-has been suggested to improve sensitivity in theoretical [12-14], anatomical [15-17], and behavioral [18-20] studies. How these summation strategies function neurally is, however, presently unknown. Here, we quantified spatial and temporal summation in the motion vision pathway of a nocturnal hawkmoth. We show that spatial and temporal summation combine supralinearly to substantially increase contrast sensitivity and visual information rate over four decades of light intensity, enabling hawkmoths to see at light levels 100 times dimmer than without summation. Our results reveal how visual motion is calculated neurally in dim light and how spatial and temporal summation improve sensitivity while simultaneously maximizing spatial and temporal resolution, thus extending models of insect motion vision derived predominantly from diurnal flies. Moreover, the summation strategies we have revealed may benefit manmade vision systems optimized for variable light levels [21].

Bats may eat diurnal flies that rest on wind turbines

Bats are currently killed in large numbers at wind turbines worldwide, but the ultimate reason why this happens remains poorly understood. One hypothesis is that bats visit wind turbines to feed on insects exposed at the turbine towers. We used single molecule next generation DNA sequencing to identify stomach contents of 18 bats of four species (Pipistrellus pygmaeus, Nyctalus noctula, Eptesicus nilssonii and Vespertilio murinus) found dead under wind turbines in southern Sweden. Stomach contents were diverse but included typically diurnal flies, e.g. blow-flies (Calliphoridae), flesh-flies (Sarcophagidae) and houseflies (Muscidae) and also several flightless taxa. Such prey items were eaten by all bat species and at all wind turbine localities and it seems possible that they had been captured at or near the surface of the turbines at night. Using sticky traps, we documented an abundance of swarming (diurnal) ants (Myrmica spp.) and sometimes blow-flies and houseflies at the nacelle house. Near the base of the tower the catches were more diverse and corresponded better with the taxa found in the bat stomachs, including various diurnal flies. To evaluate if flies and other insects resting on the surface of a wind turbine are available to bats, we ensonified a house fly (Musca) on a smooth (plastic) surface with synthetic ultrasonic pulses of the frequencies used by the bat species that we had sampled. The experiment revealed potentially useful echoes, provided the attack angle was low and the frequency high (50–75kHz). Hence resting flies and other arthropods can probably be detected by echolocating bats on the surface of a wind turbine. Our findings are consistent with published observations of the behavior of bats at wind turbines and may actually explain the function of some of these behaviors.

Spore dispersal of fetid Lysurus mokusin by feces of mycophagous insects.

The ecological roles and biological mechanisms of zoochory in plants have long been foci in studies of co-evolutionary processes between plants and animals. However, the dispersal of fungal spores by animals has received comparatively little attention. In this study, the dispersal of spores of a selected fetid fungus, Lysurus mokusin, via feces of mycophagous insects was explored by: collecting volatiles emitted by the fungus using dynamic headspace extraction and analyzing them by GC-MS; testing the capacity of mycophagous insects to disperse its spores by counting spores in their feces; comparing the germinability of L. mokusin spores extracted from feces of nocturnal earwigs and natural gleba of the fungus; and assessing the ability of L. mokusin volatiles to attract insects in bioassays with synthetic scent mixtures. Numerous spores were detected in insects' feces, the bioassays indicated that L. mokusin odor (similar to that of decaying substances) attracts diverse generalist mycophagous insects, and passage through the gut of Anisolabis maritima earwigs significantly enhanced the germination rate of L. mokusin spores. Therefore, nocturnal earwigs and diurnal flies probably play important roles in dispersal of L. mokusin spores, and dispersal via feces may be an important common dispersal mechanism for fungal reproductive tissue.

Visual Reliability and Information Rate in the Retina of a Nocturnal Bee

Nocturnal animals relying on vision typically have eyes that are optically and morphologically adapted for both increased sensitivity and greater information capacity in dim light. Here, we investigate whether adaptations for increased sensitivity also are found in their photoreceptors by using closely related and fast-flying nocturnal and diurnal bees as model animals. The nocturnal bee Megalopta genalis is capable of foraging and homing by using visually discriminated landmarks at starlight intensities. Megalopta's near relative, Lasioglossum leucozonium, performs these tasks only in bright sunshine. By recording intracellular responses to Gaussian white-noise stimuli, we show that photoreceptors in Megalopta actually code less information at most light levels than those in Lasioglossum. However, as in several other nocturnal arthropods, Megalopta's photoreceptors possess a much greater gain of transduction, indicating that nocturnal photoreceptors trade information capacity for sensitivity. By sacrificing photoreceptor signal-to-noise ratio and information capacity in dim light for an increased gain and, thus, an increased sensitivity, this strategy can benefit nocturnal insects that use neural summation to improve visual reliability at night.

Life History of Megacerus discoidus (Coleoptera: Bruchidae), a Seedfeeder of Hedge Bindweed, in Southwestern Virginia

The biology of Megacerus discoidus (Say), a potential candidate for the biological control of hedge bindweed, was studied in southwestern Virginia from 1982 to 1984. The beetle has four larval instars, one generation a year, and overwinters as a fourth instar inside the seed. Each larva consumed ca. 40–50% of the seed content before diapause, and the rest of the seed in the following spring. Only one larva can successfully complete development within a seed. Cannibalism was most common among second and third instars. Adults emerge in mid- to late June; they are active diurnal fliers. The females usually oviposit under bracts of the host seedpods and occasionally on flowers. The period of oviposition activity lasts about a month. Good synchronization was observed between life cycle of the insect and phenology of hedge bindweed. An egg parasite, Uscana semifumipennis Girault (Trichogrammatidae), and an external larval parasite, Dinamus sp. (Pteromalidae), were found.