Boric acid toxic sugar bait suppresses male Aedes aegypti (Diptera: Culicidae): wing beat frequency and amplitude, flight activity, fecundity, insemination, and mate-finding Allee effect.

BACKGROUND: Controlling the spread of arboviral diseases remains a considerable challenge due to the rapid development of insecticide resistance in Aedes mosquitoes. This study evaluated the effects of boric acid-containing toxic sugar bait (TSB) on field populations of resistant Aedes aegypti mosquitoes. In addition, this study examined the flight activity and wing beat frequency and amplitude of males and the flight activity, fecundity, and insemination of females after pairing with males exposed to TSB. The population dynamics of Aedes mosquitoes under imbalanced sex ratios were examined to simulate realistic field conditions for male suppression under the effect of TSB. RESULTS: The mortality of male mosquitoes was consistently high within 24 h after exposure. By contrast, the mortality of female mosquitoes was inconsistent, with over 70% mortality observed at 168 h. The flight activity and wing beat amplitude of treated males were significantly lower than those of controls, but no significant difference in wing beat frequency was detected. The fecundity and insemination of treated female mosquitoes were lower than those of controls. A simulation study indicated that considerably low male population densities led to mating failures, triggering a mate-finding Allee effect and resulting in persistently low population levels. CONCLUSION: Boric acid-containing TSB could effectively complement current chemical intervention approaches to control resistant mosquito populations. TSB is effective in reducing field male populations and impairing male flight activity and female-seeking behavior, resulting in decreased fecundity and insemination. Male suppression due to TSB potentially results in a small mosquito population. © 2024 Society of Chemical Industry.

Impact of the annular solar eclipse on December 26, 2019 on the foraging visits of bees.

Solar eclipse has remarkable effect on behavior of animals. South India experienced a 97% magnitude annular eclipse on December 26, 2019 during 08:04-11:04 h with the totality phase appeared during 09:25-09:30 h. We investigated whether the foraging activity of the bees was limited by the eclipse, what bees are affected most, and which part of the eclipse was critical for bee activities to understand how a group of insects that rely the Sun, the sunlight, and the sun rays for their navigation and vision behaves to the eclipse. We opted to watch the bees in their foraging ground, and selected the natural flower populations of Cleome rutidosperma, Hygrophila schulli, Mimosa pudica, and Urena sinuata-some of the bee-friendly plants-to record the visitor richness and visitation rate on the flowers on eclipse and non-eclipse days and during the hour of totality phase and partial phase of the eclipse. Fewer flower-visiting species were recorded on the eclipse day than on the non-eclipse days, but in the period of totality, very few bee species were active, and limited their activity to only one population of C. rutidosperma. Visits of honey bees and stingless bees were affected most, but not that badly of solitary bees and carpenter bees. Bees, particularly the social bees use Sun for navigation and deciphering information on forage sources to fellow workers. The eclipse, like for many other animals, might hamper bees' orientation, vision, and flight.

Effects of nocturnal celestial illumination on high-flying migrant insects.

Radar networks hold great promise for monitoring population trends of migrating insects. However, it is important to elucidate the nature of responses to environmental cues. We use data from a mini-network of vertical-looking entomological radars in the southern UK to investigate changes in nightly abundance, flight altitude and behaviour of insect migrants, in relation to meteorological and celestial conditions. Abundance of migrants showed positive relationships with air temperature, indicating that this is the single most important variable influencing the decision to initiate migration. In addition, there was a small but significant effect of moonlight illumination, with more insects migrating on full moon nights. While the effect of nocturnal illumination levels on abundance was relatively minor, there was a stronger effect on the insects' ability to orientate close to downwind: flight headings were more tightly clustered on nights when the moon was bright and when cloud cover was sparse. This indicates that nocturnal illumination is important for the navigational mechanisms used by nocturnal insect migrants. Further, our results clearly show that environmental conditions such as air temperature and light levels must be considered if long-term radar datasets are to be used to assess changing population trends of migrants. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Continental-scale patterns in diel flight timing of high-altitude migratory insects.

Many insects depend on high-altitude, migratory movements during part of their life cycle. The daily timing of these migratory movements is not random, e.g. many insect species show peak migratory flight activity at dawn, noon or dusk. These insects provide essential ecosystem services such as pollination but also contribute to crop damage. Quantifying the diel timing of their migratory flight and its geographical and seasonal variation, are hence key towards effective conservation and pest management. Vertical-looking radars provide continuous and automated measurements of insect migration, but large-scale application has not been possible because of limited availability of suitable devices. Here, we quantify patterns in diel flight periodicity of migratory insects between 50 and 500 m above ground level during March-October 2021 using a network of 17 vertical-looking radars across Europe. Independent of the overall daily migratory movements and location, peak migratory movements occur around noon, during crepuscular evening and occasionally the morning. Relative daily proportions of insect migration intensity and traffic during the diel phases of crepuscular-morning, day, crepuscular-evening and night remain largely equal throughout May-September and across Europe. These findings highlight, extend, and generalize previous regional-scale findings on diel migratory insect movement patterns to the whole of temperate Europe. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

In the fed state, autophagy plays a crucial role in assisting the insect vector Rhodnius prolixus mobilize TAG reserves under forced flight activity.

Autophagy is a cellular degradation pathway mediated by highly conserved autophagy-related genes (Atgs). In our previous work, we showed that inhibiting autophagy under starvation conditions leads to significant physiological changes in the insect vector of Chagas disease Rhodnius prolixus; these changes include triacylglycerol (TAG) retention in the fat body, reduced survival and impaired locomotion and flight capabilities. Herein, because it is known that autophagy can be modulated in response to various stimuli, we further investigated the role of autophagy in the fed state, following blood feeding. Interestingly, the primary indicator for the presence of autophagosomes, the lipidated form of Atg8 (Atg8-II), displayed 20%-50% higher autophagic activation in the first 2 weeks after feeding compared to the third week when digestion was complete. Despite the elevated detection of autophagosomes, RNAi-mediated suppression of RpAtg6 and RpAtg8 did not cause substantial changes in TAG or protein levels in the fat body or the flight muscle during blood digestion. We also found that knockdown of RpAtg6 and RpAtg8 led to modest modulations in the gene expression of essential enzymes involved in lipid metabolism and did not significantly stimulate the expression of the chaperones BiP and PDI, which are the main effectors of the unfolded protein response. These findings indicate that impaired autophagy leads to slight disturbances in lipid metabolism and general cell proteostasis. However, the ability of insects to fly during forced flight until exhaustion was reduced by 60% after knockdown of RpAtg6 and RpAtg8. This change was accompanied by TAG and protein increases as well as decreased ATP levels in the fat body and flight muscle, indicating that autophagy during digestion, i.e., under fed conditions, is necessary to sustain high-performance activity.

An Inexpensive System to Investigate the Daily Rhythms of Insects.

Insects' daily rhythms occur in response to their surrounding environment. Recognizing the daily rhythms of pathogen vectors can be helpful in developing effective, safe, and sustainable management strategies to control vector insects and reduce the spread of pathogens. However, studying the daily rhythm of insects often requires costly or labor-intensive trapping, and few tools are available to quantify daily rhythms in the field. We developed a simple collection system to study the flight activity of mosquitoes and biting midges using a contained, programmable, rotating, automatic pet feeder. A diverse assemblage of nuisance and vector species were collected with our system, including mosquitoes of the genera Aedes, Anopheles, Culex, and Deinocerites and biting midges (Ceratopogonidae) such as the coastal pest Culicoides furens. Surprisingly, mosquitoes and biting midges were less active during crepuscular periods (1800-2100h; 0600-0900h) than during dark periods (2100h-2400h; 0300h-0600h). A number of urban and agricultural pest insects were captured, including Coleoptera, Hymenoptera, Isoptera and Lepidoptera. This study shows that relatively inexpensive products can be adapted to study the daily rhythms of flying vectors and nuisance arthropods, with implications for vector-borne disease transmission and control. The collection system could also be used with flight intercept or pitfall traps, permitting study of the circadian activity patterns of a diverse array of arthropods.

The evening crepuscular host-seeking activity of Anopheles mosquitoes in northeast Brazil.

Studies on the timing of anopheline host-seeking are important for understanding mosquito ecology, behaviors, and possible role in disease transmission. To study the evening crepuscular host-seeking activity of anophelines and the effects of moonlight, anopheline mosquitoes were collected with light traps settled in a livestock area in the Brazilian Cerrado region. Traps (Silva traps) were placed next to animal enclosures at 1.5 m asl. The research was divided in 2 experiments: the first experiment (12 nights) comprised 2 trapping periods, one from 6 PM to 7 PM and one from 7 PM to 6 AM, and the second experiment (16 evenings) divided in three 20-min intervals based on the 3 twilight phases (civil: 6-6:20 PM; nautical: 6:20-6:40 PM; and astronomical: 6:40-7 PM). A total of 2,815 anopheline mosquitoes and 9 species were found. The main species were Anopheles triannulatus s.l., An. argyritarsis, An. goeldii, and An. evanse. Host-seeking mosquitoes were more frequently active during the first hour after sunset, with a significant peak in the second 20-min interval. After that, a decrease in the number of individuals was observed from the astronomical twilight onwards. Moonlight did not affect the evening flight activity of anophelines. By using LED-based passive light traps, the evening arrival time of anophelines at blood-feeding sites was demonstrated, and it may be a key time window for malaria vector control interventions.

Mosquito community composition in two major stopover aquatic ecosystems used by migratory birds in northern Spain.

Mosquitoes (Diptera: Culicidae) are common bloodsucking Diptera frequently found in aquatic environments, which are valuable ecosystems for many animal species, particularly migrating birds. Therefore, interactions between these animal species and mosquitoes may play a critical role in pathogen transmission. During 2018-2019, mosquitoes were collected from two aquatic ecosystems in northern Spain using different methodologies and identified using classical morphology and molecular tools. A total of 1529 males and females of 22 native mosquito species (including eight new records for the region) were trapped using CO2 -baited Centers for Disease Control and Prevention (CDC) traps and sweep netting. Among the blood-fed female mosquitoes, 11 vertebrate host species-six mammals and five birds-were identified using DNA barcoding. The developmental sites of eight mosquito species were determined across nine microhabitats, and 11 mosquito species were caught landing on humans. The flight period varied among mosquito species, with some peaking in the spring and others in the summer. Our study highlights the advantages of mosquito sampling using various techniques to comprehensively characterise species composition and abundance. Information on the trophic preferences, biting behaviour and influence of climatic variables on the ecology of mosquitoes is also provided.

Effect of ultraviolet LED and trap height on catches of host-seeking anopheline mosquitoes by using a low-cost passive light trap in northeast Brazil.

Light traps have been widely used for monitoring malaria vectors, although drawbacks remain. In this context, new tools and attractants are always becoming available to perform monitoring tasks, like the Silva trap, a passive and low-cost LED-light trap for host-seeking anopheline mosquitoes. In this work, the effectiveness of the Silva trap by using UV-LED and at different heights as well as a comparison with the conventional CDC-type (HP) light trap was studied. A total of 9009 mosquitoes and nine species were caught, Anopheles triannulatus, An. argyritarsis, and An. goeldii being the most frequent species. The green (520 nm) and blue (470 nm) LEDs attracted almost equal numbers of anopheline mosquitoes, but UV LEDs (395 nm) attracted a significantly lower number of individuals (Kruskal-Wallis = 19.68, P = 0.0001). Even with the predominance of mosquitoes trapped at the height of 1.5 m, no significant statistical difference was found among the four heights tested (0.5 m; 1.0 m; 1.5 m; 2.0 m). Green-baited Silva traps collected significantly more individuals than incandescent-baited CDC-type traps (U = 60.5; P = 0.0303). LEDs have been useful as light sources for attracting insect vectors and together with a low-cost trap, as the Silva trap, a feasible alternative to conventional trap-based monitoring Anopheles mosquitoes that can be implemented in the field.

ChIP-seq profiling of H3K4me3 and H3K27me3 in an invasive insect, Bactrocera dorsalis.

Introduction: While it has been suggested that histone modifications can facilitate animal responses to rapidly changing environments, few studies have profiled whole-genome histone modification patterns in invasive species, leaving the regulatory landscape of histone modifications in invasive species unclear. Methods: Here, we screen genome-wide patterns of two important histone modifications, trimethylated Histone H3 Lysine 4 (H3K4me3) and trimethylated Histone H3 Lysine 27 (H3K27me3), in adult thorax muscles of a notorious invasive pest, the Oriental fruit fly Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), using Chromatin Immunoprecipitation with high-throughput sequencing (ChIP-seq). Results: We identified promoters featured by the occupancy of H3K4me3, H3K27me3 or bivalent histone modifications that were respectively annotated with unique genes key to muscle development and structure maintenance. In addition, we found H3K27me3 occupied the entire body of genes, where the average enrichment was almost constant. Transcriptomic analysis indicated that H3K4me3 is associated with active gene transcription, and H3K27me3 is mostly associated with transcriptional repression. Importantly, we identified genes and putative motifs modified by distinct histone modification patterns that may possibly regulate flight activity. Discussion: These findings provide the first evidence of histone modification signature in B. dorsalis, and will be useful for future studies of epigenetic signature in other invasive insect species.

Effect of vibrational mating disruption on flight activity and oviposition to control the grapevine pest, Scaphoideustitanus.

The increasing demand for safe and sustainably produced food is leading to the development of strategies of pest control alternative to chemicals. One innovative method is Vibrational Mating Disruption (VMD) to disrupt insect communication in plants. VMD was proven effective in preventing mating of the grapevine pest Scaphoideus titanus, vector of flavescence dorée. However, the stress induced by VMD on the target species has the potential to influence other crucial aspects of the insect biology and ethology. Therefore, the goal of this study was to understand side effects of VMD on the flight activity and oviposition of S. titanus. The results of our experiments conducted in the greenhouse showed that in the presence of a receptive female, males fly more if exposed to vibrations than in the silent control but not differently from singles males in silence. Surprisingly, we found that also females subjected to VMD fly more than in the silence. Regarding oviposition, we found that mated females exposed to vibrations and single females (unmated) laid significantly fewer eggs than mated females in silence. In conclusion, this study shows the potential of VMD to interfere, besides with mating, with other important biological aspects of the pest species.

Light, flight and the night: effect of ambient light and moon phase on flight activity of pteropodid bats.

Fruit-feeding pteropodid bats roost under varying light conditions. Some roost in trees with high exposure to daylight (> 1000 lx), while others roost in dark caves (< 0.1 lx). To understand the effect of ambient light intensity and moon phase on flight activity, we examined flight times across five lunar cycles in three pteropodid species whose roosts differ in daylight exposure. We found significant interspecific differences in flight emergence and termination times. All species initiated flights after sunset but Rousettus leschenaultii, which typically roosts in caves, delayed emergence (40 ± 11 min) more than the two tree-roosting species Pteropus giganteus (16 ± 6 min) and Cynopterus sphinx (19 ± 7 min). R. leschenaultii terminated flights earlier (30 ± 7 min before sunrise) than P. giganteus (11 ± 11 min) and C. sphinx (16 ± 10 min). All individuals from P. giganteus and C. sphinx roosts emerged within less than an hour, while emergence times were more spread out in the R. leschenaultii colony. Peak emergence times differed across moon phases in the cave-roosting R. leschenaultii but not in the other species. Flight activity in R. leschenaultii is restricted to comparatively lower light levels than the tree-roosting species. The observed interspecific differences suggest that bat species, sharing same landscapes may respond differently to light pollution.

Correlation Between Increased Homing Flight Duration and Altered Gene Expression in the Brain of Honey Bee Foragers After Acute Oral Exposure to Thiacloprid and Thiamethoxam.

Neonicotinoids as thiamethoxam and thiacloprid are suspected to be implicated in the decline of honey bee populations. As nicotinic acetylcholine receptor agonists, they disturb acetylcholine receptor signaling in insects, leading to neurotoxicity and are therefore globally used as insecticides. Several behavioral studies have shown links between neonicotinoid exposure of bees and adverse effects on foraging activity, homing flight performance and reproduction, but the molecular aspects underlying these effects are not well-understood. In the last years, several studies through us and others showed the effects of exposure to neonicotinoids on gene expression in the brain of honey bees. Transcripts of acetylcholine receptors, hormonal regulation, stress markers, detoxification enzymes, immune system related genes and transcripts of the energy metabolism were altered after neonicotinoid exposure. To elucidate the link between homing flight performance and shifts in gene expression in the brain of honey bees after neonicotinoid exposure, we combined homing flight activity experiments applying RFID technology and gene expression analysis. We analyzed the expression of endocrine factors, stress genes, detoxification enzymes and genes linked to energy metabolism in forager bees after homing flight experiments. Three different experiments (experiment I: pilot study; experiment II: "worst-case" study and experiment III: laboratory study) were performed. In a pilot study, we wanted to investigate if we could see differences in gene expression between controls and exposed bees (experiment I). This first study was followed by a so-called "worst-case" study (experiment II), where we investigated mainly differences in the expression of transcripts linked to energy metabolism between fast and slow returning foragers. We found a correlation between homing flight duration and the expression of cytochrome c oxidase subunit 5A, one transcript linked to oxidative phosphorylation. In the third experiment (experiment III), foragers were exposed in the laboratory to 1 ng/bee thiamethoxam and 8 ng/bee thiacloprid followed by gene expression analysis without a subsequent flight experiment. We could partially confirm the induction of cytochrome c oxidase subunit 5A, which we detected in experiment II. In addition, we analyzed the effect of the feeding mode (group feeding vs. single bee feeding) on data scattering and demonstrated that single bee feeding is superior to group feeding as it significantly reduces variability in gene expression. Based on the data, we thus hypothesize that the disruption of energy metabolism may be one reason for a prolongation of homing flight duration in neonicotinoid treated bees.

Spatial Distribution and Flight Patterns of Two Grain Storage Insect Pests, Rhyzopertha dominica (Bostrichidae) and Tribolium castaneum (Tenebrionidae): Implications for Pest Management.

The lesser grain borer, Rhyzopertha dominica, and the rust red flour beetle, Tribolium castaneum, are two major beetle pests commonly found infesting stored products worldwide. Both species can cause severe economic damage and their management is complicated by their potential to develop resistance to several of the limited chemical options available. However, pest management strategies can be improved by understanding the ecology of the pest insect. To determine the spatiotemporal activity of R. dominica and T. castaneum, we conducted a trapping study over two years in a temperate region of south-eastern Australia, with traps located near grain storages and fields. We captured higher numbers of R. dominica than T. castaneum, and both species were more prevalent in traps located close to grain storages. Similar and consistent seasonal patterns were displayed by both species with activity ceasing during the winter (June-August) months. We found linear correlations between maximum daily temperatures and trap catches, and minimum threshold temperatures for flight activity were 14.5 °C and 15.6 °C for R. dominica and T. castaneum, respectively. The results are discussed in relation to the ecology of these pests along with their implications for pest management.

Population Dynamics of Drosophila suzukii in Coastal and Mainland Sweet Cherry Orchards of Greece.

Despite the recent invasion and wide spread of Drosophila suzukii Matsumura (Diptera: Drosophilidae) in Europe, little is known regarding its population trends in coastal areas of the southern Mediterranean countries. Using adult trapping and fruit sampling, we studied the population dynamics of D. suzukii in coastal and mainland (semi-highland) cherry orchards of Greece, from 2018 to 2020. Adults were captured in traps baited with apple cider vinegar, placed in conventional and unmanaged sweet-cherry orchards, and in neighbouring wild growing hosts. Sampling of sweet-cherry fruit to assess infestation levels was conducted from early and late-ripening cherry cultivars in both areas. Adults were captured throughout the year in the coastal area with two peaks registered in spring and late-autumn. Captures were nearly zero during the hot summer months. Flight activity exhibited only one peak in autumn at the mainland area, and ceased during winter and spring. Captures in wild hosts were lower during the sweet-cherry ripening period than later in the season. Higher sweet-cherry infestation levels were recorded in the coastal than in the mainland area and in unmanaged than in commercial orchards. Both early and late-ripening cultivars were highly susceptible to D. suzukii infestation in the coastal area. Infestation rates were higher in late-ripening cultivars than in early-ripening ones in the mainland area. We conclude that D. suzukii has well adapted to the Mediterranean climate of Greece, and is able to progressively exploit several crops and wild hosts of mainland and coastal areas.

Data on winged insect dynamics in melon crops in southeastern France.

This article displays insect count data obtained in eleven field trials conducted between 2010 and 2019 in southeastern France. Winged insect abundances were monitored daily within melon crops during 8-11 weeks in May-July using a suction trap or a yellow pan trap. Aphids were identified under a stereomicroscope. In total, 29,709 winged aphids belonging to 216 taxa and 151,061 other flying insects were caught. Among possible uses, these data can populate larger multisite studies or larger time series investigating aphid community variations. They can also feed generic studies exploring temporal dependencies or species assemblages. They can stimulate new collaborations with entomologists keen on implementing molecular tools or taxonomic expertise on a large specimen collection.

Influence of Temperature and Precipitation Anomaly on the Seasonal Emergence of Invasive Bark Beetles in Subtropical South America.

Several invasive bark beetle species have caused major economic and ecological losses in South America. Accurate predictions of beetle emergence times will make control efforts more efficient and effective. To determine whether bark beetle emergence can be predicted by season, temperature, or precipitation, we analyzed trapping records for three introduced pest species of bark beetles in Uruguay. We used trigonometric functions as seasonal predictors in generalized linear models to account for purely seasonal effects, while testing for effects of temperature and precipitation. Results show that all three beetle species had strong but unique seasonal emergence patterns and responded differently to temperature and precipitation. Cyrtogenius luteus (Blandford) emerged in summer and increased with precipitation but was not affected by temperature. Hylurgus ligniperda (Fabricius) emerged in winter and increased with temperature but was not affected by precipitation. Orthotomicus erosus (Wollaston) had a primary emergence in spring, and a smaller emergence in early summer, but showed no significant relationship with temperature or precipitation. This study shows that the emergence of these bark beetle species in Uruguay is influenced by seasonality more than by temperature and precipitation fluctuations. It also shows how seasonality can be easily incorporated into models to make more accurate predictions about pest population dynamics.

Daily and seasonal variation of muscid flies (Diptera: Muscidae) in Chiang Mai province, northern Thailand.

Flies of the family Muscidae, or muscids, are of medical and veterinary importance worldwide due to their recognition as nuisance pests and myiasis-producing agents. Effective control of muscids requires biological information on population dynamics daily and across seasons. In this study, such patterns were investigated in three different microhabitats (e.g., forest area, palm plantation and longan orchard) in a suburban area of Chiang Mai Province, northern Thailand. Adult fly samplings were conducted for 24-h intervals using semiautomatic traps and 1-day old beef offal as bait. Samplings were carried out twice per month from July 2013 to June 2014. A total of 3,419 muscids were trapped, comprising nine species, with Musca domestica Linnaeus accounting for the majority (n = 1,329; 38.9%) followed by Hydrotaea spinigera Stein (n = 770; 22.5%) and Musca ventrosa Wiedemann (n = 740; 21.7%). The greatest overall abundance was in the longan orchard location (n = 1,508; 44.1%). Community structure peaked during the rainy season (mid-May to mid-Oct). Peak activity during the day was late morning (9.00 to 12.00 h) for M. domestica, early morning (6.00 to 9.00 h) for H. spinigera, and early afternoon (12.00 to 15.00 h) for M. ventrosa. Temperature had no significant effect on the abundance of M. domestica (rs= -0.030, p = 0.576) or H. spinigera (rs = 0.068, p = 0.200), but had a weak negative correlation with M. ventrosa (rs = -0.238, p = 0.0001). Relative humidity had a weak negative correlation with M. domestica (rs = -0.263, p = 0.0001), H. spinigera (rs = -0.107, p = 0.043) and M. ventrosa (rs = -0.344, p = 0.0001). More females (n = 2,078) were trapped than males (n = 761). These results provide baseline information of daily and seasonal dynamic activity of muscid flies under natural conditions, which is the prerequisite information for effective control measures.

Foraging strategies and physiological adaptations in large carpenter bees.

Large carpenter bees are charismatic and ubiquitous flower visitors in the tropics and sub-tropics. Unlike honeybees and bumblebees that have been popular subjects of extensive studies on their neuroethology, behaviour and ecology, carpenter bees have received little attention. This review integrates what is known about their foraging behaviour as well as sensory, physiological and cognitive adaptations and is motivated by their versatility as flower visitors and pollinators. This is evident from their extremely generalist foraging and adeptness at handling diverse flower types as legitimate pollinators and as illegitimate nectar robbers. They purportedly use traplining to forage between isolated patches and are long-distance flyers over several kilometres suggesting well-developed spatial learning, route memory and navigational capabilities. They have a broad range of temperature tolerance and thermoregulatory capabilities which are likely employed in their forays into crepuscular and nocturnal time periods. Such temporal extensions into dim-light periods invoke a suite of visual adaptations in their apposition optics. Thus, we propose that carpenter bees are an excellent though understudied group for exploring the complex nature of plant-pollinator mutualisms from ecological and mechanistic perspectives.

Contrasting response of haematological variables between long-term training and short exercise bouts in zebra finches (Taeniopygia guttata).

Physical aerobic activity is oxygen demanding, but - particularly for birds - there is still little understanding of how blood contributes to oxygen supply under various activity levels. In a two-factorial experimental design, we investigated the long-term effect of daily flight training and the immediate effect of a short exercise bout on a set of haematological variables: haemoglobin (Hb) content, haematocrit (Hct), and red blood cell number (RBCcount) and size (RBCarea) in zebra finches (Taeniopygia guttata). For a period of 6 weeks, birds were either trained daily for 3 h in a flight arena or remained untrained. Subsequently, half of each group was blood sampled either in the resting condition or after a 5 min exercise bout in a flight-hover wheel. We found significantly lower Hb content, Hct and RBCcount compared with that in untrained controls in response to training, while RBCarea did not differ between treatments. Response to an exercise bout revealed the opposite pattern, with significantly higher Hb content and Hct compared with that in non-exercised birds. Additionally, RBCarea was significantly smaller immediately after exercise compared with that in non-exercised birds, and such short-term flexibility represents a novel finding for birds. This contrasting response in erythrocyte characteristics with respect to long-term training and short exercise bouts appears as a clear pattern, presumably underlain by changes in water balance. We infer alterations of blood flow to be involved in adequate oxygen supply. During an exercise bout, RBCarea flexibility may not only enhance oxygen delivery through improved erythrocyte surface area to volume ratio but also improve blood flow through a compensatory effect on blood viscosity.