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.

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.

Diversity patterns of hawkmoths (Lepidoptera: Sphingidae) in the canopy of an ombrophilous forest in Central Amazon, Brazil / Padrões de diversidade de Sphingidae (Lepidoptera) no dossel de floresta ombrófila na Amazônia central, Brasil

ABSTRACT Sphingidae attracted to light were systematically collected in an Amazonian forest canopy. Sampling occurred at a height of 34 m in an upland primary rainforest plateau in the Cueiras River basin, located within the Experimental Station of Tropical Silviculture, Manaus municipality, Amazonas, Brazil. The hawkmoths were collected using a vertical white sheet illuminated by a 250 W mixed mercury light and a 20 W black-light (BLB) fluorescent tube. Monthly collections were carried out from January to December 2004, during three nights of lunar transition from third quarter moon to new moon between 6 p.m. and 6 a.m. We sampled 1748 specimens, represented by 1485 males and 263 females, belonging to 52 species and 21 genera. Xylophanes comprised the highest number of species (seven), followed by Erinnyis, with six species. The most abundant species were Pseudosphinx tetrio (169 specimens), Pachylia darceta (162), Erinnyis ello ello (154), Isognathus excelsior (151) and Callionima parce (139). The species accumulation curve showed that the species richness tended to stabilize by the eighth month. We also observed that species composition altered significantly throughout the night period. All presented hawkmoth records are new for the canopy in the central Amazon.

RESUMO Foram realizadas coletas sistemáticas de Sphingidae no dossel de floresta ombrófila densa na Amazônia central utilizando-se armadilha luminosa. As coletas ocorreram em uma floresta primária de terra firme, na bacia do Rio Cuieiras, a 34 m de altura na torre da Estação Experimental de Silvicultura Tropical, Manaus, Amazonas, Brasil. Foi utilizado um lençol branco iluminado com uma lâmpada de luz mista de mercúrio e uma lâmpada de luz negra UV-BLB. As mariposas foram coletadas mensalmente durante o ano de 2004, em três noites consecutivas de lua minguante e/ou lua nova, sempre das 18:00 às 06:00h. Foram coletados 1748 espécimes, dos quais 769, por serem comuns, foram identificados, marcados e soltos. Foram obtidos 1485 machos e 263 fêmeas, pertencentes a 21 gêneros e 52 espécies. Xylophanes foi representado por sete espécies, seguido por Erinnyis com seis. As espécies mais abundantes foram Pseudosphinx tetrio (169 espécimes), Pachylia darceta (162), Erinnyis ello ello (154), Isognathus excelsior (151) e Callionima parce (139). A curva de acumulação de espécie mostrou que em torno do oitavo mês de coleta, a riqueza de espécies tendeu a estabilizar. Foi possível observar ainda que a composição de esfingídeos mudou significativamente ao longo da noite. Todos os registros são novos para o dossel de floresta na Amazônia central.

Diversidad de cicadélidos y clastoptéridos (Hemiptera) en tres zonas productoras de café afectadas por Xylella fastidiosa Wells et al. en Costa Rica / Hemipteran diversity (Cicadellidae and Clastopteridae) in three coffee production zones affected by Xylella fastidiosa (Wells et al.) in Costa Rica

Se realizó un estudio durante los años 2002, 2003 y 2004, con el fin de determinar la composición, la abundancia, riqueza, diversidad, equidad, ocurrencia y fluctuación temporal de las especies de saltahojas en tres zonas productoras de café de Costa Rica. Se utilizaron trampas amarillas pegajosas para clasificar y cuantificar el número de saltahojas adultos durante el período de muestreo. Se encontró un total de 82.500 individuos, pertenecientes a 139 especies ubicadas dentro de nueve subfamilias. San Isidro de León Cortés presentó la mayor diversidad entre los sitios estudiados. Veinticinco especies se encontraron frecuentemente en al menos uno de los sitios muestreados, y solamente Coelidiana sp.1, Osbornellus sp.1, Scaphytopius sp.1 y Empoasca sp. se capturaron a lo largo de todo el período de estudio. La fluctuación temporal de los taxa que comprenden los principales vectores de X. fastidiosa Wells et al. mostró diferencias entre las zonas estudiadas.

A survey was conducted during 2002, 2003 and 2004 to determine the leafhopper species composition, abundance, richness, diversity, evenness, occurrence and flight activity among three coffee production zones of Costa Rica. Yellow sticky traps were used to qualify and quantify the number of aerial leafhoppers during the sampling period. A total of 82,500 individuals, belonging to 139 species within nine leafhopper subfamilies, were trapped. San Isidro de León Cortés site presented the highest diversity from the three surveyed sites. Twenty five species were frequently trapped at least in one of the studied zones, and only Coelidiana sp.1, Osbornellus sp.1, Scaphytopius sp.1 and Empoasca sp. were trapped throughout the sampling period. The flight activity of the taxa that contain the main vectors of Xylella fastidiosa Wells et al. showed differences among the sampling zones.

Hedylidae (Lepidoptera: Hedyloidea) coletados à luz a 40 metros de altura no dossel da floresta da Estação Experimental de Silvicultura Tropical em Manaus, Amazonas, Brasil / Hedylidae (Lepidoptera: Hedyloidea) collected with light trap at 40 meter height over an Amazon forest canopy at Experimental Station of the Tropical Silviculture in Manaus, Amazonas, Brazil

Os Hedylidae constituem um grupo de lepidópteros exclusivamente neotropical com 35 espécies conhecidas em um gênero, Macrosoma Hübner, 1818. Antes classificados entre as mariposas Geometridae, agora são considerados um grupo basal e noturno de borboletas. Foram realizadas coletas mensais de janeiro a dezembro de 2004 no dossel de uma floresta em área de terra-firme, utilizando um lençol branco iluminado por luz mista de mercúrio e outra luz negra UV-BLB, instalado a 40 m de altura em uma torre. As coletas foram realizadas das 18:00 às 6:00 h do dia seguinte. Foram coletados 55 exemplares , a maioria machos, somente dois exemplares fêmeas pertencentes a nove espécies, uma delas provavelmente nova, a saber: M. hedylaria Warren (1894), M. bahiata (Felder & Rogenhofer, 1875), M. conifera (Warren, 1897), M. heliconiaria (Guenée, 1857), M. hyacinthina (Warren, 1905), M. klagesi (Prout, 1916), M. lucivittata (Walker, 1863) M. nigrimacula (Warren, 1897) e Macrosoma sp. Os Hedylidae foram mais abundantes na estação mais chuvosa, dezembro a maio, com 65,5 por cento dos espécimes coletados. O horário de maior atividade foi entre 19:00 e 22 h com 80 por cento dos espécimes coletados.

The Hedylidae is a lepidopteran group exclusively neotropical, with 35 known species in the genus Macrosoma Hübner, 1818. The family was classified as Geometridae moths but presently they are considered a basal and nocturnal group of butterflies. The collections were carried out monthly from January to December of 2004, during three nights of lunar transition third quarter moon/new moon from 6 p.m. to 6 a.m. The insects were collected over a vertical white sheet illuminated by a 250 watt mixed light and a 20 watt black-light (BLB) lamp installed in a tower at a height of 40 m. We collected 53 male specimens and two female specimens, belonging to nine species of which one was probably new to science: M. hedylaria Warren (1894), M. bahiata (Felder & Rogenhofer, 1875), M. conifera (Warren, 1897), M. heliconiaria (Guenée, 1857), M. hyacinthina (Warren, 1905), M. klagesi (Prout, 1916), M. lucivittata (Walker, 1863) M. nigrimacula (Warren, 1897) e Macrosoma sp. The hedylids were more abundant in the rainy season, December to May, with 65,5 percent of the collected specimens. They were collected mainly from 7:00 pm to 10:00 pm with 80 percent of the collected specimens.

Impacto da precipitação pluviométrica sobre a atividade de vôo de Plebeia remota (Holmberg, 1903) (Apidae, Meliponini) / Rain effect on flight activity of Plebeia remota (Holmberg, 1903) (Apidae, Meliponini)

Através de um sistema automatizado, a atividade do vôo de forrageiras de quatro colônias de Plebeia remota foi registrada ao mesmo tempo, de dezembro de 1998 a dezembro de 1999. Havia uma quantidade grande de dados que permitiram uma análise quantitativa e sazonal do impacto da pluviosidade sobre a atividade de vôo. As colônias vieram de duas localidades diferentes: Cunha, Mata Atlântica de São Paulo e Prudentópolis, Mata Araucária no Paraná. Números percentuais referentes à atividade de vôo para o momento que antecedia em uma hora a chuva, como também durante e após a precipitação, são apresentados. Em todas as colônias observaram-se, predominantemente, decréscimos na atividade externa de P. remota, tanto antes como durante a precipitação. Após cessar a chuva, houve um predomínio de acréscimos, o que indica uma compensação da atividade de vôo em relação ao período chuvoso. De modo geral, o maior decréscimo de atividade de vôo, antes da chuva, ocorreu no outono e o maior acréscimo de atividade de vôo, depois da chuva, ocorreu na primavera. Alterações nesta atividade foram observadas com a variação da intensidade, freqüência e duração das precipitações pluviométricas. A atividade externa foi pouco alterada quando a precipitação foi de até 1,0 mm, mas com o aumento de intensidade, os valores de decréscimo nesta atividade aumentaram. Quando a precipitação ocorreu apenas uma vez por dia, os decréscimos na atividade de vôo foram maiores, comparados às chuvas intermitentes. Chuvas com duração maior que 1 hora causaram decréscimos maiores na atividade de vôo, do que precipitações de curta duração. A atividade do vôo foi bem diferente quando comparados dias com chuva e dias sem chuva, assim como a atividade do vôo foi influenciada diferentemente em dias chuvosos no verão e no inverno. Entretanto, este comportamento não permitiu discriminar as populações.

Through an automated system, foragers' flight activity of four colonies of Plebeia remota was registered simultaneously from December 1998 to December 1999. The large amount of data obtained has allowed a quantitative and seasonal analysis of the rain impact on the bees' flight activity. The colonies came from two different localities: Cunha, Atlantic Rainforest in São Paulo State and Prudentópolis, Araucaria Forest in Paraná State. Percent numbers related to the flight activity for the moment that preceded the rain in one hour, as well as during and after the precipitation are presented. In all colonies, it was observed that the flight activity of P. remota has predominantly decreased before and during the precipitation. After it stopped raining, there was a predominance of increases, what indicates a compensation of flight activity in relation to the rainy period. In general, the greatest decrease of flight activity before rain, occurred in the autumn and the greatest increase of flight activity after rain, occurred in the spring. Alterations in this activity were observed with the variation of intensity, frequency and duration of precipitation. The external activity was little modified when the precipitation was up to 1.0 mm. However, when the rain intensity increased, the bees reduced strongly their flight activity. When the rain occurred only once per day, the decreases in the flight activity were greater, when compared to intermittent rain. Rains that lasted more than one hour caused larger decreases in the flight activity than precipitations of short duration. Flight activity was quite different when we compared days with rain and days without rain, as well as, flight activity was differently influenced in rainy days in the summer and in the winter. However, this behavior (response of flight activity to rain) did not allow to discriminate both populations.

Efeito do vento sobre a atividade de vôo de Plebeia remota (Holmberg, 1903) (Apidae, Meliponini) / Wind effect on flight activity of Plebeia remota (Holmberg, 1903) (Apidae, Meliponini)

Através de um sistema automatizado, a atividade do vôo de forrageiras de quatro colônias de Plebeia remota foi registrada, simultaneamente, de dezembro de 1998 a dezembro de 1999. A grande quantidade de dados obtidos permitiu uma análise quantitativa e sazonal do efeito da velocidade e direção do vento sobre a atividade de vôo. Nas quatro estações, a menor atividade de vôo de Plebeia remota ocorreu quando não houve vento ou quando a velocidade média do vento esteve abaixo de 0,5 m/s. Os picos de atividade de vôo ocorreram em velocidades de vento maiores e variaram segundo as estações e as colônias. No verão, os picos de atividade de vôo estiveram entre 3,5 e 5,5 m/s de velocidade, no outono, na classe 4,0-4,5 m/s, e na primavera entre 4,5 e 6,0 m/s. Entretanto, no inverno, houve clara restrição da atividade externa sob velocidades de vento superiores a 5,5 m/s. As forrageiras de P. remota orientaram preferencialmente seus vôos para certas direções de vento. Exceto no verão, as direções predominantes de vôo foram similares entre as quatro colônias. Estas direções também coincidiram com a posição dos recursos florais mais utilizados pelas colônias. Quando as forrageiras tinham que sair da colônia com vento contra, se registrou menor atividade de vôo.

Through an automated system, foragers' flight activity of four colonies of Plebeia remota was registered at same time from December 1998 to December 1999. The large amount of data obtained allowed a quantitative and seasonal analysis of the effect of speed and direction of wind on their flight activity. In all four seasons, the smallest flight activity of Plebeia remota occurred when there was no wind or when the wind speed average was below 0.5 m/s. The flight activity peaks occurred in higher measured wind speeds and varied according to the seasons and the colonies. In the summer, the flight activity peaks occurred between 3.5 and 5.5 m/s of speed, in the autumn, in the series 4.0-4.5 m/s, and in the spring between 4.5 and 6.0 m/s. In the winter, clear restriction upon flight activity occurred in wind speeds above 5.5 m/s. Plebeia remota foragers guided preferentially their flights for certain wind directions. Except summer, the directions were similar to the four colonies. These directions matched with the locations where the most used floral resources are. On the other hand, lowest flights number coincided with conditions when the foragers would left their colonies upwind.