Nocturnal Moth Species Research Articles

Regional Pollination Activity by Moth Migration in Athetis lepigone.

Nocturnal moths (Lepidoptera) are important pollinators of a wide range of plant species. Understanding the foraging preferences of these insects is essential for their scientific management. However, this information is lacking for most moth species. The present study was therefore conducted to delineate the host plant feeding and pollination ranges of an agriculturally important nocturnal moth species Athetis lepigone by identifying the pollen species adhering to their bodies during long-distance migration. Pollen grains were dislodged from 1871 A. lepigone migrants captured on Beihuang Island in the Bohai Strait between 2020 and 2021. This region is a key seasonal migration pathway for A. lepigone in northern China. Almost 20% of all moths sampled harbored pollens, providing direct evidences that this moth species may serve as pollinators. Moreover, at least 39 pollen taxa spanning 21 plant families and 31 genera were identified, with a preference for Asteraceae, Amaranthaceae, and Pinaceae. Additionally, the pollen adherence ratios and taxa varied with moth sex, inter-annual changes, and seasonal fluctuations. Most importantly, the pollen taxa were correlated with insect migration stages and indicated that A. lepigone bidirectionally migrates between central China (Shandong, Hebei, and Henan Provinces) and northeastern China (Liaoning Province). Overall, the findings of the present work provide valuable information on the pollination behavior, geographical origins, and pollination regions of A. lepigone moths and could facilitate the design and optimization of efficacious local and regional management strategies for this important insect.

Pollen Molecular Identification from a Long-Distance Migratory Insect, Spodoptera exigua, as Evidenced for Its Regional Pollination in Eastern Asia.

Understanding plant-insect interactions requires the uncovering of the host plant use of insect herbivores, but such information is scarce for most taxa, including nocturnal moth species, despite their vital role as herbivores and pollinators. In this study, we determined the plant species visited by an important moth species, Spodoptera exigua, by analyzing attached pollen on migratory individuals in Northeast China. Pollen grains were dislodged from 2334 S. exigua long-distance migrants captured between 2019 and 2021 on a small island in the center of the Bohai Strait, which serves as a seasonal migration pathway for this pest species, and 16.1% of the tested moths exhibited pollen contamination, primarily on the proboscis. Subsequently, 33 taxa from at least 23 plant families and 29 genera were identified using a combination of DNA barcoding and pollen morphology, primarily from the Angiosperm, Dicotyledoneae. Moreover, the sex, inter-annual, and seasonal differences in pollen adherence ratio and pollen taxa were revealed. Notably, compared to previously reported pollen types found on several other nocturnal moths, we found that almost all of the above 33 pollen taxa can be found in multiple nocturnal moth species, providing another important example of conspecific attraction. Additionally, we also discussed the indicative significance of the pollen present on the bodies of migratory individuals for determining their migratory route. Overall, by delineating the adult feeding and pollination behavior of S. exigua, we advanced our understanding of the interactions of the moths with their host plants, and its migration pattern, as well as facilitated the design of (area-wide) management strategies to preserve and optimize ecosystem services that they provide.

Fauna of nocturnal moth species collected in a semi-natural grassland at Kanpu-zan in northern Japan.

Semi-natural grasslands, which house species-rich ecosystems, have rapidly declined since the twentieth century due to land-use practices, such as agricultural intensification and abandonment. Owing to their diversity and known habitat associations, nocturnal moths are considered as one of the most suitable organisms to be studied for assessing the dynamics of species composition as a result of changes in landscape management of semi-natural grasslands. The present study provides the foremost description of nocturnal moth fauna of the semi-natural grassland at Kanpu-zan, northern Japan. Moth population data from 1987 were compared to the data collected in 2018 to evaluate the impact of decline in grasslands on species-richness. During the field sampling in 2018, a total of 226 nocturnal moth species were detected, which was nearly two-thirds of the number of species recorded in 1987, i.e. 396 species. The values obtained in 2018 were found to be nearly constant for different sites. For both periods, it was evident that moth fauna in Kanpu-zan mainly consisted of species that relied on woody plants. Amongst the species which were only recorded in 1987, 107 species were generalists that fed on plants that are commonly distributed in Kanpu-zan. No moth species were recorded that depended upon endangered or extinct plant food sources. Thus, it is unlikely that the decline in the number of moth species in Kanpu-zan was due to the loss in plant food sources. Our results suggest that environmental factors other than food plants may have caused decline and changes in nocturnal moth fauna. More studies on various organism fauna are needed for understanding the conservation of semi-natural grassland, considering that the loss of semi-natural grasslands is one of the major threats to biodiversity.

The dark side of Lepidoptera: Colour lightness of geometrid moths decreases with increasing latitude

AbstractAimThe observed decrease in insect colour lightness with increasing latitude has been explained in earlier macroecological studies by the increased solar absorption of dark coloration, which allows extended periods of activity. However, melanin‐based dark coloration also protects against pathogens and ultraviolet radiation, which select for dark coloration at low latitudes where these selection pressures intensify. In nocturnal insects, the relative importance of these protective functions of dark coloration is expected to surpass thermoregulatory functions, as nocturnal species cannot benefit from extended periods of activity during the daytime. Hence, we expected that diurnal and nocturnal insects show contrasting geographical patterns of colour lightness. We tested these predictions using geometrid moths, which comprise both diurnal and nocturnal species.LocationWestern Palearctic.Time periodContemporary.Major taxa studiedGeometridae (Lepidoptera).MethodsWe used digital image analysis to assess the colour lightness of 637 species, compiled their distribution across 3,777 grid cells of 50 km × 50 km and calculated the assemblage‐based average colour lightness. We used multiple regressions, autoregressive error models and randomizations to test for relationships between colour lightness and environmental variables associated with the thermal environment, putative pathogen pressure and ultraviolet radiation.ResultsWe found a clear decrease in colour lightness of assemblages of both diurnal and nocturnal moth species with increasing latitude. In every model, solar radiation was the most important predictor of colour lightness; that is, colour lightness consistently increased with increasing solar radiation.Main conclusionsThese results indicate that the thermal environment is the most influential climatic driver of insect colour lightness—independent of thermoregulatory strategy and nocturnal or diurnal activity. This challenges the view that extended periods of activity are the main selection pressure for geographical variation in insect colour lightness. Consequently, the relationship between insect colour lightness and the thermal environment might be more general than previously thought.

Reduced mobility but high survival: thermal tolerance and locomotor response of the specialist herbivore, Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae), to low temperatures.

Disentangling the responses of insects to variations in their thermal environment is central to our understanding of the evolution of temperature-dependent performance in these species. Here, we report results of experiments examining the effects of high (upper lethal temperature = ULT) and low (lower lethal temperature = LLT) temperature and exposure time on the survival of larvae and adults of a multivoltine, nocturnal moth species, Pareuchaetes insulata, a biological control agent whose impact on an invasive weed, Chromolaena odorata has been variable in South Africa. The influence of temperature and acclimation on locomotion performance of the moth was also investigated. Temperature and duration of exposure significantly affected survival of both adults and larvae of P. insulata with more extreme temperatures and/or longer durations proving to be more lethal. Third instar larvae and adults are both freeze intolerant and had LT50 of -5.9 and -4.7°C, respectively, after a 2 h exposure. Although cold acclimation was beneficial to the nocturnal larvae, temperatures below 10°C significantly reduce their locomotion activities. The average daily minimum temperatures in the coldest months at three locations in South Africa are over 5°C lower than those of Fort Lauderdale, Florida, USA, where P. insulata was originally collected. Our results suggest that lethal high or low temperatures at short timescales are trivial in explaining the variable performance of P. insulata, but reduced locomotion at sub-lethal temperatures may be an important driver of the population dynamics of the biocontrol agent (especially in winter months) and may consequently explain the low population levels of the moth because of possible reduced feeding by larvae during night-time low temperatures.

Dim Light During Scotophase Enhances Sexual Behavior of the Oriental Tobacco BudwormHelicoverpa assulta(Lepidoptera: Noctuidae)

The role of light in sexual behavior of lepidopteran species has been studied for many years because of the wide variation in the habits of moths and butterflies. Light level is important for mating of butterflies, but information on the potential role of light on sexual behavior in nocturnal moths is scanty. This study was conducted to determine the relationship between light intensity and sexual behavior in a nocturnal moth species. The mating frequency and the hourly variations of both calling behavior and sex pheromone titer in the oriental tobacco budworm Helicoverpa assulta (Guenee) (Lepidoptera: Noctuidae) were determined under several light intensities (0.0, 0.5, 5.0, and 50.0 lux). We found that 1) high-intensity light (50.0 lux) suppressed calling behavior, pheromone production, and mating; 2) low-intensity light (0.5 lux) significantly promoted female calling and mating in less time (1 h) than in complete darkness (0.0 lux); and 3) no relationship existed between sex pheromone production and calling behavior. These results suggested that low-intensity light (0.5 lux) promoted mating. This study provides reliable background information for using sex pheromones in conjunction with light traps for integrated management of nocturnal moths.

Unexpected dynamic up-tuning of auditory organs in day-flying moths.

In certain nocturnal moth species the frequency range of best hearing shifts to higher frequencies during repeated sound stimulation. This could provide the moths with a mechanism to better detect approaching echolocating bats. However, such a dynamic up-tuning would be of little value for day-flying moths that use intra-specific acoustic communication. Here we examined if the ears of day-flying moths provide stable tuning during longer sound stimulation. Contrary to our expectations, dynamic up-tuning was found in the ear of the day-flying species Urania boisduvalii and Empyreuma pugione. Audiograms were measured with distortion-product otoacoustic emissions (DPOAEs). The level of the dominant distortion product (i.e. 2f1-f2) varied as a function of time by as much as 45dB during ongoing acoustic stimulation, showing a systematic decrease at low frequencies and an increase at high frequencies. As a consequence, within about 2s of acoustic stimulation, the DPOAEs audiogram shifted from low to high frequencies. Despite the up-tuning, the range of best audition still fell within the frequency band of the species-specific communication signals, suggesting that intra-specific communication should not be affected adversely. Up-tuning could be an ancestral condition in moth ears that in day-flying moths does not underlie larger selection pressure.

InvasiveSilene latifoliaMay Benefit from a Native Pollinating Seed Predator,Hadena ectypa, in North America

The acquisition of new mutualists and escape from enemies are often essential for the establishment of invasive species. With its introduction to North America, Silene latifolia successfully escaped a number of generalist and specialist enemies, including the seed predator/specialist pollinator Hadena bicruris, but information regarding the acquisition of new mutualists in a community context has not been examined. We used field observations of mixed species arrays and laboratory feeding trials and compared floral scent and plant/pollinator morphological match to explore the interaction in North America of the invasive S. latifolia with the native pollinating seed predator, Hadena ectypa, in order to understand mechanisms of enemy release and mutualist facilitation underlying the successful invasion of S. latifolia. In mixed arrays, H. ectypa visited S. latifolia at a low frequency similar to the combined visitation of other non-Hadena nocturnal moth species. Differences in the floral scent profiles of S. latifolia and Silene stellata, a native coflowering congener and natural host of H. ectypa, combined with the lack of morphological match between H. ectypa and S. latifolia, likely contribute to these results. In the field study, only one H. ectypa egg was oviposited on S. latifolia, and this did not result in a successful fruit attack. Larvae feeding trials in the lab showed no initial feeding preference for pistils of either Silene species. Therefore, our study suggests that S. latifolia has escaped the cost of seed predation typically associated with visitation and oviposition by Hadena pollinators, a potential natural enemy, while taking advantage of pollination services provided by both H. ectypa and other native North American nocturnal moth pollinators.

How Do Acoustic Inputs to the Central Nervous System of the Bollworm Moth Control Its Behavior?

The nervous system of the bollworm moth, Heliothis zea (Boddie), a noctuid moth that is a major pest of cotton, corn, and tomatoes, is served by two pairs of acoustic sense cells. The moths use the acoustic receptors to detect the ultrasonic cries of predatory bats that feed on these moths. Bats use pulsed high frequency sounds to echolocate and capture moths for food. The moths have developed an avoidance behavioral reaction that protects them from predatory bat capture when they detect the echolocating cries of the bats. A pair of acoustic receptors are located in each tympanic organ located on the lateral wall of the metathorax on each side of the moth. A1 receptor, the most sensitive unit, can detect 20 kilohertz frequencies at sound pressure levels of 35 dB (0 dB re 20 @m Pa). The A2 receptor is about 20 dB less sensitive and is also tuned to be most sensitive to 20 kHz sounds. Pulse rates of 10/sec and pulse durations of 10 msec were most effective for eliciting evasive reactions in the bollworm moth. In field and laboratory behavior tests, we have determined that the moths can detect 85 dB pulses of ultrasound (20 kHz) at a distance of 50-80 feet from the moth and after detection the moths make evasive reactions. My recent research has focused on identification of the neural circuits from the acoustic receptors to and through the central nervous system (meso- metathoracic ganglia and prothoracic ganglion and brain) to the motor nerves responsible for executing the evasive reactions. The structure of the various parts of the circuits responsible for the behavioral reactions have been identified using histochemical techniques (cobalt chloride and lucifer yellow) that mark only the axons carrying the acoustic information (action potentials) and the motor nerve commands from these nerves to the muscles responsible for directed flight. Electrophysiological techniques were used to monitor the information flow in the acoustic axons that feed the moth coded information on the high frequency sounds in its environment. If the information is from the A1 receptor, it is processed in the to produce behavior commands that are transmitted by the motor nerves to generate a behavioral reactions that produce turn reactions. The information from the A2 receptor is transmitted to neurons in the mesothoracic ganglion directly and produce rapid unpredictable evasive reactions (spirals, dives, and cessation of flight) and do not require brain processing. The anatomical circuits, behavioral reaction times, and electrophysiological monitoring of neural activities confirm these findings. These and other studies have demonstrated that the behavior of the moth is influenced or controlled by sensory inputs that can have positive and negative effects on the moth behavior. When the flying moth is attracted to an ultraviolet light and a sound source at the light source generates a pulses of high frequency sound, the moth will make an evasive reaction to the sound stimuli in preference to the continued attraction to the visual stimuli. In other instances, another nocturnal moth species that is attracted to a sex pheromone (an olfactory attractant) can be terminated (behavior turned off) if the trap containing the pheromone is constructed of specific colors that cause an avoidance reaction to the visual stimuli that are dominant over the attractive odor. These model acoustic studies are establishing the boundaries and conditions that must be met in the neural circuits of the central nervous system of the moth for specific sensory stimuli to be functionally effective. Normal or usual behaviors can be turned on and off when the proper sensory stimuli are presented according to specific criterion conditions. To obtain maximum benefits from the use of non-insecticidal technologies to control insects, a full understanding of the levels of neural processing of sensory stimuli is needed, as is an understanding of the spheres and levels of dominance that specific sensory stimuli exert in the control of the behavior of the insect pest.

Short-range precopulatory behavior of males of Pectinophora gossypiella (Lepidoptera:Gelechiidae)

The short-range precopulatory behavior of males of Pectinophora gossypiella was examined by direct observation and sequential photography. A pheromone-stimulated male takes flight and moves upwind toward a pheromone-releasing female. He usually lands several centimeters from her and then walks toward her while fluttering his wings and extending his hairpencils. The female typically withdraws her pheromone gland when the male first contacts her. The male makes a copulatory attempt and, if coupling occurs, he moves to an “end-to-end” position. Males oriented toward a synthetic pheromone source even in the absence of visual stimuli from a female, and their forward locomotion was usually arrested when they arrived at the source. Copulatory attempts were then sometimes directed toward the source. In the presence of pheromone, three-dimensional female models were much more effective than the pheromone source alone in eliciting copulatory attempts. Downwind models showed decreasing abilities to elicit male precopulatory responses with increasing distances from the source. However, increasing the amount of pheromone at the source resulted in an increase in the percentage of responses occurring at the furthest downwind models. The various components of precopulatory behavior observed for P. gossypiella are compared and contrasted with the published records of similar behaviors in other nocturnal moth species.