Acoustic response of the B cell in noctuid moths

Spike activity of the B cell, a unit in the tympanic organ of noctuid moths, was monitored during both stationary flight and acoustic stimulation. This neuron was previously considered (Treat and Roeder, 1959) unresponsive to sound and was thought to be a sensor for thoracic deformations accompanying flight movements. The present study did not reveal changes in B cell spike repetition rate related to active wing flapping, but did reveal a decline in the tonic repetition rate with the onset of an acoustic stimulus. Experimental results indicate that this inhibition of B spike activity is, at least in part, indirect, with the acoustic sense cells serving as the primary receptors. B cell inhibition is most marked with rapidly pulsed, relatively intense bursts of ultrasound. Lowintensity continuous tones evoke little or no change in the B spike repetition rate. The relationship between B spike activity and that of the acoustic sense cells (A cells) is complex. There is roughly an inverse correlation between the two spike activities with the onset and with the cessation of an acoustic stimulus, but B spike activity changes during the stimulus with no concomitant change in A cell spike activity. The possible significance of this complex functioning is considered in relation to avoidance behaviour in flying moths.     

Species traits predict island occupancy in noctuid moths

Knowing how species’ traits relate to processes that underlie occupancy patterns such as colonisation and population persistence, is important for our understanding of how species survive in fragmented and changing landscapes. We used automatic UV light-traps to sample noctuid moths on two remote islands, and compared traits of island occupants with those of a species pool from mainland southeast Sweden. Widely distributed species, generalist species, species with a long adult activity period and species active late in the summer had higher probability of occupancy on the remote islands. The results were consistent between islands. The traits of host plant specificity and species with an adult activity period during late summer remained robust and were statistically significant after controlling for any possible phylogenetic bias. This indicates that species exhibiting those traits survive better when habitat and climate changes. It is crucial to include our results in; (1) conservation planning, e.g. when devising conservation measures in fragmented landscapes; (2) for predictions of future occupancy patterns; and (3) ecosystem impact assessments, e.g. the importance of moths as pollinators, herbivores and being the functional link between parasitoids, plants, consumers and predators.     

Mobility is related to species traits in noctuid moths

1. Mobility is important for the understanding of how species survive in fragmented landscapes and cope with increasing rates of habitat and climate change. However, mobility is a difficult trait to explore and is poorly known in most taxa. Species traits have been studied in relation to range shifts, extinction risks, and responses to habitat area and isolation, and have also been suggested as good estimators of mobility. Here we explore the relation between mobility and species traits in noctuid moths. 2. We sampled noctuid moths by an automatic light‐trap on an island far out in the Baltic Sea. We compared traits of the non‐resident species on the island with traits of a species pool of assumed potential migrants from the Swedish mainland. 3. Mobility was significantly related to adult activity period, length of flight period, and the interaction between host‐plant specificity and distribution area. Widely distributed host‐plant generalists were more mobile than host‐plant specialists with more restricted distribution, and species with an adult activity period in August to September moved to the island to a higher extent than species with an adult activity period in May to July. Our results remained qualitatively robust in additional analyses, after controlling for phylogeny and including all species recorded on the island, except for the trait ‘length of flight period’. 4. Our results highlight the importance of the relation between mobility and species traits. Noctuid moths with certain traits move over longer distances than earlier known. This finding is important to include when predicting range dynamics in fragmented and changing landscapes, and when conservation measures of species are devised.     

Trapping noctuid moths with synthetic floral volatile lures

Male and female noctuid moths were collected from plastic bucket traps that were baited with different synthetic floral chemicals and placed in peanut fields. Traps baited with phenylacetaldehyde, benzyl acetate, and a blend of phenylacetaldehyde, benzyl acetate, and benzaldehyde collected more soybean looper moths, Pseudoplusia includens (Walker), than benzaldehyde-baited or unbaited traps. Females comprised over 67% of the moths captured and most were mated. At peak capture, over 90 male and female moths per night were collected. In another experiment, phenylacetaldehyde delivered in plastic stoppers attracted more P. includens moths than traps baited using other substrates, but this chemical delivered in wax attracted more velvetbean caterpillar moths (Anticarsia gemmatalis Hübner). Other noctuid male and female moths collected included Agrotis subterranea (F.), Argyrogramma verruca (F.), Helicoverpa zea (Boddie), and several Spodoptera species. Aculeate Hymenoptera were collected in large numbers, especially in traps baited with phenylacetaldehyde delivered from stoppers.     

冀西北坝上地区的夜蛾科昆虫

系统调查研究冀西北坝上农牧交错带的鳞翅目Lepidoptera,夜蛾科Noctuidae蛾类,已知11亚科71属117种,并对其多样性做了分析。各月份蛾类组成及数量差异较大,从5月到9月蛾类多样性指数、物种丰富度和个体数基本呈上升趋势,多样性指数与均匀度(r=0.9943)、丰富度(r=0.8979)相一致。而不同月份间的蛾类相似程度差异较大。     

Responses to acoustic stimulation of thoracic interneurons in noctuid moths

In noctuid moths several types of thoracic interneurons process information from the A1 acoustic sense cell. The most frequently encountered types are repeaters and pulse markers. The present study shows that these interneurons belong to one of two physiological categories: ‘stable followers’ which are capable of following pulse repetition rates greater than 10 Hz, and ‘labile followers’ which respond erratically at a pulse repetition rate of 3 Hz and fail entirely when the rate reaches 5 Hz. A rôle for the labile followers in the avoidance flight response is discussed.     

Auditory changes in noctuid moths endemic to a bat-free habitat

If the ears of moths exist primarily to detect the echolocation calls of hunting bats, endemic moths in bat-free areas (i.e., species that have evolved in the absence of the selection pressure maintaining ears) should exhibit signs of deafness. Noctuid moths from the Pacific islands of French Polynesia, a site that has never possessed bats, were sampled and electrophysiologically analysed to test this hypothesis. The auditory sensitivities of seven endemic and twelve immigrant species, captured from the islands of Tahiti, Moorea, and Hiva Oa, were compared. Both classes possess neurally responsive ears, but endemics are significantly deafer than immigrants at frequencies above 35 kHz. This form of deafness is similar to other moths presumably released from the selection pressure of bat predation. I conclude that endemic moths at this site exhibit preliminary stages of deafness and that, considering their small cellular investment, ears in moths will be lost at a slower rate than more complex sensory organs.     

Population dynamics of noctuid moths and damage forecasting in sugar beet

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Size, peripheral auditory tuning and target strength in noctuid moths

We investigated relationships among body size, the frequency of peak auditory sensitivity (best frequency) and acoustic conspicuousness (measured as target strength) to simulated bat echolocation calls in a range of tympanate moths (Lepidoptera: Noctuidae). Audiograms of Amphipyra pyramidea Linnaeus, Agrotis exclamationis Linnaeus, Omphaloscelis lunosa Haworth and Xestia xanthographa Denis and Schiffermüller are described for the first time. Best frequency was inversely related to forewing length, an index of body size. Models predict that target strength falls off rapidly once wavelength (1/frequency) exceeds some defined feature of target size (e.g. circumference for spheres). We investigated how target strength varies in relation to target size and emitted frequency for simple targets (paper discs) and for moths. Target strength fell rapidly when target radius/wavelength < 2 for paper discs of similar size to many noctuid moths. Target strength fell rapidly below wing‐length/wavelength ratios of 2 in relatively small (O. lunosa, wing‐length = 15.2 ± 0.4 mm, best frequency = 45 kHz) and large (N. pronuba, wing‐length = 24.6 ± 0.8 mm, best frequency = 15 kHz) noctuid species, and decreased rapidly at frequencies below 25 kHz in both species. These target strengths were used to predict the detection distance of the moths by bat sonar between 10 and 55 kHz. Predicted detection distances of both species were maximal for fictive call frequencies of 20 kHz, and were reduced at lower frequencies due to decreased target strength and at higher frequencies by excess atmospheric attenuation. Both relatively large and small noctuid moths are therefore strong acoustic targets to bats that echolocate at relatively low frequencies. Bats may emit allotonic calls at low frequency because the costs of reduced detection range are smaller than the benefits of reduced audibility to moths. Because best frequency scales with body size and maximum detection distance is not very sensitive to body size, noctuid moths in the size range examined do not necessarily have best frequencies that would match the call frequencies of bats that may detect the moths at greatest distance precisely. Hence, best frequency may be constrained in part by body size.     

Variable coloration is associated with dampened population fluctuations in noctuid moths

Theory and recent reviews state that greater genetic and phenotypic variation should be beneficial for population abundance and stability. Experimental evaluations of this prediction are rare, of short duration and conducted under controlled environmental settings. The question whether greater diversity in functionally important traits stabilizes populations under more complex ecological conditions in the wild has not been systematically evaluated. Moths are mainly nocturnal, with a large variation in colour patterns among species, and constitute an important food source for many types of organisms. Here, we report the results of a long-term (2003–2013) monitoring study of 115 100 noctuid moths from 246 species. Analysis of time-series data provide rare evidence that species with higher levels of inter-individual variation in colour pattern have higher average abundances and undergo smaller between-year fluctuations compared with species having less variable colour patterns. The signature of interspecific temporal synchronization of abundance fluctuations was weak, suggesting that the dynamics were driven by species-specific biotic interactions rather than by some common, density-independent factor(s). We conclude that individual variation in colour patterns dampens population abundance fluctuations, and suggest that this may partly reflect that colour pattern polymorphism provides protection from visually oriented predators and parasitoids.     

Life‐history traits and climatic responsiveness in noctuid moths

Emergence phenology has been shown to advance considerably in the past decades in many lepidopterans. Noctuid moths (Noctuidae) constitute a species‐rich family of lepidopterans with a large diversity of life history traits presumably driving climatic responsiveness. In our study we aim to assess the role of life‐history and ecological traits in climatic responsiveness of noctuid moths, whilst controlling for phylogenetic dependence. We used a long‐term dataset of European noctuid moths collected from a light‐trap in northeastern Hungary. As the study site is located at the intersection of several biogeographical zones harbouring a large number of noctuid moth species, our dataset provides a unique possibility to investigate the moths’ climatic sensitivity. To estimate the role of life‐history traits and ecological factors in driving lepidopterans’ response to climatic trends, we employed three proxies related to the species’ ecology (habitat affinity, food plant specialization and food type) and two robust types of life‐history traits (migration strategy and hibernation form). The degree of temporal shifts of various measures of emergence phenology was related to hibernation stage, food type and migration strategy. Large‐scale phylogenetic relatedness exerted little constraint in all models fitted on each measure of phenology. Our results imply that noctuid moths overwintering as adults exhibited greater degrees of phenological shifts than species hibernating as larvae or pupae. It implies that moths hibernating as adults are forced to suspend activity in our climate and the prolongation of autumn activity might be the result of increased plasticity in flight periods.     

Convergent patterns of long-distance nocturnal migration in noctuid moths and passerine birds

Vast numbers of insects and passerines achieve long-distance migrations between summer and winter locations by undertaking high-altitude nocturnal flights. Insects such as noctuid moths fly relatively slowly in relation to the surrounding air, with airspeeds approximately one-third of that of passerines. Thus, it has been widely assumed that windborne insect migrants will have comparatively little control over their migration speed and direction compared with migrant birds. We used radar to carry out the first comparative analyses of the flight behaviour and migratory strategies of insects and birds under nearly equivalent natural conditions. Contrary to expectations, noctuid moths attained almost identical ground speeds and travel directions compared with passerines, despite their very different flight powers and sensory capacities. Moths achieved fast travel speeds in seasonally appropriate migration directions by exploiting favourably directed winds and selecting flight altitudes that coincided with the fastest air streams. By contrast, passerines were less selective of wind conditions, relying on self-powered flight in their seasonally preferred direction, often with little or no tailwind assistance. Our results demonstrate that noctuid moths and passerines show contrasting risk-prone and risk-averse migratory strategies in relation to wind. Comparative studies of the flight behaviours of distantly related taxa are critically important for understanding the evolution of animal migration strategies.     

Immunolocalization of odorant-binding proteins in noctuid moths (Insecta, Lepidoptera)

Odorant-binding proteins were studied in the noctuid moths Agrotis segetum, Autographa gamma, Helicoverpa armigera, Heliothis virescens and Spodoptera littoralis using antisera raised against the pheromone-binding protein (PBP) and general odorant-binding protein 2 (GOBP2) of Antheraea polyphemus (Saturniidae). Proteins immunoreacting with these antisera were only found on the antennae and PBP and GOBP2 could be identified on western blots of males and females of all five species. PBPs were predominantly localized in sensilla trichodea and GOBP2 in sensilla basiconica, in good correlation with the stimulus specificity of the receptor cells in these sensilla. In H. armigera and H. virescens the majority of the s. trichodea immunoreacted with the antiserum against PBP of A. polyphemus; in A. segetum, A. gamma and S. littoralis, on the other hand, a high percentage of s. trichodea remained unlabelled. Probably, the PBP expressed in these sensilla is so different that it does not immunoreact with the antiserum used. Such a protein was found by native PAGE of antennal extracts of A. segetum and S. littoralis. These data correlate with the fact that the two heliothine species use pheromones with the same alkyl chain length as A. polyphemus, while the other three species use pheromones with shorter chains. In H. armigera, H. virescens, A. gamma and S. littoralis female antennae were also immunolabelled and a large number of PBP-expressing s. trichodea was consistently found. In S.littoralis this fits with the electrophysiologically recorded high pheromone sensitivity of female s. trichodea, whereas in females of H. armigera and H. virescens no or only weak responses to pheromone stimulation have been reported. Therefore, PBP expression in a sensillum does not necessarily imply pheromone sensitivity of its receptor cells.     

"From freeze with moths": first discovery of a habitat in Andean salars for noctuid moths

Noctuid moths flutter in the high Andes nights at 4,000 m. s. n. m. Their larvae feed on aerial or underground parts of succulent plants. Many of these species are new to science. Strategies and adaptations of the moths for survival in the high Andes mountains are: a circulatory system that includes an abdominal thoracic countercurrent heat exchanger, and they are insulated from the environment by a coat of dense hair like scales. Recently, during January and July 2004, in the northern desert of Chile, called Salar de Punta Negra, under the salt crust we found a large number of pupae and larvae that correspond to three new species of noctuid moth - this pupation site is located in a 10 m wide area surrounding a water body; the mean observed density is 13 to 15 pupae per 100 cm(2). This is a new extreme habitat conquered by noctuid moths.