Experimental evidence for male biased flight-to-light behavior in two moth species

Many studies report a greater abundance of male than female moths in light trap catches. The finding was interpreted as evidence for male-biased attraction to light, but alternatives could not be ruled out. For example, it is not known, how much the sex ratio in the catches deviates from the natural sex ratio. To overcome these limitations, we experimentally tested the flight-to-light behavior of two moth species, Yponomeuta cagnagella (Hübner) (Lepidoptera: Yponomeutidae) and Ligdia adustata (Denis and Schiffermüller) (Lepidoptera: Geometridae), under standardized conditions in an enclosed environment. In our test, we controlled the sex ratio, age, and population size. We recorded the moths caught in the trap and those that remained outside. Depending on the species, between 27 and 72% of all moths were caught in the light trap. We found that male moths were significantly and about 1.6 times more frequently attracted to the light than female moths. Our results were consistent for both species and hold good on the level of populations. We experimentally supported the general observation of a sexual dimorphism in the flight-to-light behavior of moths. Possible functional explanations include different flight activities of males and females or differences in the perception of light between males and females. Our experimental demonstration of a sexual dimorphism in the flight-to-light behavior of moths together with the common observation of an overrepresentation of males in light traps and other artificial light sources has implications for population and conservation biology.     

Artificial light at night causes diapause inhibition and sex‐specific life history changes in a moth

Rapidly increasing levels of light pollution subject nocturnal organisms to major alterations of their habitat, the ecological consequences of which are largely unknown. Moths are well‐known to be attracted to light at night, but effects of light on other aspects of moth ecology, such as larval development and life‐history, remain unknown. Such effects may have important consequences for fitness and thus for moth population sizes. To study the effects of artificial night lighting on development and life‐history of moths, we experimentally subjected Mamestra brassicae (Noctuidae) caterpillars to low intensity green, white, red or no artificial light at night and determined their growth rate, maximum caterpillar mass, age at pupation, pupal mass and pupation duration. We found sex‐specific effects of artificial light on caterpillar life‐history, with male caterpillars subjected to green and white light reaching a lower maximum mass, pupating earlier and obtaining a lower pupal mass than male caterpillars under red light or in darkness. These effects can have major implications for fitness, but were absent in female caterpillars. Moreover, by the time that the first adult moth from the dark control treatment emerged from its pupa (after 110 days), about 85% of the moths that were under green light and 83% of the moths that were under white light had already emerged. These differences in pupation duration occurred in both sexes and were highly significant, and likely result from diapause inhibition by artificial night lighting. We conclude that low levels of nocturnal illumination can disrupt life‐histories in moths and inhibit the initiation of pupal diapause. This may result in reduced fitness and increased mortality. The application of red light, instead of white or green light, might be an appropriate measure to mitigate negative artificial light effects on moth life history.     

Shedding light on moths: shorter wavelengths attract noctuids more than geometrids

With moth declines reported across Europe, and parallel changes in the amount and spectra of street lighting, it is important to understand exactly how artificial lights affect moth populations. We therefore compared the relative attractiveness of shorter wavelength (SW) and longer wavelength (LW) lighting to macromoths. SW light attracted significantly more individuals and species of moth, either when used alone or in competition with LW lighting. We also found striking differences in the relative attractiveness of different wavelengths to different moth groups. SW lighting attracted significantly more Noctuidae than LW, whereas both wavelengths were equally attractive to Geometridae. Understanding the extent to which different groups of moth are attracted to different wavelengths of light will be useful in determining the impact of artificial light on moth populations.     

A role for artificial night-time lighting in long-term changes in populations of 100 widespread macro-moths in UK and Ireland: a citizen-science study

The abundance of 100 of the most widespread species of macro-moth in the UK and Ireland was estimated from light-trap records reported to the UK and Ireland Garden Moth Scheme between 2005 and 2015. Recording sites were classified into low, medium and high night-time illumination categories by satellite imagery, into land-use types from the dominant use in the 1–2 km surrounding area, and by latitude. Most urban sites were in the group classified as having high night-time illumination. Comparison between medium and low night-time illuminated sites allowed differences between levels of illumination free from the effect of urbanization on moth abundance to be assessed. The medium and low night-time illuminated sites differed significantly in the frequency of grassland and arable land-use types and in geographic location with more grassland and north-western sites in the low-light category. After adjustment for these differences and for variations between taxonomic family groups, the medium to low night-time lighting abundance ratios explained a significant (P?<?0.001) 20% of the variance in long-term changes in moth abundance reported by the Rothamsted Insect Survey for the years 1968–2002. This is the first demonstration that artificial night-time lighting has had, in combination with other factors, a significant influence on levels of abundance of moth populations.     

Insect reactions to light and its applications to pest management

Insects are able to see ultraviolet (UV) radiation. Nocturnal insects are often attracted to light sources that emit large amounts of UV radiation, and devices that exploit this behavior, such as light traps for forecasting pest outbreaks, and electric insect killers, have been developed. Some diurnal species are attracted to yellow; yellow pan traps are used for conducting surveys for pest outbreaks and yellow sticky plates are used for pest control. Lamps that give off yellow illumination have been used effectively to control the activity of nocturnal moths and thus reduce damage to fruit, vegetables, and flowers. Covering cultivation facilities with film that filters out near-UV radiation reduces the invasion of pests such as whiteflies and thrips into the facilities, thus reducing damage. Reflective material placed on cultivated land can control the approach of flying insects such as aphids. Future development and use of new light sources such as light-emitting diodes is anticipated for promoting integrated pest management.     

Contrasting effects of habitat quantity and quality on moth communities in fragmented landscapes

Habitat loss is commonly identified as a major threat to the loss of global biodiversity. In this study, we expand on our previous work by addressing the question of how lepidopteran species richness and composition vary among remnants of North American eastern deciduous forest located within agricultural or pastoral landscapes. Specifically, we tested the relative roles of habitat quantity (measured as stand area and percent forest in the greater landscape) and habitat quality (measured as tree species diversity) as determinants of moth species richness. We sampled >19 000 individuals comprising 493 moth species from 21 forest sites in two forested ecoregions. In the unglaciated Western Allegheny Plateau, the species richness of moths with woody host plants diminished as forest stand size and percent forest in the landscape decreased, but the total species richness and abundance of moths were unaffected by stand size, percent forest in the landscape, or tree species diversity. In contrast, the overall species richness and abundance of moths in the glaciated North Central Tillplain were affected primarily by tree species diversity and secondarily by forest size. Higher tree species diversity may reduce species loss from smaller forest stands, suggesting that small, diverse forests can support comparable numbers of species to those in less diverse, large stands. Smaller forests, however, contained a disproportionate number of moth species that possess larvae known to feed on herbaceous vegetation. Thus, although woody plant feeding moths are lost from forests with changes in stand area, new species appear capable of recolonizing smaller fragments from the surrounding habitat matrix. Our study further suggests that when species replacement occurs, local patch size and habitat quality may be more important than landscape context in determining the community structure of forest Lepidoptera.     

Artificial night lighting disrupts sex pheromone in a noctuid moth

1. One major, yet poorly studied, change in the environment is the increase in nocturnal light pollution. Although this strongly alters the habitat of nocturnal species, the ecological consequences are poorly known. Moths are well known to be attracted to artificial light sources, but artificial light may affect them in other ways as well. 2. In this study, female Mamestra brassicae moths were subjected to various types of low‐intensity artificial night lighting with contrasting spectral compositions (green‐rich, red‐rich, warm white) or to a dark control treatment and the effects on their sex pheromone production and composition were tested. 3. Artificial night lighting reduced sex pheromone production and altered the chemical composition of the pheromone blend, irrespective of spectral composition. Specifically, amounts of the main pheromone component Z11‐16:Ac were reduced, while the deterring compounds Z9‐14:Ac, Z9‐16:Ac, and Z11‐16:OH were increased relative to Z11‐16:Ac when females were kept under artificial light. These changes may reduce the effectiveness of the sex pheromones, becoming less attractive for males. 4. These results show for the first time that artificial light at night affects processes that are involved in moth reproduction. The potential for mitigation through manipulation of the spectral composition of artificial light appears limited.     

The dark side of street lighting: impacts on moths and evidence for the disruption of nocturnal pollen transport

Among drivers of environmental change, artificial light at night is relatively poorly understood, yet is increasing on a global scale. The community‐level effects of existing street lights on moths and their biotic interactions have not previously been studied. Using a combination of sampling methods at matched‐pairs of lit and unlit sites, we found significant effects of street lighting: moth abundance at ground level was halved at lit sites, species richness was >25% lower, and flight activity at the level of the light was 70% greater. Furthermore, we found that 23% of moths carried pollen of at least 28 plant species and that there was a consequent overall reduction in pollen transport at lit sites. These findings support the disruptive impact of lights on moth activity, which is one proposed mechanism driving moth declines, and suggest that street lighting potentially impacts upon pollination by nocturnal invertebrates. We highlight the importance of considering both direct and cascading impacts of artificial light.     

High duty cycle pulses suppress orientation flights of crambid moths

Bat-and-moth is a good model system for understanding predator–prey interactions resulting from interspecific coevolution. Night-flying insects have been under predation pressure from echolocating bats for 65 Myr, pressuring vulnerable moths to evolve ultrasound detection and evasive maneuvers as counter tactics. Past studies of defensive behaviors against attacking bats have been biased toward noctuoid moth responses to short duration pulses of low-duty-cycle (LDC) bat calls. Depending on the region, however, moths have been exposed to predation pressure from high-duty-cycle (HDC) bats as well. Here, we reveal that long duration pulse of the sympatric HDC bat (e.g., greater horseshoe bat) is easily detected by the auditory nerve of Japanese crambid moths (yellow peach moth and Asian corn borer) and suppress both mate-finding flights of virgin males and host-finding flights of mated females. The hearing sensitivities for the duration of pulse stimuli significantly dropped non-linearly in both the two moth species as the pulse duration shortened. These hearing properties support the energy integrator model; however, the threshold reduction per doubling the duration has slightly larger than those of other moth species hitherto reported. And also, Asian corn borer showed a lower auditory sensitivity and a lower flight suppression to short duration pulse than yellow peach moth did. Therefore, flight disruption of moth might be more frequently achieved by the pulse structure of HDC calls. The combination of long pulses and inter-pulse intervals, which moths can readily continue detecting, will be useful for repelling moth pests.     

Declines in moth populations stress the need for conserving dark nights

Given the global continuous rise, artificial light at night is often considered a driving force behind moth population declines. Although negative effects on individuals have been shown, there is no evidence for effects on population sizes to date. Therefore, we compared population trends of Dutch macromoth fauna over the period 1985–2015 between moth species that differ in phototaxis and adult circadian rhythm. We found that moth species that show positive phototaxis or are nocturnally active have stronger negative population trends than species that are not attracted to light or are diurnal species. Our results indicate that artificial light at night is an important factor in explaining declines in moth populations in regions with high artificial night sky brightness. Our study supports efforts to reduce the impacts of artificial light at night by promoting lamps that do not attract insects and reduce overall levels of illumination in rural areas to reverse declines of moth populations.     

Moth sex pheromone adsorption to leaf surface: bridge in time for chemical spies

Abstract When brussels sprouts leaves were exposed to air passed over a single calling Mamestra brassicae moth, sex pheromone was adsorbed onto the leaf surface to such an extent that it subsequently elicited behavioural responses in conspecific male moths, as well as in female Trichogramma evanescens , egg parasitoids of M. brassicae. Male moths responded to odour-treated leaves over a short distance (c. 5 cm) in a wind tunnel, but were not attracted at a distance of 1 m. In contrast, sex pheromone adsorbed to and re-released from the glass wall of a wind tunnel compartment attracted male moths from 1 m. Trichogramma's locomotory behaviour on leaves is described. On leaves previously exposed to air passed over a calling female moth, Trichogramma wasps stayed significantly longer on leaves treated with clean air or air passed over a non-calling female moth. In addition, wasps spent relatively more time along the margin and on the leaf underside on treated leaves compared with control leaves. All effects persisted for at least 4 h, and after 24 h treated leaves still increased wasp residence times. These results are the first example of responses of male moths to adsorbed airborne sex pheromone originating from a single female moth. They further suggest how sex pheromone released by nocturnal moths may function as a kairomone for diurnally foraging parasitoids.     

Nursery pollination by a moth in Silene latifolia: the role of odours in eliciting antennal and behavioural responses

Since the 1970s it has been known that the nursery pollinator Hadena bicruris is attracted to the flowers of its most important host plant, Silene latifolia, by their scent. Here we identified important compounds for attraction of this noctuid moth. Gas chromatographic and electroantennographic methods were used to detect compounds eliciting signals in the antennae of the moth. Electrophysiologically active compounds were tested in wind-tunnel bioassays to foraging na?ve moths, and the attractivity of these compounds was compared with that to the natural scent of whole S. latifolia flowers. The antennae of moths detected substances of several classes. Phenylacetaldehyde elicited the strongest signals in the antennae, but lilac aldehydes were the most attractive compounds in wind-tunnel bioassays and attracted 90% of the moths tested, as did the scent of single flowers. Our results show that the most common and abundant floral scent compounds in S. latifolia, lilac aldehydes, attracted most of the moths tested, indicating a specific adaptation of H. bicruris to its host plant.     

Preliminary observations on the response of Chironex fleckeri (Cnidaria: Cubozoa: Chirodropida) to different colors of light

Cubozoans are well known for their attraction to light and light-colored objects. Two highly venomous types are a public safety concern in Australian waters and elsewhere: Chironex fleckeri, long considered the world's deadliest animal and colloquially called the box jellyfish; and the irukandjis, a group of at least 10 species that cause various degrees of debilitating illness. We were asked by the tourism industry whether there might be a color of light that box jellyfish and irukandjis are not attracted to, such that nighttime diving activities might pose less risk of being stung. Our preliminary trials with Chironex fleckeri indicated a marked positive response to lights of white, red, yellow, green, orange, and blue. All colors elicited a strong and directed attraction to light; however, medusae slowed down their pulsation rate, streamed out their tentacles, and performed a series of figure-eight patterns back and forth through the lighted area when exposed to blue light, which we interpreted as feeding behavior. This compares curiously with a report subsequent to our testing, in which the small, mangrove-inhabiting cubomedusa Tripedalia cystophora and the beach-dwelling Chiropsella bronzie demonstrate a peak sensitivity to blue-green light in the region of 500 nm, and that the former is behaviorally attracted to blue and green light, but ignores red. This leaves open the possibility that Irukandji species, which are more closely related to Tripedalia than to Chironex, may be blind to red.     

Compatibility of codling moths Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) from South Africa with codling moths shipped from Canada

The sterile insect technique (SIT) has been successfully applied against codling moth Cydia pomonella (Linnaeus) (Lepidoptera; Tortricidae) in British Columbia since 1992 where the mass‐rearing facility produces between 15 and 16 million moths per week. Due to the seasonality of this pest, the facility is only fully utilized for part of the year. The time and expense of implementing SIT against codling moth in South Africa may be substantially reduced if moths from Canada were sexually compatible with those from South Africa. In addition, because the pome fruit‐growing season in both countries is opposite, the programme in Canada might benefit by maintaining moth production year‐round and selling moths to South Africa. Semi‐field studies in small cages and release‐recapture studies were conducted in an unsprayed apple orchard in South Africa to assess mating compatibility of laboratory‐reared codling moth from Canada and wild codling moths from South Africa. The results suggest that Canadian codling moth males were equally attracted to calling Canadian and South African females despite the fact that Canadian moths had been transported (from Canada to South Africa) for 48 h as both pupae and adults. The data also suggest that at lower field temperatures Canadian moths were more active than South African moths. Results from the release‐recapture field trials indicated that Canadian and South African males were equally attracted to Canadian and South African females. These results suggest that codling moths from Canada and South Africa are fully compatible and indicate that Canadian moths can be used for SIT studies in South Africa. As these studies were conducted with moths from two very different climatic and time zones, it is proposed that populations of codling moth in other pome fruit production areas may also be compatible with the Canadian moths.     

Response of female oriental fruit moth to volatiles from apple and peach trees at three phenological stages

The attractiveness of peach ( Prunus persica L. Batsch) and apple ( Malus domestica L. Borkh.) (both Rosaceae) tissue to gravid female oriental fruit moth, Grapholita (=  Cydia ) molesta (Busck) (Lepidoptera: Tortricidae), was assessed at three distinct stages throughout the growing season using a dual-choice bioassay. Plant material offered to the female moths consisted of a plant shoot in early spring, before fruit became available. Later, it consisted of a leaf-bearing twig and a fruit, either alone or in combination. The level of attraction of the female moths to the various plant tissues varied substantially over time and according to the plant species. Before fruit became available, female moths were significantly attracted to peach as well as to apple shoots. During the early fruit growth stage, moths were attracted to a leaf-bearing twig originating from a peach tree, but not to that from an apple tree. In peach, it was the vegetative tissue that accounted for the attraction, whereas in apple, it was the reproductive tissue (a developing fruit). During the late fruit growth stage, both peach fruit and apple fruit were highly attractive, whereas a twig with leaves from either an apple or a peach tree was neither attractive nor repellent to the female moths. This changing female olfactory response to volatiles emitted by vegetative tissue and fruits from the two host plant species with progressing season is discussed with respect to the biology and the dispersal of this moth species.     

Moths pollinate four crops of Cucurbitaceae in Asia

Pollination ecology of many crops is not fully known, especially in tropical and subtropical regions. Non-bee pollinators may contribute substantially to crop yield, even if they do not receive much attention. Although moth pollination has fascinated ecologists and evolutionary biologists since Darwin, crop pollination by moths has not been well investigated and experimentally examined. Hence, we explored the pollination ecology of four cucurbit crops with crepuscular or nocturnal flowers. Lagenaria siceraria (Molina) Standl., Luffa acutangula (L.) Roxb., Trichosanthes anguina L., and Trichosanthes kirilowii Maxim. all display floral traits suggestive of moth pollination, such as opening around dusk or in evenings and secreting ample dilute nectar. We demonstrated that these crops’ flowers attracted a wide range of moth species, especially hawkmoths. The assemblage of flower-visiting moths varied according to location and season. Pollination treatments and pollen load analysis confirmed the pollination of the four crops by moths, especially hawkmoths. Our results provide evidence for the value as wild pollinators for the four crops, for which domesticated bees cannot provide reliable pollination services in practice. This study lends support to the proposal to pay more attention to the value of non-bee pollinators and to leave some areas unexploited in rural landscapes for the conservation of wild pollinators, including moths.     

Expansion of the winter moth outbreak range: no restrictive effects of competition with the resident autumnal moth

1. Both direct and indirect competition can have profound effects on species abundance and expansion rates, especially for a species trying to strengthen a foothold in new areas, such as the winter moth (Operophtera brumata) currently in northernmost Finland. There, winter moths have overlapping outbreak ranges with autumnal moths (Epirrita autumnata), who also share the same host, the mountain birch (Betula pubescens ssp. czerepanovii). Competitive interactions are also possible, but so far unstudied, are explanations for the observed 1–3 years phase lag between the population cycles of the two moth species. 2. In two field experiments, we studied host plant‐mediated indirect inter‐specific competition and direct interference/exploitation competition between autumnal and winter moths. The experimental larvae were grown either with the competing species or with the same number of conspecifics until pupation. Inter‐specific competition was judged from differences in pupal mass (reflecting lifespan fecundity), larval development time and larval survival. 3. Larval performance measurements suggested that neither direct nor indirect inter‐specific competition with the autumnal moth reduce the growth rate of winter moth populations. Winter moths even had a higher probability of survival when reared together with autumnal moths. 4. Thus, we conclude that neither direct nor indirect inter‐specific competition is capable of suppressing the spread of the winter moth outbreak range and that both are also an unlikely cause for the phase lag between the phase‐locked population cycles of the two moth species.     

Leaf variegation in Caladium steudneriifolium (Araceae): a case of mimicry?

The leaves of Caladium steudneriifolium (Araceae) of the understorey of a submontane rainforest in the Podocarpus National Park (South East Ecuador, 1,060 m a.s.l.) are plain green or patterned with whitish variegation. Of the 3,413 individual leaves randomly chosen and examined in April 2003, two-thirds were plain green, whereas one third were variegated (i.e., whitish due to absence of chloroplasts). Leaves of both morphs are frequently attacked by mining moth caterpillars. Our BLAST analysis based on Cytochrome-c-Oxidase-subunit-1 sequences suggests that the moth is possibly a member of the Pyraloidea or another microlepidopteran group. It was observed that the variegated leaf zones strongly resemble recent damages caused by mining larvae and therefore may mimic an attack by moth larvae. Infestation was significantly 4–12 times higher for green leaves than for variegated leaves. To test the hypothesis that variegation can be interpreted as mimicry to deter ovipositing moths, we first ruled out the possibility that variegation is a function of canopy density (i.e., that the moths might be attracted or deterred by factors unrelated to the plant). Then plain green leaves were artificially variegated and the number of mining larvae counted after 3 months. The results on infestation rate (7.88% of green leaves, 1.61% of the variegated leaves, 0.41% of white manipulated leaves and 9.12% of uncoloured manipulated leaves) suggest that ovipositing moths are deterred by the miner-infestation mimicry. Thus, variegation might be beneficial for the plants despite the implicated loss of photosynthetically active surface.     

Conservation of moths in The Netherlands: population trends, distribution patterns and monitoring techniques of day-flying moths

The loss of butterfly diversity in north-western Europe has been studied extensively but much less is known about the status of other macrolepidoptera. The present paper presents results of the research on mainly day-flying larger moths carried out by Dutch Butterfly Conservation in The Netherlands. Research started in 1992 with a public campaign and a mapping programme, leading to an increase in the number of records of macrolepidoptera. Results from the mapping programme on day-flying moths showed a strong general decrease in The Netherlands, comparable with the loss of butterfly diversity. Transect counts have been undertaken since 2000 for a few species and this method is sufficient to measure trends over time if the moth densities are high enough. Another research component was to focus on marshland habitats in The Netherlands. Fifty-five characteristic marshland moth species were selected and the relative abundance of nearly all these species has declined. These trends were compared with four other countries in the Atlantic biogeographical zone. The relative abundance of the majority of marshland moths in The Netherlands was found to be higher than those in other European countries, so that The Netherlands has a special responsibility for the conservation of the moths of its marshes. Moreover, we emphasise that, next to butterflies, moths can be of great use in nature conservation because of their potential significance as indicator species in endangered habitats.     

Detection of Prey by a Spider that Aggressively Mimics Pheromone Blends

Adult female bolas spiders have a unique hunting tactic that combines aggressive chemical mimicry of the sex pheromone blends of their prey moths with a specialized weapon (the bolas) and behaviors to capture attracted male moths. This report shows that female bolas spiders can release the attractive allomone before they make the bolas and that females detect moth wing vibrations from attracted prey. In response to this detection, females initiate the construction of a bolas. This ability to sample for prey presence may allow this predator to adapt its hunting activity to the temporal and spatial availability of its prey and, thereby, may reduce the constraints associated with extreme prey specialization.