Foraging and mate-finding in the silver Y moth, Autographa gamma (Lepidoptera: Noctuidae) under the risk of predation

Animal foraging and reproductive behaviour is influenced by other simultaneous demands such as predator avoidance. The trade-offs between these demands may depend on sex or mating experience. This study demonstrates that the olfactory-mediated foraging and mate-seeking behaviours in the silver Y moths, Autographa gamma , are affected by auditory cues mimicking their bat predators. Both males and females changed their foraging behaviour under simulated predation risk. Fewer moths reached the odour source following sound stimulation and the time to find the odour source increased by up to 250%. However, there were no significant differences between male and female ability to reach the plant odour source or the duration of the flight towards the source when stimulated with ultrasound. Hence females are not more cautious than males when observed in the same behavioural context. Risk-taking in males was independent of whether they were flying toward a flower odour or sex pheromones having equal attractive value. This indicates that the trade-off between olfactory and acoustic cues is independent the type of odour. Mated females were not as strongly affected by sound as non-mated, indicating that flower odours have a higher adaptive value for mated females, suggesting that some processes following mating experience influence the trade-off between flower odours and simulated bat sounds.     

Odour-mediated nectar foraging in the silver Y moth, Autographa gamma (Lepidoptera: Noctuidae): behavioural and electrophysiological responses to floral volatiles

Naive male and female silver Y moths, Autographa gamma (Lepidoptera: Noctuidae), were attracted in a flight tunnel assay to potted creeping thistle, Cirsium arvense (Asteraceae), butterfly-orchid, Platanthera bifolia (Orchidaceae), soapwort, Saponaria officinalis (Caryophyllaceae), greater knapweed, Centaurea scabiosa (Asteraceae), red clover, Trifolium pratense (Fabaceae), and catnip, Nepeta faasseni (Labiatae), plants with flowers. The most attractive plants were C. arvense , P. bifolia and S. officinalis that elicited 87, 78 and 65% source contacts, respectively. C. scabiosa was less attractive eliciting 43% response. T. pratense and N. faasseni showed the least attraction eliciting 28 and 26% source contacts, respectively. A cotton plant used as control, was not attractive. Floral volatiles from the investigated plant species were collected using headspace sampling technique. Samples were analysed using gas chromatography coupled with electroantennographic detection, and electrophysiologically active compounds were identified by coupled gas chromatography/mass spectrometry. Consistent electrophysiological responses were elicited by twelve compounds from headspace of C. arvense , thirteen compounds from P. bifolia , eleven compounds from S. officinalis , nine from C. scabiosa , ten from T. pratense and two from N. faasseni . Most of the active compounds were specific for one or two species, while benzyl benzoate was present in four and benzaldehyde and benzyl alcohol in three species. Floral scents of C. arvense , P. bifolia and S. officinalis , the most attractive flowers, were dominated by aromatic compounds that were not abundant in the scent of other flowers. To conclude, the results demonstrate the absence of a common denominator of odours present in flowers of different plants visited by A. gamma .     

Allocation to reproduction following experimental defoliation in Platanthera bifolia (Orchidaceae)

The roles of herbivory and pollination success in plant reproduction have frequently been examined, but interactions between these two factors have gained much less attention. In three field experiments, we examined whether artificial defoliation affects allocation to attractiveness to pollinators, pollen production, female reproductive success and subsequent growth in Platanthera bifolia L. (Rich.). We also recorded the effects of inflorescence size on these variables. We studied the effects of defoliation on reproductive success of individual flowers in three sections of inflorescence. Defoliation and inflorescence size did not have any negative effects on the proportion of opened flowers, spur length, nectar production or the weight of pollinia. However, we found that hand-pollination increased relative seed production and defoliation decreased seed set in most cases. Interactions between hand-pollination and defoliation were non-significant indicating that defoliation did not affect female reproductive success indirectly via decreased pollinator attraction. Plants with a large inflorescence produced relatively more seeds than plants with a small inflorescence only after hand-pollination. The negative effect of defoliation on relative capsule production was most clearly seen in the upper sections of the inflorescence. In addition to within season effects of leaf removal, defoliated P. bifolia plants may also have decreased lifetime fitness as a result of lower seed set within a season and because of a lower number of reproductive events due to decreased plant size (leaf area) following defoliation. Our study thus shows that defoliation by herbivores may crucially affect reproductive success of P. bifolia.     

Variable selection in Platanthera bifolia (Orchidaceae): phenotypic selection differed between sex functions in a drought year

We estimated selection on three morphological characters in the hermaphroditic, hawkmoth-pollinated orchid Platanthera bifolia and explored selection surfaces through male and female function. The work was carried out in northern Sweden during two flowering seasons (1994 and 1995) in one natural population and one season (1995) in another natural population. Fitness was estimated as number of pollinia removed (male function) and number of fruits produced (female function). We detected directional selection towards larger inflorescence size (flower number) through both sex functions in both populations in 1995. In 1994, with an unusually dry growing season, 78% of the individuals failed to set any fruit, and there was selection for larger inflorescences only through male function. In this year, there was selection towards longer flower spurs, which could be a direct or indirect effect of spurs being shortened by drought. The results demonstrate that selection patterns may vary temporally and spatially, and that the 'male function hypothesis' may be applicable as female function is more resource dependent than male function.     

Patterns of Genetic Diversity in Platanthera bifolia (Orchidaceae) with Respect to Life History Traits and Recent Range Expansion

For evolutionary and ecological analyses, genetic diversity at different scales needs to be studied in terms of biological properties, habitat, population size and population history. We surveyed Platanthera bifolia populations from six regions in northeastern Poland to determine the impact of the mating system and population history on genetic diversity. Based on variation at allozyme markers, genetic variation was relatively moderate (P?=?22.3%, A?=?1.48, H _O?=?0.083, F _IS?=??0.015) and similar to other Platanthera species. These parameters varied between populations (P?=?13.3%–26.6%, A?=?1.26–1.66, H _O?=?0.055–0.111, F _IS?=??0.262–0.147). The genetic diversity patterns were shaped by different proportions of facilitated selfing and/or outcrossing, resulting in positive and negative F _IS values, respectively. No relationship between inbreeding coefficient and population size, however, and no impact of apomixis on the level of genetic diversity of P. bifolia were found. The relatively low level of genetic differentiation among the investigated regions (F _CT?=?0.002, P?>?0.05) and among populations (F _ST?=?0.048, P?<?0.001), and the lack of a significant relationship between genetic and geographical distance, are discussed in the context of possible scenaria of postglacial expansion.     

Characteristics and distribution of intermediates between Platanthera bifolia and P. chlorantha (Orchidaceae) in the Nordic countries

In areas of sympatry Plantanthera bifolia (L.) L. C. Rich. and P. chlorantha (Cust.) Rchb. occasionally produce hybrids. These plants exhibit intermediate floral morphology. The present study presents the distribution, floral morphology, and general characteristics of these intermediates in the Nordic area. The most useful and reliable diagnostic characters for hybrid plants were (1) the distance between viscidia (normally about 1.4 mm), (2) the length of the caudicle of pollinia (about 0.7 mm), and (3) the presence of a distinct pedicel at the connection between caudicle and viscidium. Comparative chemical analyses of the floral fragrances are reported. Material in the principal Nordic herbaria indicated a generally low production of hybrids (0.46%) and that the main area of occurrence is SE Sweden and Alandia, Finland. Intermediates seem more frequent in provinces where P. bifolia is relatively long-spurred. Very few were recorded from Denmark and Norway (hybrids in the latter country here reported for the first time). Aggregations of intermediates displaying patterns of introgressive hybridization were found only on Öland and Gotland. Occurrence of hybrids outside the Nordic area is also discussed and remarks are made on the morphologically similar P. metabifolia Maek. in E Asia. All known Nordic intermediates are listed.     

Susceptibility of potato tuber moth (Lepidoptera: Gelechiidae) to postharvest gamma irradiation

Gamma irradiation doses applied to inhibit potato sprouting were tested against potato tuber moth larval and pupal stages. Young larvae and pupae were more susceptible to irradiation injuries than older ones. When larvae of different ages were exposed to doses > or = 100 Gy, only 13-35% pupated, but no adult emergence was obtained. The exposure of 1-1.5- or 3-3.5-d-old pupae to 150 Gy induced high level of sterility and remarkable reduction in female mating ability and fecundity, whereas the reduction was less noticeable for 5-5.5-d-old pupae. Postharvest gamma irradiation of potatoes could be considered as an efficient control approach against potato tuber moth larval and pupal infestations.     

Chemoreceptors in the cibario-pharyngeal pump of the cabbage looper moth,Trichoplusia ni (Lepidoptera: Noctuidae)

The structure of contact chemoreceptors in the cibariopharyngeal pump of the moth Trichoplusia ni (Lepidoptera: Noctuidae) is described. Two types of receptors designated A and B are located on the floor of the pump. Two groups of 9-12 A receptors are located in the anterior part of the pump, and two groups of two B receptors are in the posterior part of the pump. Five sensory dendrites extend to the tip of each A receptor and four to each B receptors. Available evidence indicates that these receptors are contact chemoreceptors and do not serve as mechanoreceptors. The receptors are compared to those of other insects.     

Comparative susceptibilities of diamondback moth (Lepidoptera: Plutellidae) and cabbage looper (Lepidoptera: Noctuidae) from Minnesota and south Texas to lambda-cyhalothrin and indoxacarb

The susceptibility of early instars of diamondback moth, Plutella xylostella (L.), and early (first and second) and late instars (third and fourth) of cabbage looper, Trichoplusia ni (Hübner), from Minnesota and south Texas, to indoxacarb and lambda-cyhalothrin was determined in the laboratory. Susceptibilities of the two species from the two geographical locations to indoxacarb and lambda-cyhalothrin varied greatly. P. xylostella from Minnesota was as susceptible to indoxacarb as those from south Texas, whereas both early and late instar T. ni from south Texas were significantly more tolerant to indoxacarb than those from Minnesota. The LC50 values of indoxacarb for early and later instar T. ni at 48 h from south Texas were 4.3- and 34.0-fold greater than those from Minnesota, respectively. Similarly, early instar P. xylostella and late instar T. ni from south Texas were significantly less susceptible to lambda-cyhalothrin than those from Minnesota. Percentage mortality of the two insect species caused by the two insecticides varied with time of exposure and generally exhibited similar patterns of responses to different concentrations for each insecticide.     

Aestival dormancy in the cabbage moth Mamestra brassicae L. (Lepidoptera: Noctuidae)

Summary A highly specific recognition system, capable of foreseeing and distinguishing between two critical points in time, exists in Mamestra brassicae (Lepidoptera: Noctuidae). Both points in time, the onset of a drought period and the end of the growth season, require different growth patterns of the pupae. In order to minimize the likelihood of weather-induced mortality and to maximize fitness, individuals of M. brassicae must enter aestival dormancy or hibernal diapause, respectively, before the onset of drought or frost. This study is primarily concerned with aestival dormancy. Normally, the pupal period of dormancy-free developing individuals amounts to approximately 20 to 30 days. A modified pupal period of approximately 35 to 80 days is defined as aestival dormancy. The onset of aestival dormancy is triggered by day lengths exceeding an innate individaul-specific threshold. The results reported in this paper indicate that the photoperiodic response curve represents largely the genetic variability within a population with respect to the thresholds triggering aestival dormancy. This variability in thresholds is considered to reflect the frequency of correlation of a distinct day length with a certain onset of drought period in the past. Furthermore, the innate thresholds are characterized by a temperature dependent norm of reaction. Our results also indicate, that a strong genetical component is involved in variability of duration of the pupal period. This variability in duration of aestivation reflects the frequency of drought periods of a certain length in the past. The adaptive significance of both the variation in day length thresholds and duration of aestival dormancy is discussed with respect to the number of generations per season, and the synchronization of the individual life cycles with the seasonal changing environmental conditions.This study is dedicated to Prof. H.J. Müller, Jena, for his 75th anniversaryThis research was supported by the Deutsche Forschungsgemeinschaft (Sa 259/3-1)     

Processes of isolation and introgressive interplay between Platanthera bifolia (L.) Rich and P. chlorantha (Custer) Reichb. (Orchidaceae)

NILSSON, L. A., 1983. Processes of isolation and introgressive interplay between Platanthera bifolia L. Rich, and P. chlorantha (Custer; Reichb. (Orchidaceae). Platanthera bifolia and P. chlorantha are highly specialized for pollination by crepuscular and nocturnal Lepidoptera. The plants are largely sympatric, have overlapping flowering-times, and are completely interfertile. Principal differences exist in floral fragrance and column morphology. Isolation is effected by a set of integrated morphological, ethological, and seasonal mechanisms. Odour-based constancy by moths, differences in column structure, attachment of pollinaria, spurlength, nectar availability, and flowering-peaks reduce interspecific pollen transfer. The plants form a functional species pair in relation to their pollination environment and locally share the same main pollinator species.
Hybrids, which infrequently occur in areas of sympatry, emit a blend of the species-specific fragrance compounds and have intermediate column structure. They are frequently visited by-moths but suffer a serious reduction in seed production due to imperfect interaction vis-à-vis the pollen vectors. Hybrid viscidia, in an intermediate position on the column, are touched by moths' scaly and hairy palps and get insufficient attachment, evidently causing hybrids to act solely as female recipient. First backcross individuals largely join the functional range of either species which promotes rapid introgression. The two gene-pools interplay, although always at a low level. Patterns of introgressive hybridization were exemplified.     

Aestival dormancy in the cabbage moth Mamestra brassicae L. (Lepidoptera: Noctuidae)

Summary In a geographically wide distribution the life cycles of different populations of the cabbage moth Mamestra brossicae are adapted to a remarkable diversity of climatic conditions. This is undoubtedly a proof of its success in adaptation. Some populations living in regions characterized by a drought period interrupting the growth season are capable of distinguishing between one critical day length signalling the onset of the drought period and another signalling the end of the growth season. This study, therefore, is primarily concerned with the geographical patterns in the variability of the adaptional responses of populations exposed to environmental conditions requiring different strategies and tactics in, synchronizing individual, life cycles. It is also a contribution to our understanding of evolutionary mechanisms maintaining median responses to photoperiodically inductive day lengths in geographically different populations. The populations investigated originated from regions differing in predictability of the incidence, onset and duration of a drought period: Freiburg (48.0°N, Southern Germany), Avignon (44.0°N, Southern France), and Argelès (42.5°N, Southern France). Geographical variation with respect to both onset and duration of a drought period consequently results in clinal variation of the variability of innate day length thresholds triggering aestival dormancy and of innate duration of aestivation. In this paper we considered the influence of geographically changing temperatures on aestival dormancy induction. Even in southern populations of M. brassicae a temperature dependent switch off-mechanism exists which prevents aestival dormancy under certain environmental conditions. The effective temperatures vary geographically, too. What the geographical patterns in adaptive responses really are, is discussed.This research was supported by the Deutsche Forschungsgemeinschaft (Sa 259/3-1)     

Genetic differentiation in Scottish populations of the pine beauty moth, Panolis flammea (Lepidoptera: Noctuidae)

Pine beauty moth, Panolis flammea (Denis & Schiffermüller), is a recent but persistent pest of lodgepole pine plantations in Scotland, but exists naturally at low levels within remnants and plantations of Scots pine. To test whether separate host races occur in lodgepole and Scots pine stands and to examine colonization dynamics, allozyme, randomly amplified polymorphic DNA (RAPD) and mitochondrial variation were screened within a range of Scottish samples. RAPD analysis indicated limited long distance dispersal (FST=0.099), and significant isolation by distance (P<0.05); but that colonization between more proximate populations was often variable, from extensive to limited exchange. When compared with material from Germany, Scottish samples were found to be more diverse and significantly differentiated for all markers. For mtDNA, two highly divergent groups of haplotypes were evident, one group contained both German and Scottish samples and the other was predominantly Scottish. No genetic differentiation was evident between P. flammea populations sampled from different hosts, and no diversity bottleneck was observed in the lodgepole group. Indeed, lodgepole stands appear to have been colonized on multiple occasions from Scots pine sources and neighbouring populations on different hosts are close to panmixia.     

Phenotypic plasticity and geographical variation in the pre-reproductive period of Autographa gamma (Lepidoptera: Noctuidae) and its implications for migration in this species

Abstract.

• 1 Adults of the noctuid moth Autographa gamma undertake seasonal migrations into areas where they are unable to breed continuously. Individuals migrate into Britain each spring, and offspring of these migrants probably return in autumn to over-wintering areas in North Africa and the Middle East. However, the existence of these return migrations has been questioned.
• 2 Insects usually migrate during the adults' pre-reproductive period (PRP). The length of this period is therefore an index of migratory potential since individuals with longer PRPs have more time to express their potential for flight and to travel further before becoming sexually mature.
• 3 Offspring of insects from Morocco, Britain and Germany showed that, under both long and short photoperiods, PRP increased with latitude over the range 34–53°N. There were significant genotype—environment interactions in the effect of photoperiod on length of PRP.
• 4 However, PRPs of offspring from insects collected in Sweden were no different under a long photoperiod from those of offspring collected further south, and were significantly shorter under a short photoperiod than those of insects from Morocco.
• 5 With the exception of Swedish moths, offspring from insects collected at higher latitudes had longer PRPs and, therefore, the potential to travel further during migrations. The ability of some individuals to respond to environmental cues signalling habitat deterioration will further increase their potential to return to over-wintering areas further south.

     

Palatability and defense in the aposematic diurnal whistling moth, Hecatesia exultans Walker (Lepidoptera: Noctuidae: Agaristinae)

Abstract Aposematic colours may warn predators that an individual or species is chemically defended and unpalatable. This study examines a diurnal Australian whistling moth, Hecatesia exultans (Noctuidae, Agaristinae) where adults, although cryptic at rest, display their bright orange, yellow and black colouration in flight. Aposematically coloured larvae feed mainly on Cassytha, a parasitic vine that contains aporphine alkaloids. Alkaloids isolated from the plants and moths were analysed for the presence of these compounds. While alkaloids were found in the stomach and frass of 18 moth larvae, no alkaloids were present in the body and similarly no alkaloids were detected from 65 adult male moths collected from three widely separated populations. We conclude that the larvae and adults do not sequester alkaloids. Lycosid spiders and singing honeyeaters ( Lichenostomtus virescens ) were used to assess the palatability of H. exultans adults. The spiders and the birds consumed all adult moths. Adult moths appear to avoid predation by employing quick flights with rapid changes of direction and, while the adults are brightly coloured, they are not chemical defended.     

Spatial representation of odours in the antennal lobe of the moth Spodoptera littoralis (Lepidoptera: Noctuidae)

Glomeruli within the antennal lobe (AL) of moths are convergence sites for a large number of olfactory receptor neurons (ORNs). The ORNs target single glomeruli. In the male-specific cluster of glomeruli, the macroglomerular complex (MGC), the input is chemotypic in that each glomerulus of the MGC receives information about a specific component of the conspecific female sex pheromone. Little is known about how neurons that detect other odorants arborize in and amongst glomeruli. The present study focuses on how sex pheromones and biologically relevant semiochemicals are represented in the ALs of both sexes of the moth Spodoptera littoralis. To assess this, we optically measured odour-evoked changes of calcium concentration in the ALs. Foci of calcium increase corresponded in size and shape with anatomical glomeruli. More than one glomerulus was normally activated by a specific non-pheromonal odorant and the same glomerulus was activated by several odorants. All odorants and pheromone components tested evoked unique patterns of glomerular activity that were highly reproducible at repeated stimulations within an individual. Odour-evoked patterns were similar between individuals for a given odorant, implicating a spatial olfactory code. In addition, we demonstrated that activity patterns evoked by host-plant related volatiles are similar between males and females.     

Rapid antibody-based field test to distinguish between Helicoverpa armigera (Lepidoptera: Noctuidae) and Helicoverpa punctigera (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) are the two most important insect pests of cotton production in Australia and require application of insecticides to control them. H. armigera has developed resistance to several insecticides but H. punctigera has not. Cost-effective management of insecticide resistance requires that growers be able to determine the proportion of H. armigera eggs or young larvae present on their crop before applying insecticides. This is impossible visually. We generated two monoclonal antibodies that reacted with the insect protein "lipophorin" and were capable of discriminating individuals of the two species at all life-stages. The antibodies were incorporated into a rapid test kit that was tested under field conditions over two growing seasons. Results obtained with the kit agreed closely with those obtained by rearing larvae through to second instar.     

Structure and function of antennal lobe neurons in the male turnip moth,Agrotis segetum (Lepidoptera: Noctuidae)

Interneurons with dendritic branches in the antennal lobe of the male turnip moth, Agrotis segetum (Schiff., Lepidoptera: Noctuidae), were investigated with intracellular recording and staining methods. Seventeen projection neurons that transmit information from the antennal lobe to higher centers in the brain displayed dendritic arbors in the male specific macroglomerular complex (MGC) and responded to chemical components of the female sex pheromone used in species-specific sexual communication. Most of the projection neurons responded to several of the pheromone components tested, and a precise correlation between the location of the dendritic arborization and the physiological response could not be demonstrated. One MGC-projection neuron fit the definition of blend specialist. It did not respond to the individual components of the behaviorally active pheromone blend, but showed a strong response to the components when combined in the species-specific blend. Some of the projection neurons also showed clear responses to phenylacetaldehyde, a flower-produced compound and/or to (E)-2-hexenal, a common green-leaf volatile. In eight neurons, the axonal projection could be followed to the calyces of the mushroom body, and subsequently to the inferior lateral protocerebrum.Four local interneurons were characterized both morphologically and physiologically. Each neuron arborized extensively throughout the antennal lobe, and each responded to one or several of the pheromone compounds, and/or to one or both of the plant-produced compounds. One of the local interneurons responded exclusively to the pheromone blend, but not to the individual components.Abbreviations AL antennal lobe - AN antennal nerve - CB cell body - E2H (E)-2-hexenal - IACT inner antennocerebral tract - ILPR inferior lateral protocerebrum - LH lateral horn of the protocerebrum - LN local interneuron - MB mushroom body - MGC macroglomerular complex - OACT outer antennocerebral tract - PAA phenylacetaldehyde - PN projection interneuron - RN receptor neuron - Z5-10:OAc (Z)-5-decenyl acetate - Z5-10:OH (Z)-5-decenol - Z5-12:OAc (Z)-5-dodecenyl acetate - Z7-12:OAc (Z)-7-dodecenyl acetate - Z9-14:OAc (Z)-9-tetradecenyl acetate     

A flagellate protozoan from Mythimna separata (Lepidoptera: Noctuidae)

Abstract

A trypanosomatid flagellate, Herpetomonas sp., is recorded from an adult Mythimna separata (Walker) (Lepidoptera: Noctuidae). Promastigote, paramastigote, and opisthomastigote stages measured 3.4–12 × 1.3–4.3 μm, Giemsastained, with flagella measuring 13.8–18.7 μm. A few amastigotes (3.9–8.3 × 3.7–6.7 μm) were also observed. Fourteen larvae fed with a suspension of flagellates were found later to be infected with the protozoan. No flagellate infections were found in the hymenopteran parasitoid, Apanteles ruficus (Haliday), or the hyperparasitoid, Trichomalopsis sp.