Behavioural and chemosensory responses of the turnip root fly (Delia floralis) to glucosinolates

This study investigates the behavioural and neural mechanisms involved in the oviposition behaviour of the turnip root fly,Delia floralis (Fallen). Behavioural studies showed that glucosinolates modulated the oviposition behaviour of the flies on artificial leaves as well as the number of eggs laid in the soil at the base of these leaves. Electrophysiological responses to glucosinolates were obtained from type A and type D sensilla on the prothoracic and mesothoracic tarsi, as well as from the long contact sensilla on the labellum. The neural responses from these sensilla were positively correlated with the oviposition behaviour of the flies and with the number of eggs laid. Of the eleven glucosinolates tested in the behavioural and electrophysiological tests, the flies were most responsive to glucobrassicanapin, gluconapin and glucobrassicin. The type D tarsal sensilla were more responsive to the glucosinolates than either the type A tarsal sensilla or the labellar sensilla. The structure-activity investigations showed that slight modifications to the chemical composition of the glucosinolates resulted in changes in neural activity.     

Effects of plant nutrition on the balance of insect relevant cardenolides and glucosinolates in Erysimum cheiranthoides

The possible effects of environmental stress on plant chemistry that are important to herbivorous insects were examined by growing a wild crucifer, Erysimum cheiranthoides, under different nutrient regimes. Oviposition by the cabbage butterfly, Pieris rapae, is thought to be affected by the balance of glucosinolates (stimulants) and cardenolides (deterrents) at the surface of leaves. E. cheiranthoides seedlings were provided with three levels of nitrogen and two levels of sulfur for a period of 15 days before analysis of semiochemicals in whole leaf tissue and at the surface of the foliage. The ratio of cardenolides to glucosinolates in the plants at elevated C/N ratios followed the carbon/nutrient balance hypothesis. However, a high nitrogen supply enhanced biomass production to the extent that concentrations of secondary compounds were unchanged or reduced. The concentration of glucosinolates (glucoiberin and glucocheirolin) at the surface was positively related to whole tissue levels. However, cardenolide (erysimoside and erychroside) concentrations, which were highest in leaf tissue of nitrogen-deficient plants, had the lowest surface levels on foliage of these plants. Possible reasons for differential expression of cardenolides and glucosinolates in a plant as a result of nutrient deficiency are discussed.     

Comparison of the egg-laying behaviour and electrophysiological responses of Delia radicum and Delia floralis to cabbage leaf compounds

Abstract.  The behaviour and the sensitivity of adult cabbage root fly, Delia radicum and turnip root fly, Delia floralis are compared with host-plant extracts and isolated crucifer compounds previously identified as oviposition stimulants for D. radicum . The oviposition behaviour of both species is similar; 7–10-day-old females are stimulated to lay eggs by the methanol extract of cauliflower leaves that contains thia-triaza-fluorenes (CIF) as well as glucosinolates. The glucosinolate fraction is mainly composed of glucobrassicin, which alone stimulate both fly species to lay eggs. The C₅ and D_3,4 sensilla on the prothoracic tarsae of newly-emerged D. radicum contain neurones sensitive to the glucosinolate fractions tested and to glucobrassicin, whereas the CIF specifically stimulate a neurone in the C₅ sensillum. By contrast, newly-emerged D. floralis respond less to glucosinolates, especially to glucobrassicin, and have sensitive neurones to CIF in other sensilla than D. radicum . Recordings are also made from the longest sensilla present on the labellum because they are apparently sensitive to glucosinolates. By contrast to earlier investigations, no remarkable phasic-tonic responses of these neurones are seen. The two species are difficult to discriminate visually, have the same host plants, show identical host-selection behaviour, apparently respond to the same physical and chemical properties of their host-plants, but have a clearly different distribution of receptor neurones in the tarsal sensilla.     

Contact chemoreception related to host selection and oviposition behaviour in the monarch butterfly, Danaus plexippus

Abstract. Behavioural events during host selection by ovipositing monarch butterflies (Danaus plexippus (L.), Danainae, Nymphalidae) include tapping the leaf surface with fore-tarsi and touching this surface with mid-tarsi (‘drumming’) and antennae. Flavonoids identified from host plant extracts are known to stimulate oviposition. Scanning electron microscopy revealed the presence of contact-chemoreceptor sensilla on all appendages that contact the leaf surface. This electrophysiological study was conducted to identify the contact chemoreceptors that are sensitive to the known oviposition stimuli and are therefore probably involved in host recognition. Receptor cells of conspicuous sensilla grouped in clusters on fore-tarsi of females were sensitive to the behaviourally active butanol fraction of host plant (Asclepias curassavica) extract. However, these receptors generally had low sensitivity to three oviposition-stimulating flavonoids identified from this fraction, but they were also sensitive to the butanol fraction of a non-host (Brassica oleracea). Chemoreceptors in sensilla of the tarsomers 2–4 of the mid-legs also responded to the behaviourally active fraction of host plant extract and showed some sensitivity to two of the flavonoids that stimulate oviposition. Similar results were obtained from receptor cells in sensilla on the tip of the antennae. Most of these sensilla had cells responding to the butanol fraction of A. curassavica extract but only 25% of them were also sensitive to one of the behaviourally active flavonoids. These electrophysiological results, in combination with behavioural observations, suggest that host selection in monarch butterflies relies on a complex pattern of peripheral sensory information from several types of tarsal and antennal contact chemoreceptors.     

Oviposition and tarsal chemoreceptors of the cabbage root fly are stimulated by glucosinolates and host plant extracts

The role of glucosinolates in the oviposition behaviour of the cabbage root fly,Delia radicum (L.) (Diptera, Anthomyiidae) was investigated using egg counts and electrophysiological recordings from tarsal contact chemoreceptors. The glucosinolates present both inside and on the surface of cauliflower leaves were determined. The total amounts obtained with the two methods differed by a factor of 100. The extract of the leaf surface contained about 60 μg per g leaf extracted (gle), the total leaf extract 7.5 mg per gle. The glucosinolate patterns of the two extracts were qualitatively similar, but the ratios of the content of individual glucosinolates showed considerable differences. The D sensilla on segment 3 and 4 of the tarsus ofD. radicum females were shown to contain a sensitive receptor cell for glucosinolates. In contrast, the receptor cells of the D sensilla of the other segments did not respond in a dose dependent way to these compounds. The glucosinolate receptors were found to be especially sensitive to glucobrassicin, gluconasturtiin and glucobrassicanapin with thresholds of about 10⁻⁸ M to 10⁻⁹ M. Large differences (up to two orders of magnitude) were observed among the different glucosinolates. A significant correlation was found between the behavioural discrimination index and the electrophysiological results. But no obvious correlation existed between the chemical nature of the glucosinolate side chain (e.g. indole, aromatic and aliphatic groups), and their stimulatory activity. However, a significant correlation was found between the overall length of the side chain and the biological activity. Although the flies discriminated clearly between model leaves with and without glucosinolates, a clear dose response curve was only obtained for the indole glucosinolate glucobrassicin. Since the most stimulatory fraction of the surface extract contained no glucosinolates, it was concluded that other compounds, in addition to glucosinolates, do play an important role for the stimulation of oviposition.     

Comparative morphology of the prothoracic leg in heliconian butterflies: Tracing size allometry,podite fusions and losses in ontogeny and phylogeny

Prothoracic legs of heliconian butterflies (Nymphalidae, Heliconiinae, Heliconiini) are reduced in size compared to mesothoracic and metathoracic legs. They have no apparent function in males, but are used by females for drumming on host plants, a behavior related to oviposition site selection. Here, taking into account all recognized lineages of heliconian butterflies, we described their tarsi using optical and scanning electron microscopy and searched for podite fusions and losses, and analyzed allometry at the static, ontogenetic and phylogenetic levels. Female tarsi were similar, club-shaped, showing from four to five tarsomeres, each bearing sensilla chaetica and trichodea. Male tarsi were cylindrical, formed from five (early diverging lineages) to one (descendant lineages) either partially or totally fused tarsomeres, all deprived of sensilla. Pretarsi were reduced in both sexes, in some species being either vestigial or absent. Tarsal lengths were smaller for males in almost all species. An abrupt decrease in size was detected for the prothoracic legs during molting to the last larval instar at both histological and morphometric levels. In both sexes, most allometric coefficients found at the population level for the prothoracic legs were negative compared to the mesothoracic leg and also to wings. Prothoracic tarsi decreased proportionally in size over evolutionary time; the largest and smallest values being found for nodes of the oldest and youngest lineages, respectively. Our results demonstrate that evolution of the prothoracic leg in heliconian butterflies has been based on losses and fusions of podites, in association with negative size allometry at static, ontogenetic and phylogenetic levels. These processes have been more pronounced in males. Our study provided further support to the hypothesis that evolution of these leg structures is driven by females, by changing their use from walking to drumming during oviposition site selection. In males the leg would have been selected against due to absence of function and thus progressively reduced in size, in association with podites fusions and lost.     

Specialist deterrent chemoreceptors enable Pieris caterpillars to discriminate between chemically different deterrents

Pieris butterflies (Lepidoptera: Pieridae) are specialist herbivores of cruciferous plants. They exploit glucosinolates, secondary plant metabolites chemotaxonomically characteristic for this plant family, as token stimuli. In addition to particular glucosinolates, some genera of the Cruciferae contain cardenolides, steroidal allelochemicals that act as potent feeding and oviposition deterrents to several Pieris species. We investigated the sensory mechanisms by which these compounds are perceived in larvae. Pieris caterpillars and many other lepidopterous species are endowed with so-called generalist deterrent receptors, that respond to a broad spectrum of secondary plant substances. In Pieris caterpillars we found a second type of deterrent chemoreceptor in maxillary styloconic taste sensilla. This neuron is very sensitive to cardenolides (threshold 0.1–0.3 M). The generalist deterrent receptor also responds to these substances but its threshold lies at 50–100× higher concentrations. In behavioural preference experiments Pieris brassicae L. caterpillars preferred cardenolide-treated cabbage leaf discs when confronted with a choice between them and a deterrent substance that does not occur in the Brassicaceae. The cardenolides acted as potent deterrents when offered against untreated cabbage leaf discs. This demonstrates that the balance of activity elicited in the two types of deterrent chemoreceptors determines the behavioural decision.     

Behavioral and chemosensory responses to a host recognition cue by larvae of <Emphasis Type="Italic">Pieris rapae</Emphasis>

Larvae of the cabbage white Pieris rapae are specialists on plants belonging to the family Brassicaceae (Cruciferae). Adult females have been shown to use the glucosinolate gluconasturtiin (phenylethylglucosinolate) as a recognition cue for cruciferous plants, so they can identify an appropriate host for oviposition (Huang and Renwick in J Chem Ecol 20:1025–1037, 1994). Here, we report our results from a study of the role of this glucosinolate in feeding preferences of P. rapae larvae. The larvae were allowed to choose between leaf disks from the non-host cowpea Vigna sinensis (Fabaceae) that were treated with pure gluconasturtiin in solvent, or solvent alone. Our results showed that gluconasturtiin is a feeding stimulant for P. rapae larvae. A series of chemosensory ablations revealed that this response is mediated by one set of taste sensilla, the sensilla styloconica. Electrophysiological tip recordings revealed two neurons in the lateral sensillum styloconicum that are sensitive to gluconasturtiin. These neurons show significantly higher firing frequencies with 4 mM gluconasturtiin added to the recording pipette than for recording solution alone. We propose that the sensitivity to gluconasturtiin shown by these two taste neurons is an important contributor to the animals behavioral preference for this compound.     

Reproductive strategies and parasitization behavior of Ageniaspis citricola, a parasitoid of the citrus leafminer Phyllocnistis citrella

We describe the number, distribution, and function of sensilla located on different organs of Lobesia botrana (Lepidoptera: Tortricidae) females using scanning electron microscopy, selective staining, and contact electrophysiology. The tarsi of the prothoracic legs bear contact chemo‐mechanoreceptor sensilla chaetica (5–13 per tarsomere), arranged in rings mainly concentrated on ventral surfaces, and different mechanosensory structures (sensilla chaetica, sensilla squamiformia, sensilla campaniformia, and spines). A single contact chemo‐mechanoreceptor sensillum chaeticum is present between the claws on the pretarsus. The ventral surface of the ovipositor lobes is covered with numerous mechanosensory sensilla chaetica of different types, out of which 10 have a contact chemosensory function. Putative contact chemo‐mechanoreceptor sensilla were also observed on the proboscis and antenna. Longitudinal rows of alternated sensilla styloconica and basiconica are present on the distal part of the proboscis, and rings of sensilla chaetica are present at the antennal tip. The sensilla on these body parts may play different roles in the selection of an oviposition site.     

Sensing the Plant Surface Prior to Feeding and Oviposition: Differences in External Ultrastructure and Function Among Tarsi of <Emphasis Type="Italic">Heliconius erato</Emphasis>

Adult foretarsi of Heliconius erato Linnaeus (Lepidoptera, Nymphalidae) are reduced in size and are not used for walking. Foretarsi of the female have specialized sensilla that are presumably used to identify the host plant, by drumming. The mid- and hind tarsi also bear sensilla in both sexes, but these have not been described in detail, nor has their chemosensory function been determined. We described and compared the tarsi of H. erato under light and scanning electron microscopy. Behavioral experiments showed that differences in the shape, number, and size of sensilla were related to feeding and oviposition behaviors. Two types of sensillum (chaeticum and trichodeum) were found in similar numbers and size on the mid- and hind tarsi of both sexes. Sensilla on the female foretarsi act in host-plant site selection, strongly affecting oviposition rates when isolated. Male foretarsi lack sensilla, which may have been selected against due to the absence of function and thus lost. Sensilla on the mid- and hind tarsi are involved in sugar detection in both sexes, responding to an effective dose of sucrose (ED₅₀) near 0.01 M, and therefore might be used to identify food resources when the butterflies settle on flowers.     

Flavonoids from cabbage are feeding stimulants for diamondback moth larvae additional to glucosinolates: Chemoreception and behaviour

In caterpillars two styloconic contact chemoreceptors on the maxillary galea are assumed to contain the main taste receptors involved in host plant selection. The diamondback moth, Plutella xylostella L. is a specialist feeder of plants in the Brassicaceae, a plant family characterized by the biosynthesis of glucosinolates. We used pea (Pisum sativum L., Leguminosae) as a neutral non-host for a dual-choice leaf disc assay to quantify feeding stimulation by glucosinolates and flavonoids. Increasing concentrations of sinigrin resulted in significant preferences for sinigrin-treated leaf discs, with a threshold between 1 and 3 M. Millimolar concentrations of four of the five flavonol triglucosides likewise elicited a significant preference for flavonoid-treated leaf discs. A mixture of four flavonoids and sinigrin was significantly preferred over sinigrin-treated leaf discs alone. Vigorous unicellular electrophysiological responses of medial maxillary styloconic taste sensilla were observed in response to five glucosinolates (glucocapparin, sinigrin, glucobrassicin, glucoiberin, and gluconasturtiin). This medial taste neuron responded in a dose-dependent manner to a concentration series of sinigrin, with a threshold of response of ca. 1 M. The lateral sensillum styloconicum contained a neuron sensitive to sucrose, glucose, and fructose. However, no responses in the two types of maxillary styloconic sensilla to the phagostimulatory flavonoids could be detected, suggesting that other taste organs mediate chemoreception of flavonoids. We conclude that diamondback moth larvae employ a combination of biosynthetically distinct categories of feeding stimulants which allows for a higher degree of discriminatory ability than when this would be based on glucosinolates alone.     

Sensilla on antennae,ovipositor and tarsi of the larval parasitoids,Cotesia sesamiae (Cameron 1906) and Cotesia flavipes Cameron 1891 (Hymenoptera: Braconidae): a comparative scanning electron microscopy study

Two braconid parasitoids of cereal stemborers in eastern Africa, Cotesia sesamiae and Cotesia flavipes, have been shown to display a similar hierarchy of behavioural events during host recognition and acceptance. In order to understand the mechanisms underlying host recognition and acceptance, the morphology of antennal sensilla on the last antennomeres, on the ovipositor, and on the fifth tarsomere and pretarsus of the prothoracic legs tarsi were studied using scanning electron microscopy followed by selective silver nitrate staining. It appeared that female C. sesamiae and C. flavipes shared the same types and distribution of sensory receptors, which enable them to detect volatiles and contact chemical stimuli from their hosts. In both parasitoids, four types of sensilla were identified on the three terminal antennomeres: (i) non-porous sensilla trichodea likely to be involved in mechanoreception, (ii) uniporous sensilla chaetica with porous tips that have gustatory functions, (iii) multiporous sensilla placodea, which are likely to have olfactory function, and (iv) sensilla coeloconica known to have thermo-hygroreceptive function. The tarsi of both parasitoids possessed a few uniporous sensilla chaetica with porous tips, which may have gustatory functions. The distal end of the ovipositor bore numerous dome-shaped sensilla. However, there were no sensilla coeloconica or styloconica, known to have gustatory function in other parasitoid species, on the ovipositors of the two braconid wasps.     

Contact chemoreception of oviposition-stimulating glucosinolates and an oviposition-deterrent cardenolide in two subspecies of Pieris napi

Abstract. Electrophysiological responses to ten glucosinolates, oviposition stimulants isolated from their cruciferous host plants, were recorded from tarsal taste neurones of two subspecies of Pieris napi: P. napi napi L. and P. napi olerucea (Harris) (Lepidoptera: Pieridae). In the cluster of fourteen medial B-sensilla on the fifth tarsomere, strong responses to glucosinolates were recorded. Three receptors cells, identified on the basis of spike amplitude and shape, were typically active in these responses, with the cell producing the smallest spike predominating. The response intensity of the latter cell to a particular glucosinolate at 1 mm concentration depended both on the chemical structure of the stimulus and on the subspecies of insect. In P. napi napi , aromatic glucosinolates were just as effective as aliphatic glucosinolates, whereas in P. napi oleracea the long-chain aliphatic glucosinolates gluconapin and progoitrin were stronger stimuli. At 10 and 100 pg/ml concentrations, significant differences between the subspecies were found in the absolute response intensity to seven compounds. A second cell in P. napi olerucea , producing a medium-sized spike, was excited most by sinalbin, whereas in Pnupi nupi three aliphatic glucosinolates were equally effective stimulants for a similar cell. In both subspecies the cell producing the medium-sized spikes in response to glucosinolates was also highly sensitive to erychroside, an oviposition deterring cardenolide occurring in a host of P. napi olerncea. The evolutionary divergence between the two geographically separated subspecies is reflected by differences in chemosensory recognition mechanisms.     

STEPWISE EVOLUTION OF RESISTANCE TO TOXIC CARDENOLIDES VIA GENETIC SUBSTITUTIONS IN THE NA+/K+‐ATPASE OF MILKWEED BUTTERFLIES (LEPIDOPTERA: DANAINI)

Despite the monarch butterfly (Danaus plexippus) being famous for its adaptations to the defensive traits of its milkweed host plants, little is known about the macroevolution of these traits. Unlike most other animal species, monarchs are largely insensitive to cardenolides, because their target site, the sodium pump (Na⁺/K⁺‐ATPase), has evolved amino acid substitutions that reduce cardenolide binding (so‐called target site insensitivity, TSI). Because many, but not all, species of milkweed butterflies (Danaini) are associated with cardenolide‐containing host plants, we analyzed 16 species, representing all phylogenetic lineages of milkweed butterflies, for the occurrence of TSI by sequence analyses of the Na⁺/K⁺‐ATPase gene and by enzymatic assays with extracted Na⁺/K⁺‐ATPase. Here we report that sensitivity to cardenolides was reduced in a stepwise manner during the macroevolution of milkweed butterflies. Strikingly, not all Danaini typically consuming cardenolides showed TSI, but rather TSI was more strongly associated with sequestration of toxic cardenolides. Thus, the interplay between bottom‐up selection by plant compounds and top‐down selection by natural enemies can explain the evolutionary sequence of adaptations to these toxins.     

Leaf buds, a factor in host selection by Battus philenor butterflies

ABSTRACT.

• 1 Field and laboratory experiments identified a character intrinsic to Aristolochia reticulata Nutt. host plants, the terminal leaf bud, that is involved in host-selection behaviour by female pipevine swallowtail butterflies (Battus philenor L.) searching for oviposition sites.
• 2 In the field, the frequency with which females landed on non-host buds declined seasonally as the proportion of host foliage that consisted of buds decreased. Female butterflies did not land on non-host species in proportion to their abundance; rather, females landed on those non-host species whose buds resembled those of A.reticulata.
• 3 A.reticulata plants whose terminal leaf bud was concealed by plastic tape were less susceptible to oviposition in the field than were control plants.
• 4 Female butterflies released in a large, outdoor enclosure were conditioned to search for leaf buds only when exposed to a host species bearing a prominent terminal leaf bud.
• 5 The significance of conditioning of leaf-bud searching behaviour is discussed with respect to discrimination between hosts and non-hosts, between host species, and among plants within a host species.

     

Morphological and electrophysiological mapping of tarsal chemoreceptors of oviposition-deterring pheromone in Rhagoletis pomonella flies

Light microscopy and S.E.M. observations revealed that Rhagoletis pomonella female tarsi, bearing the principal receptors of oviposition-deterring fruit marking pheromone (ODP), have 3 types of chemosensilla: B, C and D. Using electrophysiological hair tip-recording techniques, we found that D chemosensilla located in pairs on distal ventrolateral portions of the 2nd, 3rd and 4th tarsomeres of each leg were highly sensitive to stimulation by the pheromone. D chemosensilla located in pairs on the 5th tarsomere of each leg were moderately sensitive to the pheromone, while the B and C chemosensilla of all tarsi were nearly or completely insensitive to it. For reasons discussed, the D chemosensilla on the prothoracic tarsi may be the most important in providing sensory input eliciting oviposition deterrence.     

Sexual dimorphism of antennal,tarsal and ovipositor chemosensilla in the African stemborer,Busseola fusca (Fuller) (Lepidoptera: Noctuidae)

The number and distribution of chemosensilla located on different organs of Busseola fusca (Fuller) (Lepidoptera: Noctuidae) males and females are described based on observations using scanning electron microscopy, selective staining with silver nitrate, and gustatory electrophysiological recording. The antennae and the fifth tarsomere of the prothoracic legs of both sexes bear chemosensilla: uniporous chaetica and multiporous trichoidea sensilla. However, there is a sexual dimorphism in the number and size of sensilla on these organs. The distal part of the ovipositor has uniporous gustatory chemosensilla of the chaetica type. The involvement of these sensilla in oviposition site selection by B. fusca is discussed.     

Morphology and function of ovipositorial and tarsal sensilla of female Asian citrus psyllid

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera:Psyllidae), is one of the most important pests of citrus plants worldwide, due to be the dominant vector of the devastating citrus disease Huanglongbing (HLB). Selection of suitable oviposition site is a crucial event of phytophagous insect life. Usually, the chemical and physical characteristics of a host plant were recognized by sensilla on the ovipositor and tarsi of a phytophagous insect after settling on a plant surface. In this study, the morphology, number, and distribution pattern of the ovipositorial and tarsal sensilla of adult female psyllids, were observed by scanning electron microscopy (SEM) techniques. The effect of these sensilla on oviposition was investigated by sensilla deactivation using hydrochloric acid (HCl). The results showed that sensilla trichoid (ST), sensilla chaetica (ChS) and sensilla basiconica (SB) were distributed on ovipositor, while sensilla trichoid (ST) were distributed on the external genitalia. Sensilla chaetica (ChS) and basiconica (SB) were mainly distributed on the end of the ovipositor back plate, and on the base of the sternum. On tarsus, sensilla trichoid (ST), sensilla chaetica (ChS), sensilla triangular (TeS) and sensilla ear ball (SE) were observed. However, whole tarsal segments were covered with Böhm's mane, which was arranged in a circular line. Oviposition assay revealed that a significantly lower number of eggs were laid on the Murraya paniculata seedlings confined by the psyllids with deactivated ovipositorial sensilla followed by protarsal sensilla, mesotarsal sensilla and hindtarsal sensilla. These results suggested that the ovipositorial and tarsal sensilla of citrus psyllid have an important role in the oviposition.     

Engineering of benzylglucosinolate in tobacco provides proof-of-concept for dead-end trap crops genetically modified to attract Plutella xylostella (diamondback moth)

Glucosinolates are biologically active natural products characteristic of crucifers, including oilseed rape, cabbage vegetables and the model plant Arabidopsis thaliana. Crucifer‐specialist insect herbivores, like the economically important pest Plutella xylostella (diamondback moth), frequently use glucosinolates as oviposition stimuli. This suggests that the transfer of a glucosinolate biosynthetic pathway to a non‐crucifer would stimulate oviposition on an otherwise non‐attractive plant. Here, we demonstrate that stable genetic transfer of the six‐step benzylglucosinolate pathway from A. thaliana to Nicotiana tabacum (tobacco) results in the production of benzylglucosinolate without causing morphological alterations. Benzylglucosinolate‐producing tobacco plants were more attractive for oviposition by female P. xylostella moths than wild‐type tobacco plants. As newly hatched P. xylostella larvae were unable to survive on tobacco, these results represent a proof‐of‐concept strategy for rendering non‐host plants attractive for oviposition by specialist herbivores with the long‐term goal of generating efficient dead‐end trap crops for agriculturally important pests.     

The chemosensilla on tarsi of Locusta migratoria (Orthoptera: Acrididae): Distribution,ultrastructure, expression of chemosensory proteins

The chemosensilla on the tarsi of Locusta migratoria were mapped using light microscopy, as well as scanning and transmission electron microscopy. Only chemosensilla chaetica were found on the tarsi. On the basis of their ultrastructure, these can be grouped into three main subtypes: short, long, and sunken sensilla chaetica. Short sensilla chaetica can be further divided into two groups containing 6 or 7 neurons. Long sensilla chaetica are mainly located on the lateral surface of the tarsi. Short sensilla chaetica were mainly found on the dorsal surface of the tarsi. Sunken sensilla chaetica were only found on the ventral surface, such as the pulvilli and arolium. Immunocytochemical localization of chemosensory protein (CSP) was performed on ultrathin sections of chemosensilla on tarsi. The antiserum against LmigCSP‐II intensively labeled all three types of sensilla chaetica. Gold granules were concentrated in the outer sensillum lymph surrounding the dendrite sheath, while the inner sensillum lymph containing dendrite branches was never labeled. Massive labeling with the anti‐LmigCSP‐II was also found in cuticle of the pulvilli on the ventral surface of tarsi. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.