A review of the pre-oviposition behaviour of small cabbage white butterfly, Pieris rapae(lepidoptera: Pieridae)

This paper reviews the literature concerning the ovipositional behaviour of Pieris rapae (small cabbage white butterfly) and where appropriate considers results from studies involving other butterflies. The paper considers searching behaviour, stimuli utilised in host plant finding and identification and concludes with a general section on the role of learning and prior experience in ovipositional behaviour.     

Associative learning in the ovipositional behaviour of the cabbage butterfly, Pieris rapae

ABSTRACT. When tested with familiar and novel oviposition sites, gravid female Pieris rapae (L.) tended to land on sites of the same appearance as those they had experienced 24 h earlier. This acquired preference could be reversed by subsequent e xperience. An ovipositional preference, shown by groups of insects, paralleled the landing preferences of single insects. These influences of experience were shown with intact cabbage plants of different kinds, with discs cut from the leaves of different kinds of cabbage, and with discs of blotting paper of different shades of green and blue, wetted with sinigrin solution or water. A single landing by a gravid female on paper wetted with sinigrin solution induced a landing preference for the same colour of paper in a choice test made 24 h later. Gravid females thus associated a favourable chemical stimulus of oviposition with the appearance of the acceptable site. Such learning by trial and error would facilitate host-selection from a distance. In the laboratory it induced oviposition on 'neutral' sites of the same appearance as 'host' sites.     

Interspecific egg load assessment of host plants by Pieris rapae butterflies

Egglaying responses of Pieris rapae L. butterflies to the oviposition deterring pheromone (ODP) of Pieris brassicae L. were studied in the laboratory. Choice experiments with ODP treated leaves and control leaves revealed that females perform a strong preference to lay their eggs on the control leaves. This preference is maintained even when during the experiment the control leaf becomes covered with a large number of conspecific eggs. Choice experiments with cabbage leaves with and without P. rapae eggs seem to indicate the absence of intraspecific egg load assessment of host plants in P. rapae. The deterrent effect of the ODP of P. brassicae to P. rapae females persists for at least 8 days. Behavioural observations suggest olfactory hairs as well as gustatory hairs to be involved in the perception of the ODP but electrophysiological recordings of the various chemoreceptors are necessary to confirm this. Finally the prospects of application of this pheromone/kairomone in cabbage pest control are discussed.

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Appréciation de la charge interspécifique en oeufs sur la plante hôte par Pieris rapae

Résumé La réponse au laboratoire de P. rapae à la phéromone dissuadant la ponte (ODP) de P. brassicae a été étudiée par l'oviposition. Des expériences de choix entre des feuilles traitées à l'ODP et des témoins ont montré que les femelles préfèrent nettement les feuilles témoins. Cette préférence s'est maintenue même quand les feuilles témoins ont été recouvertes d'un grand nombre d'oeufs de P. rapae. Ceci peut indiquer l'absence chez P. rapae d'une évaluation de la charge de ses propres oeufs. L'effet dissuadant du ODP de P. brassicae sur les femelles de P. rapae persiste au moins 8 jours. Les observations comportementales suggèrent que des poils olfactifs aussi bien que des poils gustatifs sont impliqués dans la perception d'ODP mais une confirmation de cette hypothèse par enregistrements électrophysiologiques est nécessaire. Les perspectives d'utilisation de cette phéromone/kairomone dans la lutte contre les insectes du chou sont examinées.

     

Long-term changes in the oviposition behaviour of the cabbage butterfly, Pieris rapae, induced by contact with plants

ABSTRACT. Contact between the tarsi and cabbage foliage was found to have important influences on the oviposition behaviour of Pieris rapae , whereas contact between the ovipositor tip and cabbage foliage showed no influence. Oviposition on a leaf disc was not influenced by the presence of previously laid eggs. Gravid female P.rapae showed an increased tendency to approach and land on host or non-host foliage, or on yellow or green cards, after tarsal contact with cabbage foliage. This effect persisted for at least 72h. It was accompanied by an increased tendency to oviposit on non-host plants, most obviously within seconds of contact with cabbage, but with some persistence after 72h. Contact with a non-host leaf (lettuce) reduced the tendency of females to land on plants, but this effect was less pronounced than the one induced by contact with cabbage. These behavioural changes were immediate as well as long-term and were not associated with changes in the ovaries, so they probably result from the direct effects of sensory input on the CNS. Such behaviour probably increased the likelihood that gravid females would locate host-plants for oviposition in the field. For tests of host-plant specificity, the implications are that the behaviour of gravid females towards an array of plants might differ according to the presence or absence of hosts, not only during the test, but also during the preceding several days.     

Physical and chemical factors influencing landing and oviposition by the cabbage root fly on host-plant models

Various plant models were used in both choice and no-choice tests in the laboratory to assess landing and oviposition preferences of the cabbage root fly,Delia radicum (L.). The main factor governing the site most suitable for landing was the conspicuousness of the object and not its shape. Oviposition was influenced considerably by the pre-conditioning of the females. Deprived females laid eggs even when denied access to both host plant chemicals and host-plant models. The dominant role of contact chemical stimuli in host acceptance was reconfirmed, but only a combination of physical and chemical stimuli appeared capable of eliciting normal oviposition. The combination of contact chemical stimuli and the presence of a stem on the test model had a synergistic effect on the numbers of eggs laid in both choice and no-choice situations. In choice bioassays, female cabbage root flies distinguished between models of different shapes, heights and sizes. The size and shape of the models appeared to be perceived in part after the flies had landed.     

Visual learning in assays of sinigrin solution as an oviposition releaser for the cabbage butterfly, Pieris rapae

Pieris rapae (L.) oviposited readily on paper wetted with sinigrin solution, if it was yellow, green, light blue or white, but not if violet, red, or black. On violet discs, feeding responses distracted the butterflies from oviposition and they often laid on neighbouring green discs which lacked sinigrin. When some discs with water and others with sinigrin solution were offered together, butterflies oviposited more on water discs of the same colour as the sinigrin discs, as opposed to those of a different colour. Within a range of sinigrin solutions tested (10–1000 ppm) the higher concentrations elicited most oviposition. Preference was slight for different concentrations applied to physically identical discs, but marked for the higher of two concentrations (100 vs 75 ppm) on discs of different but equally acceptable appearance. It was concluded that by trial-and-error, ovipositing butterflies learnt to associate the appearance of the oviposition site with its contact chemical stimuli, and that learning either increased or decreased the specificity of responses to sinigrin-treated discs, according to the design of the assay. Learning influenced preference differently in butterflies offered two as opposed to three kinds of acceptable site.

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Résumé La ponte de Pieris rapae L., phytophage spécialiste de crucifères, a été étudiée avec des rondelles de papier buvard coloré, imbibées avec une solution de sinigrine, substance spécifique, non volatile, des plantes hôtes. Les papillons ont bien pondu lors de répétitions sur papiers jaune, vert, bleu clair ou blanc, et peu sur papiers rouge, violet ou noir. Avec des rondelles violettes, la prise d'aliments a distrait de la ponte, et des oeufs ont alors été souvent pondus sur des rondelles vertes proches sans sinigrine. Quand des rondelles avec de l'eau et d'autres avec des solutions de sinigrine ont été offertes simultanément, les papillons ont pondu plus sur les rondelles imbibées d'eau de la même couleur que celles avec de la sinigrine, que sur celles d'une autre couleur. Dans la gamme des concentrations de solution de sinigrine examinées (10 à 1000 ppm les plus élevées ont induit les pontes les plus importantes. Il y a eu peu de préférence entre des rondelles de même couleur ayant des concentrations différentes, mais le choix a été net quand les rondelles étaient de couleurs différentes et pourtant acceptables, dans ces conditions la concentration la plus élevée (100 versus 75 ppm) était préférée. On peut en conclure que les papillons, par un apprentissage avec essai et erreur, lors de la ponte ont associé l'aspect du lieu de ponte avec les stimulations chimiques de contact; l'apprentissage a, soit augmenté, soit réduit la spécificité des réponses aux rondelles traitées à la sinigrine, suivant les conditions de l'expérience. La discussion examine la signification du tambourinage par les pattes antérieures comme séquence préliminaires de la ponte.

     

Differential selection of host plants by twoPieris species: the role of oviposition stimulants and deterrents

Oviposition responses ofPieris rapae L. andP. napi oleracea Harris to nine crucifers, one Capparidaceae and one Tropaeolaceae were directly compared under controlled conditions. Chemical fractions from these plants were also tested on both insects for the presence of oviposition stimulants or deterrents. The results showed that plant chemistry is a key factor in differential selection of potential hosts by thesePieris species. Some plant species were equally acceptable to bothPieris species. However,P. rapae preferred cabbage over most test plants whereasP. napi oleracea strongly preferred plant species that were avoided byP. rapae. The observed preferences were explained in most cases by the presence of stimulants and deterrents in extracts of the plants. The twoPieris species have apparently evolved differential sensitivities to the chemical stimuli that trigger or deter oviposition. The balance of positively and negatively interpreted sensory signals evoked by plant chemicals obviously plays an important role in acceptance or rejection of a plant by both species. The role of specific glucosinolates and differing structure-activity relationships is suggested.     

Perception of the oviposition deterring pheromone by tarsal and abdominal contact chemoreceptors in Pieris brassicae

Perception of the oviposition deterring pheromone by contact chemoreceptors in female Pieris brassicae was studied employing a tip recording technique. Electrophysiological responses of tarsal taste hairs to eggwash solutions show a marked increase in frequency of spikes originating from only one sensory cell. This suggests that in foretarsal taste hairs females, apart from the glucosinolate cells also possess sense cells specifically sensitive to the oviposition deterring pheromone.Morphological studies by means of the scanning electron microscope revealed that the ovipositor of P. brassicae is provided with two groups of contact chemoreceptors. Electrophysiological recordings from these sensilla indicate the presence of at least three sensory cells, one of them being a mechanoreceptor. Stimulation with eggwash evokes a slight increase in spike frequency which cannot be ascribed to one particular sense cell. This indicates that abdominal taste hairs in some way may participate in the perception of the oviposition deterring pheromone. Responses to glucosinolates do not differ significantly from control stimulations.

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Résumé Une technique d'enregistrement apical a été utilisée pour examiner la perception d'une phéromone dissuadant la ponte par les poils récepteurs chimiques de contact des femelles de Pieris brassicae. Les réponses électrophysiologiques des poils gustatifs des tarses en présence de solutions de rinçage d'oeufs présentent une fréquence marquée des potentiels d'action provenant principalement d'une cellule sensorielle. Ceci suggère que les poils gustatifs des tarses des pattes antérieures des femelles possèdent, en plus de cellules répondant aux glucosinolates, des cellules sensorielles sensibles spécialement à la phéromone dissuadant la ponte.Des études morphologiques au microscope à balayage révèlent que l'oviposition de P. brassicae est pourvu de deux groupes de chimiorécepteurs de contact. Des enregistrements électrophysiologiques de ces sensilles révèlent la présence d'au moins trois cellules sensorielles, l'une d'entre elles étant un mécanorécepteur. La stimulation avec la solution de rinçage des oeufs évoque un léger accroissement de la fréquence des potentiels d'action qui ne peut être attribué à une cellule sensorielle particulière. Ceci indique que les poils gustatifs abdominaux peuvent participer d'une certaine façon à la perception de la phéromone dissuadant la ponte. Les réponses aux glucosinolates ne diffèrent pas significativement des stimulations témoin.

     

Identificaton of UV,green and red receptors,and their projection to lamina in the cabbage butterfly,Pieris rapae

Summary The photoreceptors in the compound eye of a cabbage butterfly, Pieris rapae, were examined by conventional and intracellular-labeling electron microscopy by the use of the cobalt(III)-lysine complex as an ionized marker. Five types of spectral sensitivity were recorded intracellularly in electrophysiological experiments. They peaked at about 340, 380, 480, 560 and 620 nm, respectively. One of the distal retinula cells (R2) was a UV receptor, whereas the R4 distal retinula cell was a green receptor. The basal retinula cell, R9, was found to be a red receptor; it was localized near the basement membrane, having a bilobed cell body with an individual nucleus in each lobe. A small number of rhabdomere microvilli were present in a narrow cytoplasmic bridge connecting the two lobes. The axons of six retinula cells (R3–R8) in each ommatidium terminated at the cartridge in the lamina (short visual fiber), whereas those of the other three retinula cells, R1, R2 and R9, extended to the medulla (long visual fiber). The information from the UV and red receptors is therefore probably delivered directly to the medulla neurons, independent of that from the other spectral receptor types.     

Larval diet influence on oviposition behaviour inSpodoptera littoralis

Females ofSpodoptera littoralis Boisd. (Lepidoptera: Noctuidae) with different feeding experiences during their larval development were tested for their ovipositional response to methanol extracts of larval frass and semisynthetic diets. The effect of the following frass, diet and diet component extracts was tested: (a) frass fromS. littoralis orAgrotis segetum larvae fed on a potato-based diet; (b) frass fromS. littoralis larvae fed on a wheat germ-based diet; (c) potato and wheat germ-based diets; and (d) potatoes and wheat germ. Ovipositing females without prior experience of the potato diet were deterred by extracts of: (1) larval frass from either species fed on potato diet; (2) the potato-based diet; (3) potato. Also females with experience of the potato diet during only a part of their larval development were deterred from oviposition by frass of larvae reared on the potato diet and by the diet itself. However, for females reared on the potato diet for their entire larval development, oviposition was no longer deterred by either of the three extracts listed above. Extracts of: (1) frass from larvae of either species reared on wheat germ diet: (2) the wheat germ diet; or (3) wheat germ did not significantly affect oviposition. Females with ablated antennae were still deterred by frass extracts from larvae fed on potato diet, when they had been reared on the wheat germ diet. In feeding experiments, larvae of larval stage one and of larval stage three-four reared on either of the two diets preferred to feed on the wheat germ diet. However, the preference was significantly stronger for larvae with no prior contact with the potato diet. The effect of larval experience on the loss of oviposition-deterring activity by extracts of larval frass, diets and diet components is discussed in view of induction and selection.     

Effects of experimental design and nitrogen on cabbage butterfly oviposition

Summary To test the prediction that P. rapae egg densities increase with N fertilizer in large-scale systems as they do in model systems with potted plants, we used field experiments with Brassica oleracea var. acephala L. (collards and kale) planted in pots or large field plots, and treated with different levels of nitrogen fertilizer. In small-scale field experiments with potted kale and collards, egg densities were significantly higher on plants with high N than those with low N. But in larger scale experiments with field-grown collards, average seasonal P. rapae egg densities were not significantly correlated with leaf N content. These differences among experiments did not depend on the magnitude of the difference in foliage N levels.     

Effect of color hue and brightness of artificial oviposition substrates on the selection of oviposition site by Dacus oleae

In laboratory experiments of the choice type, olive fruit flies, Dacus oleae (Gmelin), wild and/or olivereared for a few generations, showed strong preference for oviposition in yellow and orange colored ceresin wax domes 18 mm in diameter. Green colored domes of two different hues were less preferred, while red, blue, black and white domes received a limited number of eggs when a preferred color was present. The females more frequently visited the domes of the preferred colors, which indicates that they selected them before arrival. The observed preference for certain colors like yellow and orange depended primarily on the color hue and not on the intensity of the total reflected light or on the degree to which the colored domes contrasted with the background. The females responded positively to hues reflecting maximally between 560 and 610 nm, optinum at ca. 580 nm. Hues reflecting maximally between 520 and 550 nm or above 610 nm were not very attractive while hues reflecting below 520 nm and especially between 400 and 480 nm appeared to be rather unattractive. There were indications that not only the spectral purity of a hue but also the quantity of the energy reflected within the narrow spectral region which corresponds to that hue are important for the selection of the oviposition site by this fly.

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Der einfluss von farbtönen und farbintensität künstlicher eiablagesubstrate auf ihre auswahl für die eiablage bei Dacus oleae

Zusammenfassung In Auswahlversuchen im Labor bevorzugten wilde und für einige Generationen im Labor auf Oliven gezüchtete Olivenfliegenweibchen zur Eiablage gelb und orange gefärbte Ceresinwachsdome von 18 mm Durchmesser. Grüngefärbte Dome von zwei verschiedenen Farbtönen waren weniger bevorzugt. Rote, blaue, schwarze und weisse Dome wurden mit einer begrenzten Anzahl Eiern belegt, wenn eine der bevorzugten Farben dabei war. Die Weibchen besuchten öfter die Dome mit den bevorzugten Farben, was darauf hindeutet, dass sie diese vor der Ankunft auswählten.Die beobachtete Bevorzugung für gewisse Farben wie gelb und orange hing hauptsächlich von den Farbtönen ab und nicht von der Intensität des total reflektierten Lichtes oder der Stärke des Kontrastes der farbigen Dome vom Hintergrund. Die Weibchen reagierten positiv auf Farbtöne mit einer maximalen Reflektion zwischen 560 und 610 nm mit einem Optimum bei ca. 580 nm. Farbtöne, die maximal zwischen 520 und 550 nm oder bei mehr als 610 nm reflektierten, waren nicht sehr attraktiv und Farbtöne mit einer Reflektion bei weniger als 520 nm, speziell zwischen 400 und 480 nm, scheinen nicht attraktiv zu sein. Es bestehen Hinweise dafür, dass nicht nur die Farbreinheit sondern auch die Menge der reflektierten Energie des entsprechenden Spektralabschnittes wichtig für die Auswahl der Eiablagesubstrate ist.

     

The effect of host acceptability on oviposition and egg accumulation by the small white butterfly, Pieris rapae

The influence of host‐plant acceptability on oviposition rate, egg load, internal fat storage and longevity was studied in the small white butterfly, Pieris rapae L. (Lepidoptera: Pieridae). Newly emerged females and males were presented with either cabbage (Brassica oleracea L. var. gemmifera), which is a highly acceptable host for the small white, or wallflower (Cheiranthus cheiri L.), which is much less acceptable for oviposition. Individuals were dissected when 3, 6 and 9‐days‐old. Females kept on cabbage contained fewer mature eggs than those kept on wallflower and there was no change in the load of mature eggs over the time course studied. The number of immature eggs carried did not vary with host plant species, but did fall significantly between days 6 and 9. The body fat content of individuals declined with increasing age, but the decline was slower for individuals kept on the host of low acceptability. Individuals that were allowed to spend their natural lifespan on cabbage showed similar oviposition patterns over time, where the oviposition rate started high and gradually reduced until death. However, considerable differences in oviposition pattern were found in individuals kept on wallflower, varying from that found on cabbage to no oviposition at all. The implications of these findings are discussed in the light of existing oviposition theories. This leads to the conclusion that in one species the premises of existing theories on optimization of oviposition are not mutually exclusive but rather play in concert.     

Structure,development and death of sensory cells and neurons in the pupal labial palp of the butterflies Pieris rapae L. and Pieris brassicae L. (Insecta,Lepidoptera)

Summary The development of neurons possibly related to the outgrowth of axons from the labial palp-pit organ was studied in Pieris rapae. Serial sections of six successive stages between pupation and emergence of the imago were examined with the electron microscope. At pupation the palp contains an apical scolopidial organ (ASO) and cellular strands connected to it. The ASO consists of three type-1 scolopidia, which are characterized by the presence of a ciliary 9 × 2 + 0 pattern throughout the dendritic outer segment and a ciliary dilation beneath the cap. The scolopidia show two special features: (i) the dendritic outer segments reach beyond the cap, and (ii) an intricate junctional complex develops between the dendritic inner segments and the scolopale cells. The cellular strands comprise two types of cells: (1) bipolar cells regarded as neurons due to their cytological features, and (2) enveloping cells, which are wrapped around the bipolar cells. The strands degenerate about 10 h after pupation. The sensory cells of the ASO degenerate consecutively between 28 h and 130 h after pupation. However, their enveloping cells survive and endure in the imago, which emerges about 160 h after pupation. An ASO similarly lacking sensory cells was observed in imagines of Pieris brassicae. It is hypothesized that the ASO and the bipolar neurons of the strands play a role in pathfinding of the axons of the labial palp-pit organ.Supported by the Deutsche Forschungsgemeinschaft (SFB 4/G1)     

The effect of colour of the substrate on the landing and oviposition behaviour of the cabbage root fly

Field and laboratory experiments were made in order to understand the relation between the spectral characteristic of a substrate and its attractiveness for Delia radicum (L.) (Diptera: Anthomyiidae) flies to land or oviposit. Landing females preferred substrates with high reflectance of green and particularly of yellow wavelengths, but substrates with a high proportion of the blue and green reflectance simultaneously (light blue and white) were also very attractive. Unattractive substrates had either low reflectance across the whole insect-visible spectrum (dark blue) or increased reflectance only in orange or red region of the spectrum (red) or a large proportion of UV reflectance (aluminium). Landing males were most attracted to the substrates with the highest total reflection. Oviposition attractiveness of a substrate grew with an increase in the proportion of reflectance in the blue and a decrease in the green regions of the spectrum. In addition, the oviposition attractiveness increased with increasing total reflection and contrast with the background, and decreased with a high proportion of UV reflectance.     

Effect of color properties on the selection of oviposition site by Ceratitis capitata

In laboratory experiments of the choice type, wild Mediterranean fruit flies, Ceratitis capitata (Wiedemann), originating from infested figs collected in the island of Chios, Greece, showed strong preference for oviposition in black, blue and red colored ceresin wax domes 18 mm in diameter. Green and orange domes were less preferred, while yellow and white domes received the least number of eggs when a preferred color was present. The observed preference for certain colors was found to depend on both the color hue and the intensity of the total reflected light (brightness), while the degree the colored domes contrasted with the background had little if any effect. The females visited the domes of the preferred colors most frequently, which indicates that some selection occurred before arrival on the domes.

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Zusammenfassung In Auswahlversuchen im Labor zeigten wilde Mittelmeerfruchtfliegen, Ceratitis capitata (Wiedemann), die aus infestierten Feigen der Insel Chios, Griechenland, stammten, eine starke Bevorzugung für schwarze, blaue und rote Ceresin Waxdome mit 18 mm Durchmesser. Grüne und orangefarbene Dome waren weniger bevorzugt, während gelbe und weisse Dome mit nur wenigen Eiern belegt wurden, wenn eine der bevorzugten Farben anwesend war. Die beobachtete Bevorzugung für gewisse Farben hängt vom Farbton und vom total reflektierten Licht (Helligkeit) ab, jedoch hatte die Stärke des Kontrastes der farbigen Dome vom Untergrund wenig oder keinen Einfluss. Die Weibchen besuchten öfter die Dome mit bevorzugten Farben, was darauf hindeutet, dass sie sie vor ihrer Ankunft auswählten.

     

Foliar form, colour and surface characteristics influence oviposition behaviour in the cabbage root fly Delia radicum

The effects of foliar form, colour and surface characteristics on the oviposition behaviour of the cabbage fly were investigated by presenting females with various leaf models made of paper. The models differed in shape, size, colour, surface coating, the presence of 3 dimensional folds and a stem. It was shown that in the presence of host leaf surface extracts physical factors can strongly influence oviposition behaviour. Females laid the most eggs around the base of bright green or yellow models having a stem, vertical folds and covered with a thin layer of paraffin. The vertical folds in the surface increased the chance of a behavioural transition from leaf run to stem run.

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Zusammenfassung Mit Hilfe von Papiermodellen von Kohlblättern wurde der Einfluss von visuellen und mechanischen Eigenschaften des Blattes auf das Eiablageverhalten der kleinen Kohlfliege, Delia radicum, untersucht. Die verwendeten Modelle unterschieden sich in Form, Grösse, Farbe, Oberflächen struktur und Stiel des Blattes. Es wurde gezeigt, dass physikalische Reize zusammen mit den chemischen Stoffe auf der Blattoberfläche stimulierend wirken. Ein natürliches Eiablageverhalten und die stärkste Eiablage wurde durch ein Modell ausgelöst, welches sich durch leuchtend grüne Farbe, Stiel und vertikale Falten und einen Paraffinnüberzug auszeichnete.

     

Pattern of spatial distribution of the common cabbage butterfly,Pieris rapae in a cabbage farm

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Contributions from the Entomological Laboratory, Kyoto University, No. 203.     

The role of glucosinolates and their hydrolysis products in oviposition and host-plant finding by cabbage webworm, Hellula undalis

The cabbage webworm, Hellula undalis (Fabricius) (Lepidoptera: Pyralidae), a tropical pest on crucifers (Brassicaceae), differentiated among host-plant species for oviposition in laboratory and field tests. White mustard, Sinapis alba (L.) var. Selinda, was the preferred host-plant, followed by Brassica juncea (L.) Czern. et. Coss var. Canadian brown mustard, and pak-choi, Brassica campestris L. ssp. chinensis var. Joi Choi, Black Behi and Bai Tsai. Glucosinolates (GS), secondary plant compounds characteristic to the Cruciferae plant family, and their breakdown products were analyzed by using HPLC and GC-MS-techniques. Species differed in GS composition and concentration. Content of GS was highest in S. alba with progressively lower contents detected in B. juncea and B. chinensis. The aromatic GS, 4-hydroxybenzyl-GS and benzyl-GS, were detected in S. alba. In B. juncea the alkenyl GS, allyl-GS, dominated, whereas in varieties of B. chinensis indolyl and alkenyl GS predominated. Oviposition of H. undalis females on the non-host-plant Vigna unguiculata ssp. sesquipedalis (L.) Fruwirth was stimulated by application of GS extracts from the crucifer species; the extract from S. alba was preferred, followed by extracts from B. juncea and B. chinensis. Hydrolysis of GS in the plant extract from B. chinensis causes loss of the oviposition stimulatory effect of the extract. Application of the GS, allyl-GS, and benzyl-GS also stimulated oviposition by H. undalis. Significantly more eggs were laid on leaves treated with the aromatic GS, benzyl-GS, than with the alkenyl GS, allyl-GS. Host-plant odor attracted H. undalis females but not males, in behavioral assays conducted in a Y-tube olfactometer. Low concentrations of the GS hydrolysis product, allyl-isothiocyanate, induced anemotaxis of females, but a high concentration of allyl-isothiocyanate was repellent. Oviposition by H. undalis females was not stimulated by host-plant volatiles. Females laid eggs on inserted traps and the walls of the Y-tube regardless of presence or absence of host-plant odor. The relevance of these results in the context of crucifer-insect interactions is discussed.