Marking of host fruit by maleRhagoletis boycei Cresson flies (Diptera: Tephritidae) and its effect on egg-laying

MaleRhagoletis boycei flies (Cresson) have been shown previously to guard egg-laying punctures on host walnut (Juglans major) fruit. During their tenure,R. boycei males were observed to dip the posterior portion of their abdomen repeatedly toward the fruit surface. Closeup video analysis revealed that, during this dipping behavior, a clear viscous substance emanating from the cercus was deposited directly on the fruit. Laboratory assays indicated that the rate of abdomen-dipping was significantly higher on fruit bearing simulated egg-laying punctures than on control fruit and significantly higher in the area of the puncture than elsewhere on the fruit. In a final experiment, the occurrence of abdomen-dipping in the vicinity of a puncture was manipulated independently on separate punctures on the same fruit. On such fruit and in the absence of males, previously mated, reproductively mature females attempted oviposition significantly more often in or near a puncture exposed to males than in or near an unexposed control puncture. Possible functions of the putative male-marking behavior from the perspectives of both male and female are discussed.     

Mechanism and effectiveness of safflower oil against female Queensland fruit fly Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), infests many horticultural fruit crops in the eastern part of Australia. Farmers usually apply synthetic insecticides to control this pest. Little is known on the use of plant products especially vegetable oils for fruit fly control although they are considered to be safer than synthetic insecticides. In this study, safflower oil was investigated for its mechanism and effectiveness against female B. tryoni. In a laboratory test, safflower oil treatments (2.5 and 5.0 ml l^?1) reduced the number of fly punctures on treated artificial fruits, no matter whether pre‐punctures were present or absent. Safflower oil treatments also reduced the number of fly landings and eggs laid, but only when the treated artificial fruits were without pre‐punctures. These results confirmed that safflower oil is active against female B. tryoni mainly by preventing this fruit fly from making oviposition punctures, not by discouraging them from depositing eggs or by repelling them. The slippery nature of safflower oil is considered to be responsible for a reduction in the susceptibility of artificial fruit to fruit fly punctures. Further investigation using fruit‐bearing tomato plants (a no‐choice test) in a glasshouse situation revealed that safflower oil application at concentrations of 10 and 15 ml l^?1 reduced the number of oviposition punctures but failed to reduce the number of eggs laid. To increase efficacy of safflower oil under field conditions, multiple tools may be needed to reduce fruit fly populations and oviposition behaviour, such as the addition of trap‐crops, provision of artificial oviposition sites, or mixing the insecticides with the oil.     

Oviposition in Culicoides impunctatus under laboratory conditions

We present a laboratory-based examination of oviposition preference in the Scottish biting midge, Culicoides impunctatus (Diptera: Ceratopogonidae). A variety of oviposition substrates were screened in no-choice and choice bioassays for efficacy in eliciting an egg-laying response. Both upper-layer photosynthetic Sphagnum spp. moss and Juncus articulatus infusions were identified as producing increased oviposition under no-choice conditions. During choice trials against a control of damp cottonwool, upper-layer Sphagnum spp. moss produced a significantly greater egg-laying response. These conclusions are interpreted in terms of possible cues involved in oviposition site selection and assessed for future use in colonisation of this troublesome species.     

Deposition and longevity of oviposition-deterring pheromone in the cabbage seed weevil

Abstract The cabbage seed weevil ( Ceutorhynchus assimilis Payk.) lays eggs singly into pods of oilseed rape ( Brassica napus L.) through punctures bored with the mouthparts, preferring pods not recently used for oviposition. A simple new choice test has been used to test individual components of egg-laying behaviour for their effect on oviposition site selection. It is confirmed that an oviposition-deterring pheromone (ODP) is deposited during abdomen brushing of the pod which follows egg-laying. Neither pin punctures, weevil feeding punctures, oviposition punctures nor eggs had any deterrent effect. Pods walked on by female weevils were not avoided by those laying eggs. Observations suggest that the ODP is sensed by contact chemoreceptors on the antennae. The deterrent effect lasted only 1–2 h. The implications of these findings on the adaptive significance of the pheromone and its possible use in pest control are discussed.     

Tarsal contact chemoreceptor for the host marking pheromone of the cherry fruit fly, Rhagoletis cerasi: responses to natural and synthetic compounds

Abstract. The European cherry fruit fly (Rhagoletis cerasi L.; Diptera, Tephritidae) marks cherries (Prunus avium L.) after oviposition with a host marking pheromone (HMP). The marking trail prevents additional oviposition by the same or other females into the same fruit. On the ventral side of the tarsi of both sexes, contact-chemoreceptor sensilla were identified which contain a receptor cell selectively sensitive to HMP. The HMP receptors of males were slightly more sensitive than those of females, suggesting that the more general term ‘host-marking pheromone’ is more appropriate than the previously used ‘oviposition deterring pheromone (ODP)’. The four structural isomers of the HMP, N(15R, S(β-glucopyranosyl)-oxy-8RS-hydroxypalmitoyl)-taurine, and various derivatives were synthesized and tested in an electrophysiological bioassay. Both the 8R,15R and the 8S,15RS isomers of the HMP were equally active with a threshold of about 2 times 10^-10M, and were shown to be present in the female faeces in similar proportions. The two 15S HMP isomers were about 13 times less active. Testing synthetic derivatives of the HMP molecule revealed that the presence of the four moieties of the molecule are important for the activity: taurine, palmitic acid, C₍₈₎ hydroxyl group, and glucose (C₍₁₅₎). The chain length of the fatty acid, the hydroxyl group at C₍₈₎ and the position of glucose at C₍₁₅₎ also influenced the activity. Only minor loss of activity (factor 2) relative to the natural molecule was observed when the methyl group in the C₍₁₅₎ position was removed. The removal of the β-glycosidically linked glucose (replaced by a hydroxyl group) resulted in about a 4-fold loss of activity. The cation of the HMP molecule seemed to have no effect on its activity, whereas both low and high pH reduced it significantly. Based on these results, field experiments have been initiated to control oviposition by cherry fruit flies on cherries applying the 15-desmethyl-HMP derivative.     

Influence of Conspecific Presence, Experience, and Host Quality on Oviposition Behavior and Clutch Size Determination in Anastrepha ludens (Diptera: Tephritidae)

Females of some insect species adjust the number of ovipositions and clutch size adaptively depending on conspecific density and probably experience. In a series of three experiments, we examined the effect of the presence of conspecifics, host quality, and oviposition experience on oviposition behavior and clutch size determination by females of the polyphagous fruit fly Anastrepha ludens (Diptera: Tephritidae). In the first experiment, we determined that grouped (eight females per cage) A. ludens females tended to visit and oviposit in more hosts than did solitary females probably as a result of stimulation by the presence of conspecifics. We also determined that females with previous oviposition experience visited and oviposited in more hosts than inexperienced ones. Importantly, when females were grouped, we observed significantly more landings on unoccupied hosts (i.e., devoid of flies) than on occupied ones (i.e., with at least one fly on it). However, oviposition experience, and not female density, was the most important factor affecting clutch size. Naive females deposited larger egg clutches than experienced ones. In the second experiment, we found that oviposition experience and host quality (i.e., clean fruit or fruit covered with a host marking pheromone [HMP] extract), influenced clutch size and the decision of females to defend or not defend the host. Clutch size and number of fights were greater on clean than on HMP-marked hosts. In the third experiment, we observed that host quality (i.e., size) played a significant role with regard to the number of female fights, host marking behavior, and clutch size. Specifically, females fought and dragged their aculeus longer on small- and medium-sized hosts than on large ones. But this behavior varied according to whether females were kept alone or grouped. Clutch size was greatest in the largest hosts. Considering all the above, we believe that the observed increase in ovipositional activity by grouped A. ludens females can be attributed to competition through mutual interference and not social facilitation as has been reported in other tephritid species.     

共生菌通过氧气浓度调控果蝇产卵偏嗜性

【目的】研究东方醋杆菌(Acetobacter orientalis)和短小乳杆菌(Lactobacillus brevis)通过氧气浓度调控黑腹果蝇(Drosophila melanogaster)产卵的偏嗜性,并研究其对后代存活率和发育历期的生物学意义。【方法】利用双相选择装置解析果蝇产卵行为。利用分光光度仪和pH计测量细菌的OD值与pH值。通过改变果蝇的视觉、味觉和嗅觉感官以检测介导果蝇产卵行为的感觉系统。用后代的发育历期与存活率评价其生物学意义。【结果】果蝇产卵对东方醋杆菌具有趋避性,产卵指数为–0.76,对短小乳杆菌具有趋向性,产卵指数为0.5,并且二者接种比例决定了果蝇的产卵选择。氧气作为一个调节因子,可改变果蝇对东方醋杆菌和短小乳杆菌的产卵偏嗜性。氧气是东方醋杆菌生长必需的条件,有氧培养的OD值为1.3,而无氧培养的OD值为0.4。氧气是短小乳杆菌生长非必需的条件,有氧和无氧培养的OD值均为2.2。破坏嗅觉可严重地影响果蝇对细菌的产卵偏嗜性。东方醋杆菌和短小乳杆菌均促进了果蝇的生长,分别提高存活率1倍和1.5倍,分别缩短果蝇发育历期1 d和2 d。【结论】东方醋杆菌和短小...     

The choice of oviposition site and the effects of density and oviposition timing on survivorship in<Emphasis Type="Italic"> Rana japonica</Emphasis>

In species that lack parental care and whose larvae are restricted to a given space throughout development, choice of egg-laying or reproductive sites often greatly influences fitness. Furthermore, reproductive success of individuals may be affected not only by conditions of the breeding area but also by the time when they start to breed, because intraspecific variation in the timing of breeding may result in asymmetric competition between larvae. We addressed these issues in an experimental and field study of the Japanese brown frog, Rana japonica. We tested whether the survival success of larvae decreased with an increase in the number of deposited egg masses and with a greater delay in oviposition. We found that the number of egg masses and timing of oviposition together significantly predicted larval survival per clutch. Moreover, we observed the natural oviposition of R. japonica to examine the prediction that if the density of larvae and the timing of oviposition affect survivorship of larvae, R. japonica will avoid depositing eggs in pools in which egg masses have already been deposited. We found that for small pools only, R. japonica tended to favor oviposition at unoccupied pools (those lacking egg masses and larvae) in the spawning season. For large pools, however, adults favored those already occupied by egg masses in the spawning period. The density of egg masses and tadpoles or the timing of oviposition may have less effect on spawning or the survival of tadpoles in large pools than in small pools.     

Differential circular RNAs expression in ovary during oviposition in honey bees

Circular RNAs (circRNAs) are non-coding RNAs newly identified and play important roles in RNA regulation. The mechanism and function of circRNAs have been reported in some species. However, little is known regarding circRNAs in honey bees. In this study, we analyzed circRNAs through bioinformatics, and predicted 12,211 circRNAs in the ovary of honey bee queens. 1340, 175 and 100 circRNAs were differentially expressed in comparisons of egg-laying queens vs virgin queens, egg-laying inhibited queens vs egg-laying queens and egg-laying recovery queens vs egg-laying inhibited queens. Further, functional annotation of differentially expressed circRNAs revealed several pathways that are closely related to ovary activation and oviposition, including insulin secretion and calcium signaling pathways. Moreover, the potential interactions among circRNAs, miRNAs, lncRNAs and mRNAs were investigated. Ame_circ_0005197 and ame_circ_0016640 were observed to sponge several reproductive related miRNAs. These findings demonstrate that circRNAs have potential effects in ovary activation and oviposition of honey bees.     

柑橘大实蝇对不同柑橘品种的产卵偏好和幼虫取食选择

【目的】掌握柑橘大实蝇Bactrocera minax对不同品种柑橘的产卵偏好,以及与幼虫取食喜嗜性的关系。【方法】我们用五点取样法分别调查了自然条件下不同品种柑橘果园的虫果率,统计了各品种柑橘虫果基半部和端半部产卵痕量和卵量,并在实验室内采用培养皿桔瓣选择法研究了其幼虫对不同柑橘品种果实的取食选择。【结果】在未采取防控措施的情况下,果树面朝杂树林的方位虫果率显著高于其他方位;同一片受害柑橘园内,不同柑橘品种的虫果率为脐橙Citrus sinensis cv. Navel、酸橙C. aurantium＞冰糖橙C. sinensis cv. Bingtang、天草(Amakusa)、蜜橘C. reticulata cv. Satsuma＞沙田柚C. maxima cv. Shatian＞椪柑C. reticulata cv. Ponkan;柑橘大实蝇产卵痕数和卵量均为橙类（脐橙、酸橙和冰糖橙）大于橘类（天草、蜜橘和椪柑）和沙田柚（P＜0.05）;除蜜橘外,所调查的其他柑橘品种端半部的产卵痕数显著多于基半部（P＜0.05）;幼虫对不同品种柑橘橘瓣肉的取食选择顺序依次为：脐橙、酸橙＞冰糖橙＞天草、南橘C. reticulata cv. Nanju＞蜜橘＞椪柑＞沙田柚。【结论】结果提示,柑橘大实蝇成虫偏向于选择幼虫所喜嗜的橙类品种产卵,且产卵量更多。     

Comparison of oviposition behavior of a solitary and a gregarious parasitoid (Hymenoptera: Mymaridae)

Anaphes victus Huber andAnaphes listronoti Huber (Hymenoptera: Mymaridae) are respectively solitary and gregarious egg parasitoids of the carrot weevil,Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae). We made detailed ethograms of the oviposition behavior on unparasitized and parasitized hosts for the two species. We then compared the behavior of virgin and mated females for the oviposition of male and female progenies. The two species did not always oviposit after insertion of the ovipositor, but these punctures without oviposition could be readily differentiated from oviposition.A. victus oviposited only once by puncture, whileA. listronoti deposited one to three eggs during the same sequence. The variability of the duration of the various components was generally lower for a given female than between females. Two components, the abdominal vibrations and the pause, were significantly shorter in ovipositions that resulted in male progency for the two species. However, an important overlap in duration prevents using these differences to sex the progeny at oviposition. Virgin females of both species, although capable of producing only males, exhibited both behaviors. Parasitized hosts were recognized through internal and external markings that were used in host discrimination.     

Is a mango just a mango? Testing within-fruit oviposition site choice and larval performance of a highly polyphagous fruit fly

For fruit flies, fully ripe fruit is preferred for adult oviposition and is superior for offspring performance over unripe or ripening fruit. Because not all parts of a single fruit ripen simultaneously, the opportunity exists for adult fruit flies to selectively choose riper parts of a fruit for oviposition and such selection, if it occurs, could positively influence offspring performance. Such fine scale host variation is rarely considered in fruit fly ecology, however, especially for polyphagous species which are, by definition, considered to be generalist host users. Here we study the adult oviposition preference/larval performance relationship of the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), a highly polyphagous pest species, at the “within-fruit” level to see if such a host use pattern occurs. We recorded the number of oviposition attempts that female flies made into three fruit portions (top, middle and bottom), and larval behavior and development within different fruit portions for ripening (color change) and fully-ripe mango, Mangifera indica L. (Anacardiaceae). Results indicate that female B. dorsalis do not oviposit uniformly across a mango fruit, but lay most often in the top (i.e., stalk end) of fruit and least in the bottom portion, regardless of ripening stage. There was no evidence of larval feeding site preference or performance (development time, pupal weight, percent pupation) being influenced by fruit portion, within or across the fruit ripening stages. There was, however, a very significant effect on adult emergence rate from pupae, with adult emergence rate from pupae from the bottom of ripening mango being approximately only 50% of the adult emergence rate from the top of ripening fruit, or from both the top and bottom of fully-ripe fruit. Differences in mechanical (firmness) and chemical (total soluble solids, titratable acidity, total non-structural carbohydrates) traits between different fruit portions were correlated with adult fruit utilisation. Our results support a positive adult preference/offspring performance relationship at within-fruit level for B. dorsalis. The fine level of host discrimination exhibited by B. dorsalis is at odds with the general perception that, as a polyphagous herbivore, the fly should show very little discrimination in its host use behavior.     

Oviposition Marking Behavior of <Emphasis Type="Italic">Diachasma alloeum</Emphasis>, (Hymenoptera: Braconidae), Parasitizing <Emphasis Type="Italic">Rhagoletis pomonella</Emphasis>, (Diptera: Tephritidae)

Diachasma alloeum (Muesebeck) (Hymenoptera: Braconidae) is a solitary larval endoparasitoid attacking Rhagoletis (Diptera: Tephritidae) species. Rhagoletis pomonella (Walsh) mark the surface of fruit after oviposition with an oviposition marking pheromone (OMP) which deters conspecific female flies. Herein we demonstrate that female D. alloeum wasps reared from either apple or hawthorn race R. pomenella larvae also deposit an OMP that reduces oviposition by conspecific female wasps. Significantly fewer wasps accepted fruit that had received prior wasp oviposition and OMP or OMP alone without oviposition compared with control fruit for a minimum of 7 days on both fruit types. Rinsing fruit with a 50% ethanol solution appeared to remove the OMP rendering fruit more acceptable for oviposition than marked fruit that was not rinsed. Wasps of each host race were able to detect and avoid the OMP of the sister race and fruit substrate type did not affect wasp response to the pheromone. The possibility of an internal marker deposited during oviposition is also discussed.     

Use of fruit wounds in oviposition by Mediterranean fruit flies

Casual observations suggested that female Mediterranean fruit flies (Ceratitis capitata Wiedemann) exploit fruit wounds (including pre-existing oviposition punctures) as oviposition sites. This behaviour was quantified under field conditions in a citrus grove on the Greek island of Chios. Fruit wounds influenced oviposition behaviour in three ways. First, females were more likely to land on oranges (Citrus sinensis) that were artificially wounded than into unwounded control oranges. Second, having landed, females were more likely to attempt oviposition into a wounded orange than into control oranges. Third, females that attempted oviposition into wounded oranges usually did so directly into or very near the wound. The diameter and depth of the wound significantly influenced the tendency for female flies to land on a fruit but not their propensity, having landed, to attempt oviposition in or near the wound. The significance of this behavior in nature and implications for management of the Mediterranean fruit fly are discussed.

---

Résumé Des observations fortuites nous ont suggéré que C. capitata Weidemann utilise les blessures des fruits, y compris d'anciennes piqûres de ponte, pour déposer ses oeufs. Ce comportement a été quantifié dans une orangeraie de l'île grecque de Chios. Les blessures des fruits influent sur la ponte de 3 façons. D'abord, les femelles atterissent plus fréquemment sur les oranges, Citrus sinensis, artificiellement blessées que sur les fruits intacts. Ensuite, après atterrissage, les femelles tentent plus souvent de pondre sur une orange blessée que sur des oranges intactes. Enfin, les femelles pondent directement dans la blessure ou à proximité. Le diamètre et la profondeur de la blessure influent sur la tendance à l'atterrissage, mais non sur les tentatives de ponte dans la blessure ou près d'elle. La signification de ce comportement dans la nature et ses conséquences sur la lutte contre C. capitata sont discutées.

     

Oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens

We assessed the role of visual and olfactory cues on oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae). In a field survey, we evaluated the stage of susceptibility of field‐grown tomatoes by monitoring N. cyanescens infestations from fruit‐setting up to harvest, in relation to post‐flowering time, size, and visual properties of fruit. In two‐choice laboratory experiments, we tested the degree to which females use visual and olfactory cues to select their host plant for oviposition. In addition, we investigated the ability of flies to avoid fruit already infested by conspecific eggs or larvae, and the influence of natal host fruit on oviposition preference. Neoceratitis cyanescens females preferentially lay their eggs in small yellow‐green unripe fruit (2–3.5 cm diameter, 10–21 days post‐flowering). Damage to fruit was significantly affected by brightness and size properties. In laboratory experiments, females chose to lay their eggs in bright orange rather than yellow domes. On the sole basis of olfactory stimuli, females showed a significant preference for unripe vs. ripe host fruit, for unripe fruit vs. flowers or leaves, and for host vs. non‐host fruit (or control). However, colour interacted with odour as females dispatched their eggs equally between the yellow dome and the bright orange dome when unripe fruit of tomato was placed under the yellow dome vs. ripe fruit under the bright orange dome. When offered real ripe and unripe tomatoes, females preferred unripe tomatoes. Females significantly chose to lay eggs in non‐infested fruit when they were given the choice between these or fruit infested with larvae. In contrast, recent stings containing eggs did not deter females from laying eggs. Rather, they could have an attractive effect when deposited within <1 h. Regardless of their natal host plant, tomato or bugweed, N. cyanescens females laid significantly more eggs in a dome containing bugweed fruit. However, 15% of females originating from tomato laid eggs exclusively in the dome with tomato, against 3% of females originating from bugweed.     

Incidence of apple fruit and leaf surface metabolites on Cydia pomonella oviposition

Water soluble metabolites identified from surfaces of apple tree fruit and leaf stimulate oviposition in Cydia pomonella L. The effects of two artificial blends of primary metabolites representing fruit and leaf surfaces, respectively, and of components within the blends were examined on egg-laying after two time periods: 3 min and 25 min of darkness. An artificial mixture of six metabolites, viz., three sugar alcohols (sorbitol, quebrachitol, and myo-inositol) and three sugars (glucose, fructose, and sucrose) did stimulate egg-laying. Fructose, sorbitol, and myo-inositol are important components of the stimulatory blend. Contact durations may induce variations in egg-laying responses. After 3 min of darkness, there were no differences in numbers of females laying eggs nor in the numbers of eggs laid on cloths treated with the complete blends and the controls. There were, however, clear effects of groups of compounds and of individual compounds. Reduced blends without sugars and sugar alcohols were in many cases significantly less stimulatory than the complete blends and the controls. After 25 min of darkness, the proportions of females laying eggs as well as the numbers of eggs were higher after treatment with the complete blends than on the controls. The proportions of females laying eggs on cloths treated with the reduced blends were rather similar to the controls, whereas there were still significant effects on the numbers of eggs laid after treatment with reduced blends derived from fruits but not from leaves.     

Is fruit size important in the selection of oviposition sites by cranberry fruitworm,Acrobasis vaccinii?

Under laboratory conditions, females of Acrobasis vaccinii (Riley) (Lepidoptera: Pyralidae) oviposit significantly more often on larger than on smaller cranberry fruit. This behaviour ensures that neonate larvae have access to maximum resources and are larger when moving to the next fruit. However, while there is some evidence that on a large spatial scale females may lay eggs in patches of larger fruit, there was no evidence of such an oviposition preference within patches in natural bogs. These results may be explained by the fact that the oviposition period for A. vaccinii begins early in the cranberry season, before fructification is completed, leading to potential competition among females for the first fruit present in the environment. Laying eggs on the first fruit available may be advantageous as this behaviour increases the probability that females select unexploited fruit. This strategy would be particularly effective for maximizing female fitness in grazer frugivorous species (such as the cranberry fruitworm) that live in environments where severe climatic conditions induce limited flowering/fruit formation and where hosts thus are rare.     

Prior experience influences the fruit residence of male apple maggot flies,Rhagoletis pomonella

Male apple maggot flies spend considerable time residing on individual host fruit as territories on which they force-copulate arriving females in search of oviposition sites. Here, we present evidence from investigations in nature and the laboratory that shows the propensity of males to reside on a hawthorn or apple fruit as a territory is significantly modifiable through prior experience with fruit and, hence, involves learning. Previous studies revealed that after a female apple maggot fly, Rhagoletis pomonella, arrived on a host hawthorn or apple fruit, its propensity to accept or reject that fruit for egg-laying was similarly modifiable through prior fruit-exposure experience and also involved learning. We discuss how host fruit learning in males and females, in concert with genetic-based differences in host fruit residence and acceptance behavior between populations of flies originating from hawthorn and apple, could give rise to a reduction in gene flow between populations of flies on these two host types.     

Oviposition preferences in Grapholita molesta: the relative importance of visual and olfactory cues

The oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), is a major pest of fruit trees worldwide. Females oviposit on the young leaves of peach [Prunus persica (L.) Batsch (Rosaceae)] shoots at twilight, when light intensity changes markedly. Previous researches have shown that the oviposition response of this moth is guided particularly by visual and olfactory cues from host plants. However, the relative importance of visual and olfactory cues in their oviposition preference is largely unknown. As a crepuscular moth, how do choices change as light intensity drops rapidly from day to night? In the present study, through two‐choice behavioural experiments, the oviposition responses of G. molesta to visual and olfactory cues (alone or in combination) from peach shoots were tested at four light intensities ranging from daylight to starlight. Grapholita molesta showed similar oviposition responses to plant cues under 1 000, 100, 1 and 0.01 mW m^?2 illumination. Olfactory cues from peach shoots attracted significantly more oviposition than the negative control, whereas visual cues alone did not. Furthermore, olfactory cues were more attractive than visual cues, and no significant interaction was observed between the responses to the two cues. Our findings indicate that G. molesta females mainly rely on olfactory cues to recognize oviposition sites, regardless of differences in light intensity. These results do not provide evidence for attraction to visual cues, but the possibility that the brightness of leaves might be used to guide oviposition is discussed.     

An investigation into the reproductive characteristics ofMicroctonus hyperodae (Hym.: braconidae), a parasitoid ofListronotus bonariensis (Col.: Curculionidae)

The reproductive tract of the parasitoidMicroctonus hyperodae was found to comprise 6.1±0.2 ovarioles containing a total of 40–60 oöcytes. After oviposition into its hostListronotus bonariensis, the parasitoid's egg volume increased by 205 times prior to hatching. At 19.1°C ovipositingM. hyperodae survived for a mean 21±4 days and laid a mean of 48±8 eggs.M. hyperodae collected from Colonia, Uruguay laid a mean of 62±15 eggs which was significantly more than the other ecotypes. Under caging conditions with an ample supply of hosts,M. hyperodae laid 51% of its eggs in the first 72 hours and on average 41% of the species' life-span occurred after the exhaustion of its egg supply. Minimum temperature forM. hyperodae oviposition was found to be c. 5°C; beyond this the rate of increase in egg-laying was approximately linear until 30°C whereafter the rate fell abruptly. There was effectively no egg-laying at 39°C. The parasitoid showed no preference for one host sex or the other either in the laboratory or under field conditions. Compared to otherMicroctonus spp.,M. hyperodae appeared to show low fecundity and high longevity. The adaptive implications of this are discussed.