Orientation behaviour of the predatory hemipteran Perillus bioculatus to plant and prey odours

The pentatomid predator P. bioculatus responded by positive odour-conditioned anemotaxis when exposed to airborne volatiles emitted by potato plants damaged by Colorado potato beetle larvae, whereas intact potato plants and non-feeding larvae as odour sources failed to elicit anemotaxis. Walking tracks of adult predators had higher values of straightness and upwind fixation when odours emanating from mechanically damaged plants were encountered than tracks registered in response to air carrying volatiles from intact plants, but these parameters returned to control values within 1–2 h after damage was caused. In contrast, air led over plants damaged by beetle larvae elicited orientation responses at least 3 hours after feeding damage ceased. The combination of chemical data on headspace composition, olfactory sensitivity established in electro-antennogram studies and behavioural data presented here imply a role of sesquiterpenoid plant volatiles as odorous cues eliciting attraction of this predator to damaged potato plants.     

Functional Response ofColeomegilla maculata(Coleoptera: Coccinellidae) to Colorado Potato Beetle Eggs (Coleoptera: Chrysomelidae)

A comparative study of the functional response ofColeomegilla maculataDeGeer (Coleoptera: Coccinellidae) fourth instars was conducted under laboratory, greenhouse, and field conditions. In the laboratory, individual larvae were placed in 9-cm petri dishes for 24 h, with 1, 3, 5, or 7 Colorado potato beetle (Leptinotarsa decemlineata[Say]) (Coleoptera: Chrysomelidae) egg masses. Each egg mass was standardized at 15 eggs. In the greenhouse and field,C. maculatalarvae were provided with an equivalent of 0.5 to 35L. decemlineataegg masses/m²of potato leaf. Fourth instars ofC. maculataexhibited a type II functional response toL. decemlineataeggs under laboratory, greenhouse, and field conditions. Predator search efficiency was inversely related with prey density. The maximum mean attack rate (8.7 eggs) byC. maculatalarvae in the field was about half the mean attack rate in the laboratory (17.6 eggs) and greenhouse (20.1 eggs). The difference in prey density between the laboratory and field seems to have been a major contributing factor in determining the rate of predation, whereas differences in environmental conditions (e.g., temperature and possible alternate food) may explain the differences observed in the predation rate in the greenhouse and field.     

Olfactory response of three parasitoid species (Hymenoptera: Braconidae) to volatiles of guavas infested or not with fruit fly larvae (Diptera: Tephritidae)

The olfactory responses of the native parasitoids Doryctobracon areolatus (Szépligeti) and Asobara anastrephae (Muesebeck) and of the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) to guava (Psidium guajava L.) infested or not with fruit fly larvae were evaluated. D. areolatus and D. longicaudata females responded to the odors of uninfested rotting guavas, although D. areolatus was also attracted to fruits at the initial maturation (turning) stage. The females of these species recognized the volatiles of guavas containing Ceratitis capitata (Wied.) larvae. However, in bioassays involving fruits with larvae of different instars, D. longicaudata females were not able to separate between fruits containing C. capitata larvae at the initial instars and larvae at the third instar. In the evaluations of volatiles released by guavas containing C. capitata and Anastrepha fraterculus (Wied.) larvae, the D. longicaudata females were oriented toward the volatiles of fruits containing both host species, but differed significantly from volatiles of guavas containing C. capitata larvae. The D. areolatus females also showed responses to both species, although with a preference for volatiles of fruits containing A. fraterculus larvae. The A. anastrephae females were oriented toward the odors of fruits infested with both fruit fly species. In the shade house, D. longicaudata females were oriented to volatiles of rotting fruits containing larvae or not, but could not significantly differentiate between hosts. D. areolatus females were not attracted toward fruits on the ground in the shade house, regardless of host, suggesting that this parasitoid does not forage on fallen fruits.     

Does superparasitism improve host suitability for parasitoid development? A case study in the Microplitis rufiventris-Spodoptera littoralis system

Superparasitism refers to the oviposition behavior of parasitoid females who lay their eggs in an already parasitized host. Recent studies have shown that allocation of additional eggs to an already parasitized host may be beneficial under certain conditions. In the present work, mortality of Microplitis rufiventris wasps was significantly influenced by both host instar of Spodoptera littoralis larvae at parasitism and level of parasitism. In single parasitization, all host instars (first through sixth) were not equally suitable. Percentage of emergence success of wasp larvae was very high in parasitized first through third (highly suitable hosts), fell to 60% in the fourth instar (moderate suitable) and sharply decreased in the penultimate (5th) instars (marginally suitable). Singly parasitized sixth (last) instar hosts produced no wasp larvae (entirely unsuitable), pupated and eclosed to apparently normal adult moths. The scenario was different under superparasitism, whereas supernumerary individuals in the highly suitable hosts were almost always killed as first instars, superparasitization in unsuitable hosts (4th through 6th) had significant increase in number of emergence success of wasp larvae. Also, significantly greater number of parasitoid larvae successfully developed in unsuitable hosts containing three wasp eggs than counterparts containing two wasp eggs. Moreover, the development of surplus wasp larvae was siblicidal in earlier instars and nonsiblicidal gregarious one in the penultimate and last “sixth” instars. It is suggested that the optimal way for M. rufiventris to deal with high quality hosts (early instars) is to lay a single egg, while the optimal way to deal with low quality hosts (late instars) might be to superparasitize these hosts.     

Olfactory responses ofTrichogramma maidis Pint,et Voeg.: Effects of chemical cues and behavioral plasticity

Oriented responses of Trichogramma maidisPint, et Voeg. to airborne odors were observed in a four-armed olfactometer. Experiments were carried out with odors of host eggs, the sex pheromone of Ostrinia nubilalisHbn, and maize extract, offered singly or in combination, both to naive wasps and to wasps previously exposed to the tested odor during an oviposition experience. The exploratory behavior in the olfactometer was quantified by means of a computer program which performed a space-time analysis of the insect 's movements. Whereas the naive wasps did not respond to the odor of the eggs, the synthetic sex pheromone of O. nubilalis,or the maize extract presented singly, they did react to a mixture of these three volatile cues. Prior oviposition in the odor of maize extract or in the combination of odors induced an increased preference toward the conditioning scent. This phenomenon did not occur when the wasps were conditioned to egg odor or sex pheromone alone. These results suggest that females can learn to associate some olfactory cues with the presence of the host. Immediately following the presentation of the combination of odors, a strong attraction of experienced wasps occurred; it decreased as the experiment progressed and finally reached the level presented by naive insects. Adult conditioning to the combination of odors also resulted in reduced variability in the behavioral responses.     

Population dynamics of the potato tuber moth on processing tomatoes in Israel

The potato tuber moth (PTM),Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), is a major pest of processing tomatoes,Lycopersicon esculentum Mill. (Solanaceae), in Israel. The larvae penetrate the tomato fruit through the stem end and present a serious threat to crop quality. Foliage and fruit samples were taken in nine commercial tomato fields located in Israel's three main tomato growing areas, two of which are potato growing areas as well. PTM was not found where potatoes were absent. Potato harvest in nearby fields was found to be the most significant factor affecting seasonal trends in PTM population density in tomatoes. All four larval instars were found in foliage on all sampling dates. Significantly higher proportions of first instars were found during the population density increase which followed potato harvest. Damaged fruits did not contain first instar larvae, indicating that PTM never undergoes complete development within tomato fruit. Fruit damage levels at harvest were positively correlated to the peak mean population densities on foliage and the date they were observed. In tomato fields not adjacent to potatoes, infestation was first observed at the edge of the field. Both before and after the potato harvest in nearby fields, population density at the edge of the field was significantly higher than at the center. In tomato fields adjacent to potatoes, no significant differences were found between population densities at the edge and center before the potatoes were harvested. After the potato harvest, population density at the center of tomato fields was higher than at the edge. Deceased, October 1988     

Deterrent effects of larval tracks on conspecific larvae in <Emphasis Type="Italic">Cycloneda limbifer</Emphasis>

The response of Cycloneda limbifer Say (Coleoptera: Coccinellidae) larvae to conspecific larval tracks was investigated with the assistance of the automatic video tracking system EthoVision. Single larvae were monitored for 1 h in an arena with a choice of two substrates, one clean and one contaminated with the tracks of conspecific larvae. Fourth instar larvae of C. limbifer effectively differentiated clean substrates from substrates with fresh tracks of conspecific first instars. Larvae walked significantly further on clean than on contaminated substrates in each 20-min period of the 1 h trials. With the exception of the first 20-min period, residence times were also longer on clean than on contaminated substrates. The mean velocity of larvae on the substrates did not differ in any period of the test. The results indicate that a deterring pheromone in fresh tracks of C. limbifer larvae effectively deters conspecific larvae from staying on sites previously exposed to larvae. The mode of action of the semiochemical repellent secreted by larvae is complementary to a previously described semiochemical-mediated egg-spacing mechanism in the coccinellid C. limbifer. Active distribution of larvae has the potential to improve the initial distribution of offspring by females among aphid colonies of varying qualities and may facilitate survival during changes in the distribution of conspecific larvae in the course of the development.     

Influence of adult experience on host microhabitat location by the generalist parasitoid,Campoletis sonorensis (Hymenoptera: Ichneumonidae)

The effect of adult experience on microhabitat location behavior of the generalist parasitoid Campoletis sonorensis (Cameron)was examined in a wind tunnel bioassay. Responses were tested to the odors of two host plants (cotton and sesame) of Heliothis virescens (F.) or a nonhost plant (potato), either damaged and infested with host larvae and host products (host/plant complex) or intact, clean and uninfested. Parasitoid females remained naive or were allowed one oviposition experience on either of the plants, 1 min, 2 h, or 24 h prior their introduction into the wind tunnel. In a no-choice test, parasitoids experienced 1 min prior to bioassay completed significantly more flights to sesame and potato host/plant complexes than did naive parasitoids. However, 24 h after experience, only females experienced on potato completed more flights to the host/ plant complex than did naive females. Parasitoids experienced 1 min prior to flight to undamaged plants showed a slight increase in flight response (significant only for potato) but, after 24 h, completed only as many flights as naive parasitoids. In a dual-choice situation, parasitoids did not show a preference for either of the two host plants but did prefer a host to a nonhost plant. This innate plant preference was not changed by a single oviposition experience. The potential significance of these results to the microhabitat location behavior of C. sonorensisin the field is discussed.     

Effects of stone topography on abundance of net-building caddisfly larvae and arthropod diversity in an upland stream

We investigated whether small pits on the surfaces of stream stones affected abundances of net-spinning, hydropsychid larvae (Trichoptera) and species diversity in the Acheron River, southeastern Australia. On stream stones, nets occurred more often in small (at least 5 mm width) pits than expected by chance. However, proportionately high numbers of pits were not associated with high abundances of either of two species of hydropsychid larvae (both Asmicridea spp). A colonization experiment, using bricks with 0, 4, 12 or 30 small (diam. 5.5 mm) and large (13 mm) pits drilled into the top surfaces, showed that numbers of nets were related to numbers of pits. Small pits were preferred over large ones and the pits, as a group, were occupied almost entirely by late instars of both species. However, only Asmicridea sp. 1 was more abundant on pitted bricks; Asmicridea sp. 2 showed no response. The differences between the species, and between the stone and brick results, can be explained by different proportions of late instars in the samples. Many I instars probably did not make nets. Hence, higher numbers of larvae on pitted surfaces is expected only when late instars are relatively frequent, as was true for Asmicridea sp. 1 on bricks. There were no effects of pits per se or increased numbers of hydropsychid nets on species diversity or the abundances of other common species. These results contrast with those of other studies, which found stone topography or hydropsychid nets to increase species diversity on stones.     

Ontogenetic shifts in the functional response and interference interactions of Rhyacophila dorsalis larvae (Trichoptera)

1. Ontogenetic shifts in predator behaviour can affect the assessment of food‐web structure and the development of predator–prey models. Therefore, it is important to establish if the functional response and interference interactions differ between life‐stages. These hypotheses were tested by (i) comparing the functional response of second, third, fourth and fifth larval instars of Rhyacophila dorsalis, using three stream tanks with one Rhyacophila larva per tank and one of 10 prey densities between 20 and 200 larvae of Chironomus sp.; (ii) using other experiments to assess interference within instars (two to five larvae of the same instar per tank), and between pairs of different instars (one, two or three larvae per instar; total predator densities of two, four or six larvae per tank). 2. The first hypothesis was supported. The number of prey eaten by each instar increased with prey density, the relationship being described by a type II model. The curvilinear response was stronger for fourth and fifth instars than for second and third instars. Mean handling time did not change significantly with prey density, and increased with decreasing instar number from 169 s for fifth instars to 200 s for second instars. Attack rate decreased progressively with decreasing instar number. Handling time varied considerably for each predator–prey encounter, but was normally distributed for each predator instar. Variations in attack rate and handling time were related to differences in activity between instars, fourth and fifth instars being more active and aggressive than second and third instars, and having a higher food intake. 3. The second hypothesis was partially supported. In the interference experiments between larvae of the same instar or different instars, mean handling time did not change significantly with increasing predator density, and attack rate did not change for second and third instars but decreased curvilinearly for fourth and fifth instars. Interference between some instars could not be studied because insufficient second instars were available at the same time as fourth and fifth instars, and most third instars were eaten by fourth and fifth instars in the experiments. Prey capture always decreased with decreasing attack rate. Therefore, interference reduced prey consumption in fourth and fifth instars, but not in second and third instars. The varying feeding responses of different instars should be taken into account when assessing their role in predator–prey relationships in the field.     

Nocturnal Calling Behavior in Mantids

Females of Mantis religiosa and Empusa pennata were video taped for several 24 h periods to determine if they showed behaviors associated with pheromone release. In the photophase the abdomen of both species was motionless and rested in continuous contact with the wings. However, at the beginning of the scotophase the females bent the abdomen ventrally so that the space between the abdomen and the wings increased significantly with respect to the daytime posture. Calling behavior (abdominal bending) was maintained throughout the 8 h scotophase and ended abruptly at lights on. Females of M. religiosa did not start calling until they were 30 days of age. Calling disappeared in mated females, but it reappeared two weeks later. Males stayed motionless in response to the odors emitted by other males or by noncalling females, but walked when a calling female was placed in the air flow. These observations suggest that female mantids bend their abdomens at night to release a sex pheromone. The adaptive function of nocturnal sex pheromone release in sexually cannibalistic species that rely strongly on visual cues for mating is discussed.     

Sources of variation in rapidly inducible responses to leaf damage in the mountain birch-insect herbivore system

Summary Studies on rapidly inducible resistance in trees against insect herbivores show substantial variation in the strength of responses. Here we report the results of a study which examined causes of this variation. We bioassayed the quality of leaves of two developmental phases (young vs. mature) of the mountain birch Betula pubescens ssp. tortuosa by measuring the growth of two instars of Epirrita autumnata larvae. We used only short shoot leaves from trees of a natural stand, uniform in size and age. Damage was caused by larvae and artificial tearing of leaf lamina, varying the scale and time. We separated seasonal changes in plants from instar-dependent effects of the animals by testing experimental larvae in two subsequent growth trials. We found that only larval-made damage induced responses in leaves that made the leaves significantly poorer quality for the test larvae. Artificial damage induced only weak responses, and artificial canopy-wide damage even caused slight improvement of leaf quality. Cumulative leaf damage did not strengthen birch responses. Leaves that were in the expansion phase responded to damage while fully-expanded, mature leaves showed no response. The pattern of responses indicated that there might be physiological constraints: small-scale damage induced resistance against the larvae but largescale damage did not. Prevalent weather conditions might have modified these responses. Larvae of two instars and sexes, of low- and high-density populations responded to leaf damage similarly. However, prior experience of larvae with the host plant may have affected subsequent larval performance. Variation in rapidly inducible responses in birches was caused by plant characters rather than by test animals.     

Selection of healthy and nuclear polyhedrosis virus infectedAnticarsia gemmatalis [Lep.: Noctuidae] as prey by nymphalNabis roseipennis [Hemiptera: Nabidae] in laboratory and on soybean

Nabis roseipennis Reuter nymphs demonstrated a preference for nuclear polyhedrosis virus (NPV) — infected over healthyAnticarsia gemmatalis Hübner larvae when offered a choice of larval prey in Petri dishes and on soybean. In Petri dishes, small (second-third instar) and large (fifth-sixth instar) nymphs attacked a significantly greater number of diseased than healthy larvae at all larval instars tested (first-fifth instars) and exposure periods (2, 5 and 24 h), except that at 2 h the number of 1^st and 3^rd instar larvae attacked by large nymphs did not differ significantly (P≤0.05). Nabis roseipennis caged with larvae on individual soybean plants in the greenhouse resulted in a generally low percentage of attack by small and large nymphs after 2 days, ranging from 5.6 to 36.7%. As in the Petri dishes, the nabids showed a significant preference for diseased larvae over healthy larvae attacked for all nabid and larval sizes on soybean, with the percentage of diseased larvae attacked ranging from 28.0 to 65.4% (P≤0.05). This preference for diseased larvae on soybean as well as in Petri dishes demonstrates that the preference was not due to the close proximity in which the host and prey were found in the Petri dishes. The preference for diseased larvae may be due to a reduction in a defensive response in late stages of disease. This material is based upon work supported in part by USDA Grant No. 83-CRCR-1-1212.     

Mate recognition inCryptomyzus aphids: copulation and insemination

The acceptability of three widely distributed Australian Menispermaceae,Tinospora smilacina Benth.,Sarcopetalum harveyanum F. Muell. andStephania japonica (Thunb.) Miers, as food for larvae of the fruitpiercing moth,Othreis fullonia (Clerck), was examined in three laboratory experiments. When larvae were presented with plant species individually total development times were shortest onT. smilacina and longest onS. japonica, despite relatively similar consumption rates within most instars.T. smilacina elicited greater (P<0.05) relative growth rates thanS. japonica in all instars except the 6th. In the second experiment, when larvae were allowed to select from each of the 3 plants, noS. japonica was chosen by 1 st instars and it represented only 3.7% of food consumed by 2nd instars. Significantly moreT. smilacina was eaten in each instar thanS. japonica, and more thanS. harveyanum except in the 2nd and 4th instars. The final experiment examined the abilities of larvae to switch hosts when forced after the 1st and 3rd instars. After the first or second food change largest average headcapsule widths were associated with feeding onT. smilacina as the most recent food. Feeding by final instars onT. smilacina also resulted in the shortest development time and highest puparial weights. While some larvae survived irrespective of plant sequence 83.3% of the recorded mortality occurred while larvae were exposed toS. japonica, principally during the 1st instar. These experiments lend support to field observations which suggest thatT. smilacina is a major host ofO. fullonia whileS. japonica is notS. harveyanum is probably an important alternate host whenT. smilacina is scarce.     

大豆蚜嗅觉在选择寄主植物中的作用

大豆蚜ＡＰｈｉｓｇｌｙｃｉｎｅｓ有翅和无规孤雌生殖蚜为其寄主植物大豆叶和鼠李叶气味所引诱,而非奇主植物棉花叶和黄瓜叶气味处于中性,丝瓜叶和南瓜叶气味具有明显的排斥作用。非寄主植物气味可以遮蔽寄主植物气味的引诱作用。大豆蚜触角感受器对植物气味具有嗅觉生理反应,对一些化合物的最小感觉阈值达１０－５至１０－６体积比浓度,表明大豆蚜触角上存在识别植物气味的嗅觉受体细胞。由此证明,嗅觉在大豆蚜选择寄主植物过程中起重要作用。     

Prey-related odor preference of the predatory mites Typhlodromalus manihoti and Typhlodromalus aripo (Acari: Phytoseiidae)

Typhlodromalus manihoti and Typhlodromalus aripo are exotic predators of the cassava green mite Mononychellus tanajoa in Africa. In an earlier paper, we showed that the two predators were attracted to odors from M. tanajoa-infested cassava leaves. In addition to the key prey species, M. tanajoa, two alternative prey mite species, Oligonychus ossypii and Tetranychus urticae also occur in the cassava agroecosystem. Here, we used a Y-tube olfactometer to determine the attraction of the predators to odors from O. gossypii- or T. urticae-infested cassava leaves and their prey-related odor preference. T. aripo but not T. manihoti was slightly attracted to odors from O. gossypii-infested leaves. Both predator species showed a stronger response to odors from cassava leaves infested by M. tanajoa over odors from cassava leaves infested by O. gossypii. Neither predator species was attracted to odors from T. urticae-infested leaves and the predators preferred the odors from M. tanajoa-infested leaves over those from T. urticae-infested leaves. When O. gossypii was present together with M. tanajoa on the same leaves or on different sets of leaves offered together as an odor source the two predators were attracted. In contrast, after mixing non-attractive odors from T. urticae-infested leaves with attractive odors from M. tanajoa-infested leaves, neither T. aripo nor T. manihoti was attracted. Ecological advantages and disadvantages of the predators’ behavior and possible implications for biological control of M. tanajoa are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Oviposition and feeding preferences of a flower-feeding weevil,Coelocephalapion aculeatum, in relation to conspecific damage to its host-plant

The oviposition and feeding preferences ofCoelocephalapion aculeatum Fall (Coleoptera: Apionidae), a host specific florivore ofMimosa pigra L. (Mimosaceae), were studied in relation to conspecific damage to its hostplant. Adults ofC. aculeatum cease ovipositing in inflorescences when the egg load reaches a number consistent with the larval carrying capacity of the inflorescence. The basis for this oviposition deterrence was examined by offering inflorescences damaged by adult feeding alone, larval feeding alone and a combination of adult feeding and oviposition. Adults preferred to oviposit on inflorescences which are not damaged by either adult feeding, larval feeding, or oviposition. No evidence for the existence of an oviposition deterring pheromone (ODP) was found. I suggest that the ability of a single host inflorescence to support the development of many larvae causes selection for the use of these oviposition deterring cues which can convey more quantitative information about the level of previous infestation than can ODPs. Adults fed a similar amount on damaged compared to undamaged inflorescences. These results assisted in the design of host range testing trials and allows predictions to be made about the effectiveness of this insect as a biological control agent.     

Effect of CryIC toxin from Bacillus thuringiensis on larval feeding behavior of Spodoptera exigua

The lack of data on the effect of Bacillus thuringiensis (B.t.) toxins on larval feeding behavior of the pest Spodoptera exigua (Hübner) (Noctuidae: Amphypyrini) prompted us to investigate the effect of three delivery systems of CryIC, a commercial formulation, inclusion bodies, and the activated CryIC toxin. The commercial formulation was the least and CryIC toxin the most lethal form to neonates of susceptible colonies. All but two of the treatments in choice tests with neonates and third instars showed significant avoidance of B.t. treated diet, with greater proportion of larvae from susceptible (UCR-S and AUBURN-S) and resistant (AUBURN-R) colonies on untreated diet than on diet treated with any of the CryIC forms and concentrations tested. Furthermore, third instars consumed significantly more control than treated diet for all CryIC forms, colonies and concentrations. The avoidance of CryIC toxin by neonates and third instars strongly suggests that CryIC, which also is present in the commercial formulation and in the inclusion bodies, is responsible for eliciting avoidance behavior by S. exigua larvae. Behavioral observations of third instars in a no-choice test on either treated or control diet indicated that questing behavior in susceptible larvae appears to be positively related with presence of CryIC toxin in the diet. Furthermore, resistant third instars were on the whole more active than susceptible thirds on both treated and control diet. Resistant thirds raised on CryIC treated diet (AUBURN-RC) spent more time eating treated diet than resistant larvae raised on control diet (AUBURN-R), suggesting that diet conditioning plays an important role on feeding behavior of S. exigua. The implications of these results are discussed.     

植食性昆虫寄主植物嗅觉搜寻述介

植食性昆虫与寄主植物关系的本质是化学。植食性昆虫搜寻寄主的嗅觉媒介是植物气味即化学信息物质。在介绍植物气味构成及其扩散模型基础上,阐述了植物气味在地上植食性昆虫成虫、幼虫和地下植食性昆虫搜寻寄主过程中的嗅觉导向作用,并指出了今后相关研究需要注意的问题。从植物与环境因子的关系来看,植物气味包括构成性气味和诱发性气味两类,这两类气味的概念既相联系而又不同。构成性气味组分及构成因植物分类地位等而不同。诱发性气味组分因植食性昆虫取食、植物病原微生物、机械致伤等因子的胁迫而变化,这种变化性状随植物属和/或种、植株生长发育阶段、胁迫因子性质及其作用方式而不同。无论是哪种植物气味,其释放均具有节律性。气味扩散过程比较复杂,扩散状态可用数学模型表征。对于地上植食性昆虫成虫,植物气味对其寄主搜寻行为具有导向特异性,重点分析了这种特异性形成的两个假说;鳞翅目昆虫幼虫,能够利用植物化学信息物质趋向寄主植物或回避非寄主植物;地下植食性昆虫搜寻寄主,既与寄主植物地下组织释放或分泌的次级代谢物有关,又与一些初级代谢物有关。初级代谢物中的CO₂,起着“搜寻触发器”作用。有助于增强人们对昆虫与植...     

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.