Feeding behaviour of Epilachna vigintioctopunctata (Coleoptera: Coccinellidae) on Luffa aegyptiaca

Observations on adult Epilachna vigintioctopunctata Fabr. on Luffa aegyptiaca show that these insects prefer flowers in light and leaves and flowers in dark. Probably physical and chemical stimuli, originating from the flowers, guide beetles to them in light. In darkness the insects' comparatively greater preference to leaves and flowers suggests that the attractants and arrestants present in both these parts of the plant are mainly in the form of chemical stimuli bearing equal intensity. These insects prefer to feed on the corolla of the flower of L. aegyptiaca. This preference is affected by stimulants in these parts of the plant. The nature and characteristics of these stimuli are unknown.

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Comportement alimentaire d'Epilachna vigintioctopunctata (Coleoptera, coccinellidae) sur Luffa aegyptiaca

Résumé Cette étude expose les résultats d'observations sur l'orientation et sur le préférendum alimentaire de la coccinelle Epilachna vigintioctopunctata Fabr. à l'égard des diverses parties de sa plante hôte: Luffa aegyptiaca. Les expériences réalisées sont décrites et les données numériques obtenues ont été soumises au calcul statistique. Il a été établi que dans des conditions d'obscurité les insectes se portent en nombre presque égal sur les fleurs et sur les feuilles, alors qu'à la lumière, les fleurs sont nettement plus attractives. En ce qui concerne leur alimentation, les insectes préfèrent se nourrir aux dépens de la corolle de la fleur.Les divers facteurs, chimiques ou visuels, pouvant intervenir dans l'orientation de l'insecte et dans son comportement alimentaire, sont discutés.

     

Life table and predatory efficiency of Stethorus gilvifrons (Coleoptera: Coccinellidae), an important predator of the red spider mite, Oligonychus coffeae (Acari: Tetranychidae), infesting tea

The ladybird beetle, Stethorus gilvifrons, is a major predator of the red spider mite, Oligonychus coffeae, infesting tea. Biology, life table and predatory efficiency of S. gilvifrons were studied under laboratory conditions. Its average developmental period from egg to adult emergence was 19.2 days. After a mean pre-oviposition period of 5.3 days, each female laid an average of 149.3 eggs. Adult females lived for 117.3 days and males for 41.5 days. The life table of the beetle was characterized by an intrinsic rate of increase (r) of 0.066 day⁻¹, net reproductive rate (R ₀) of 72.2 eggs/female, gross reproduction rate (Σm _x ) of 82.3 eggs/female, generation time (T) of 64.9 days, doubling time of 10.5 days and finite rate of increase (λ) of 1.07 day⁻¹. Population dynamics of S. gilvifrons and its prey, O. coffeae, was monitored by sampling 25 tea leaves from each experimental block grown under the prevailing field conditions. Populations of S. gilvifrons reached a peak during January to March and had low incidence during June to November. Peaks in the populations of S. gilvifrons coincided with the abundance of O. coffeae in tea fields. Weather factors such as low temperature, high humidity and heavy rainfall adversely affected the populations of S. gilvifrons. The predatory efficiency of S. gilvifrons increased during the growth of larval instars. An adult female consumed 205.0 eggs, 92.2 larvae, 81.8 nymphs and 52.4 adult mites per day.     

Attraction of the predator,Harmonia axyridis (Coleoptera: Coccinellidae), to its prey,Myzus persicae (Hemiptera: Aphididae), feeding on Chinese cabbage

The predatory multicolored Asian lady beetle, Harmonia axyridis, was attracted to volatiles released from Chinese cabbage infested by the green peach aphid, Myzus persicae, in T-tube olfactometer choice tests. However, lady beetle adults and larvae did not respond to clean air, Chinese cabbage alone or green peach aphid alone. Of different prey densities, H. axyridis adults were most attracted to Chinese cabbage infested by 60 M. persicae adults after 24 h. However, H. axyridis larvae were not attracted to Chinese cabbage infested by M. persicae. Mechanically damaged Chinese cabbage attracted neither lady beetle adults nor larvae. Predatory adults were attracted to 60 M. persicae adults after 24 and 48 h, and to 90 M. persicae adults after 12 h, suggesting that the predatory response depends on the prey density. Lady adult beetles did not prefer the volatiles induced by Diamondback moth, Plutella xylostella, indicating that specific host insect specificity attracts respective natural enemies. It can be explained that the volatile compounds emitted from the host plant as a result of herbivore attack preferred by the specific insect species.     

Effect of temperature on the development and consumption of Phaenochilus kashaya (Coleoptera: Coccinellidae), a predator of the cycad aulacaspis scale,Aulacaspis yasumatsui

The cycad aulacaspis scale (CAS), Aulacaspis yasumatsui Takagi (Hemiptera: Diaspididae), is a serious pest of ornamental cycads in the southeastern United States. In Florida, CAS was first reported in Miami in 1996 and is now present in 43 Florida counties. Chemical control of CAS can be effective, but it is expensive, and insecticides must be frequently and regularly applied. Recent surveys of natural enemies in Thailand identified a new potential biological control agent of CAS. The objective of this study was to examine the temperature requirements and consumption rates of Phaenochilus kashaya Giorgi and Vandenberg (Coleoptera: Coccinellidae). Survival, developmental time and number of scales consumed by P. kashaya were measured at four constant temperatures (20, 25, 30 and 35°C). In addition, adult longevity and consumption were recorded at three constant temperatures (20, 25 and 30°C). Phaenochilus kashaya completed development to adulthood at temperatures ranging from 20 to 30°C. The highest survival rate (48%) was obtained at 25°C, and the accumulated degree-days for this species was 714. Phaenochilus kashaya is a voracious predator of CAS, consuming 380 scales during the larval stage and an estimated 4700 scales during the adult stage. Adult longevity varied from 59 days at 30°C to 220 days at 20°C for females, and 31 days at 30°C to 148 days at 20°C for males. The intrinsic rate of increase (r _m) was 0.34 at 20°C, which is high compared with other coccinellid species. According to this study, P. kashaya has the potential to be an effective biological control agent of the CAS in Florida.     

The feeding behaviour of the rice leaf folder, Cnaphalocrocis medinalis

During feeding, the larva sits longitudinally on the leaf, bends the head sideways, and scrapes out the soft tissue between bundles longitudinally up and down, leaving only the bundle unit + bundle sheath, sclerenchyma, and the abaxial epidermis + cuticle between the bundles intact, when feeding on the upper side. Feeding on the underside also includes most of the bulliform cells, sparing again the bundle unit plus the remaining adaxial epidermis cells + cuticle between the bundles. Feeding is essentially restricted to green mesophyll tissue and may occur practically over the whole leaf surface. Of the eaten portion of a leaf, about two-thirds is consumed (by dry weight). Regular longitudinal feeding was observed in many other species of Gramineae, and in several Cyperaceae. In a few cases of thick or tough leaves feeding ocurred also in irregular non-linear fashion. Extensive irregular feeding was also observed in one specimen of a soy plant. Young larvae up to the early second instar are gregarious, but subsequently become solitary, with only one larva per leaf roll.

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Zusammenfassung Während die Raupen fressen, sitzen sie in Längsrichtung auf dem Blatt, neigen den Kopf seitlich und scharren das weiche Gewebe zwischen den Leitbündeln aus. Unberührt bleibt beim Fressen von der Oberseite her nur das Leitbündel mit der Bündelscheide, das Sklerenchym, die abaxiale Epidermis mit der Kutikula. Beim Fressen auf den Unterseite wird auch der grösste Teil der Bulliformzellen erfasst. Dabei wird das Gefässbündel mit der nun adaxialen Epidermiszellen und der Kutikula zwischen den Bündeln ausgeschlossen. Das Fressen ist hauptsächlich auf das grüne Mesophyllgewebe beschränkt und kann praktisch über die ganze Blattoberfläche stattfinden. Ungefähr zwei Drittel des Trockengewichtes eines befressenen Blattabschnittes wird verzehrt. Regelmässiges Fressen in Längsrichtung wurde auch an vielen andern Gramineen- und Cyperaceenarten beobachtet. An einigen dicken und harten Blättern, z.B. Bambus, wurde manchmal in einer ganz unregelmässigen Weise gefressen. Solch unregelmässiges Fressen wurde auch einmal auf einer Soyapflanze beobachtet. Junge Raupen, sind bis zum frühen zweiten Stadium gregär, werden aber später solitär mit einer einzigen Raupe in einer Blattrolle.

     

Comparative 2-DE proteomic analysis of date palm (Phoenix dactylifera L.) somatic and zygotic embryos

Two-dimensional gel electrophoresis coupled to mass spectrometry has been used to compare the proteome of date palm (Phoenix dactylifera L. cv. Deglet Nour) zygotic and somatic embryos. Proteins were trichloroacetic acid–acetone–phenol extracted, quantified, and resolved by 2-DE in the 5 to 8 pH range. Total protein content and number of resolved spots were higher in zygotic (110 ± 14.5 mg/g DW; 349 spots) than in somatic (70.96 ± 4.8 mg/g DW; 210 spots) embryos. The 2-DE map of both systems showed qualitative (263) and quantitative (72) differences. Statistical analysis of spot intensity was performed by PCA, obtaining two accurate groupings of the samples and determining the most discriminating spots. Samples were also clustered using Euclidean distance with average linkage algorithm of the Genesis software package. Sixty-three variable spots were subjected to mass spectrometry analysis, resulting in 23 identifications. Identified proteins were classified in the following functional categories; glycolysis (8 proteins), citrate cycle (1), ATP synthesis (1), carbohydrate biosynthesis (2), amino acids metabolism (1), stress related (4), storage (3), and with no function assigned for three of them. Most of the somatic embryo specific proteins identified belonged to glycolysis pathways, whereas those of the zygotic embryo to storage and stress-related proteins. Differences are discussed in terms of metabolism and biology of both types of embryos.     

Life history of Axinoscymnus cardilobus (Col., Coccinellidae), a predator of Bemisia tabaci (Hom., Aleyrodidae)

Abstract:  Axinoscymnus cardilobus is an indigenous coccinellid predator in South China, which feeds on many whitefly species. Its development, consumption rate, survivorship, longevity and fecundity on a diet of eggs and nymphs of Bemisia tabaci were evaluated. Larval consumption decreased sharply as instars of B. tabaci become bigger, and development time of beetle larvae was significantly different when fed on different stages of B. tabaci . The sex ratio was 0.44. The performances were better after feeding on whitefly eggs than nymphs. Axinoscymnus cardilobus showed good potential for biological control of B. tabaci , especially in greenhouse situations.     

烟粉虱天敌日本刀角瓢虫的捕食行为

研究了日本刀角瓢虫雌成虫和幼虫捕食粉虱时的各种行为时间分配.结果表明,日本刀角瓢虫成虫的捕食行为可分为爬行、取食、清洁、静息、整翅和排泄6个部分.饥饿后的日本刀角瓢虫幼虫捕食烟粉虱卵时,幼虫各龄期间的取食和爬行时间无显著差异,对烟粉虱卵的处置时间随瓢虫幼虫虫龄的增大而缩短.日本刀角瓢虫雌成虫捕食烟粉虱卵时,饥饿后的雌成虫用于取食的时间显著长于非饥饿的雌成虫,而用于清洁、静息和爬行的时间显著短于非饥饿的雌成虫;饥饿后的瓢虫雌成虫对卵的处置时间显著长于非饥饿的雌成虫.饥饿后的日本刀角瓢虫雌成虫捕食烟粉虱若虫时,瓢虫雌成虫的取食时间随烟粉虱若虫虫龄的增大而增加,清洁和静息时间随烟粉虱若虫虫龄的增大而缩短,对若虫的处置时间随烟粉虱若虫虫龄的增大而增加.     

Foraging behaviour of Terek SandpipersXenus cinereus feeding on Sand-Bubbling CrabsScopimera globosa

Summary On the intertidal flats of the Nakdong Estuary in South Korea Terek Sandpipers foraged solitarily, and made 0.5–6 m long runs which ended with pecks on or into the sediment to capture Sand-bubbling Crabs. The birds foraged during low tide and spent about 80 % of their time foraging; the rest preening and resting. More than half of the recorded prey and over 80 % of the average energetic intake consisted of Sand-bubbling Crabs. As the size of captured crabs increased, a greater proportion was washed before ingestion. Small crabs were always swallowed, but of the larger crabs an increasing portion was eventually rejected after capture. When deep down in their burrows, only the smallest crabs were within the reach of the sandpipers' bills. Henceforth, the crabs were only available when outside their burrows, on the surface. This happened for only three hrs (or one third) of each diurnal low tide period. Early in the tidal cycle after the crabs came to the surface, Terek Sandpipers made many runs and pecks per unit time to capture them. When crabs were most abundant and easy to catch, the birds were apparently more selective in their prey choice: more captured crabs were washed before being eaten and more were eventually rejected. Suggestions are made to explain the behaviour of both the predator and the prey.

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Verhalten von Terekwasserläufern(Xenus cinereus) beim Erbeuten von Winkerkrabben(Scopimera globosa)

Zusammenfassung Im Watt der Nakdong-Mündung in Südkorea gingen Terekwasserläufer einzeln der Nahrungssuche nach; ihre Beute waren hauptsächlich Winkerkrabben. Nach einer Laufstrecke von 0.5–6 m pickten sie nach der Beute auf oder im Sediment. Die Vögel suchten während des Niedrigwassers nach Nahrung und verwendeten dafür etwa 80 % ihrer Zeit; den Rest verbrachten sie mit Putzen und Rasten. Mehr als die Hälfte der festgestellten Beute und über 80 % der mittleren Energieaufnahme bestand ausScopimera globosa. Mit steigender Beutegröße wurde ein größerer Anteil der Beute vor dem Verschlucken gewaschen. Kleine Krabben wurden immer verschluckt, während von den größeren ein zunehmender Anteil schließlich verworfen wurde. Wenn die Krabben tief unten in ihren Höhlen saßen, befanden sich nur die kleinsten in der Reichweite der Schnäbel. Daher waren die meisten Krabben nur außerhalb ihrer Höhlen an der Oberfläche erreichbar, und zwar lediglich während drei Stunden (oder einem Drittel) der täglichen Niedrigwasserperiode. Früh in der Tidenperiode, wenn die Krabben an die Erdoberfläche gekommen waren, liefen und pickten die Terekwasserläufer pro Zeiteinheit oft, um die Krabben zu fangen. Wenn die Krabben am häufigsten waren und sich am leichtesten fangen ließen, waren die Vögel anscheinend selektiver in ihrer Beuteauswahl: Mehr Krabben wurden vor dem Verzehr gewaschen und mehr wurden schließlich verworfen. Zur Erklärung des Verhaltens sowohl des Räubers als auch der Beute werden Hypothesen angeboten.

     

Defensive behaviour of the wheat aphid,Schizaphis graminum (Rondani) (Hemiptera: Aphididae), against Coccinellidae

An account is given of the behaviour of the wheat aphid, Schizaphis graminum, in response to attacks by two coccinellid predators Scymnus morelleti and Exochomus concavus. Various responses are described and their influence on predator efficiency is investigated.     

Studies of the behaviour of Artioposhia triangulata (Platyhelminthes; Tricladida), a predator of earthworms

A significant negative correlation between the numbers of earthworms and the flatworm was demonstrated in fromalin-sampled lawns. Their distributions, recorded by a transect from a shrub border where the flatworm is suspected to have been introduced, indicated that predation may lead to earthworm extinction. Two different vermarium designs demonstrated a gradation of earthworm vulmerability to the flatworm due to depth within the soil and burrow width rather than perference for specific earthworm species. A strong correlation between the level of earth worm predation and flatworm movement implied active hunting. A predation rate was found to be 0.67 of an earthworm per flatworm per week with a metabolic conversion rate of 10%.     

The effect of photoperiod on Coccinella transversoguttata (Coleoptera: Coccinellidae)

Diapause in Coccinella transversoguttata can be inhibited by exposing adult females to photoperiod regimens of LD 16 : 8 or 14 : 10 hours. The photoperiod regimen to which the immature instars are exposed has little effect on the diapause status of the adult female.

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Résumé Coccinella transversoguttata est un des plus importants prédateurs des Pucerons de la pomme de terre dans l'État du Maine (U.S.A.). C'est la photopériode à laquelle les adultes sont soumis qui conditionne la diapause imaginale de cet insecte: une photopériode jour/nuit de 16 : 8 heures empêche la diapause, alors qu'une photopériode jour/nuit de 12 : 12 heures déclenche la diapause. Un éclairement permanent n'a pas d'effet significatif sur l'inhibition de la diapause. La photopériode à laquelle sont soumis les ufs, les larves et les nymphes n'a guère d'effet sur la diapause des adultes. La photopériode n'a pas non plus d'influence sur le développement larvaire ni sur la mortalité des larves ou des adultes.

     

The role of the maxillary and labial palps in the feeding behaviour of Schistocerca gregaria

The role of the maxillary and labial palps in the initiation and maintenance of feeding has been analysed in female fifth-instar nymphs of Schistocerca gregaria. The ability to perceive single chemicals prior to feeding and to feed to repletion on them is markedly reduced in the absence of the palps. Increasing the sensory input of suboptimal diets by providing an attractive odour results in an increased meal length in insects without palps but not in controls.Insects without their palps reared on a diet of lettuce and bran eat relatively less bran and more lettuce than do the controls, although the total volume of food ingested is the same. The smaller dry weight of food consumed as a result of this greater lettuce intake results in a significantly smaller dry weight gain over the fifth instar.

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Zusammenfassung Bei Fünftlarven von Schistocerca gregaria wurde analysiert, welche Rolle die Maxillar- und Labialpalpen beim Frassbeginn und während des Fressens spielen. Palpenlose Insekten nahmen einzelne Chemikalien vor dem Fressen weniger wahr und frassen auch weniger als Kontrolltiere. Die sensorische Qualität suboptimalen Futters konnte durch einen attraktiven Geruch verbessert werden, was zu verlängerter Fresszeit bei palpenlosen Insekten, nicht aber bei Kontrolltieren, führte.Palpenlose Insekten, die auf einer Diät von Salat und Kleie gehalten wurden, frassen weniger Kleie und mehr Salat als Kontrolltiere, wobei das Volumen der aufgenommenen Nahrung gleich blieb. Durch den erhöhten Salatkonsum wurde die Trockensubstanzmenge der aufgenommenen Nahrung vermindert. Als Folge davon nahmen die Tiere während des fünften Larvenstadiums gesichert weniger an Trockensubstanz zu als Kontrolltiere.

     

Prey stage preference and feeding behaviour ofOligota kashmirica benefica (Coleoptera: Staphylinidae), an insect predator of the spider miteTetranychus urticae (Acari: Tetranychidae)

We studied the prey stage preference and feeding behaviour of the first to third instar larvae and adult females ofOligota kashmirica benefica Naomi (Coleoptera: Staphylinidae), a predator of the spider miteTetranychus urticae Koch (red form) (Acari: Tetranychidae), on leaves of the kudzu vine (Pueraria lobata (Wild.) Ohwi (Leguminosae)) under laboratory conditions. The number of mites eaten increased with the growth of predator larvae. Third instar larvae preyed on all stages of spider mite, whereas first instar larvae preyed mainly on immobile stages (eggs and quiescent stages). The predator larvae showed two types of foraging behaviour (active searching and ambush behaviour) when targeting the mobile stages (larval nymph and adult stages of prey). Although no difference was found in the number of prey consumed by adult females and third instar larvae of the predator, the adult females mainly attacked and consumed the immobile stages.     

The effect of ozone fumigation and different Brassica rapa lines on the feeding behaviour of Pieris brassicae larvae

Elevated levels of tropospheric ozone and their effects on plants have been studied for a great number of years. Ozone is a gaseous pollutant and acts as a phytotoxin. Even though ozone is known to change the physiology of plants, little attention has been given to the indirect effects of ozone on plant-insect interactions. This paper addresses this question by investigating the interactive effects of ozone and plant genotype on insects. Lines of rapid-cycling Brassica rapa (L.) selected for their contrasting sensitivity to ozone and Pieris brassicae (L.) (Lepidoptera: Pieridae) were used as a model system. The effect of differences in ozone sensitivity and ozone fumigation on the plant's carbon and nitrogen pools, the feeding preference, and behaviour of P. brassicae larvae were investigated. The results show that the plant's susceptibility to ozone interacts in a complex way with ozone induced alterations in the suitability of the plant for the insect. Only the larval performance on the sensitive line was affected by ozone exposure. Biochemical changes in the resistant B. rapa line made the plant a better food source for the insects, since the digestibility of this plant was significantly higher than that of the sensitive line, and the larvae pupated more quickly and were heavier.     

Amblyseius bibens (Acarina: Phytoseiidae), a predator of spider mites (Tetranychidae) in Madagascar

Field observation indicated thatA. bibens is an important predator of severalTetranychus-species in parts of Madagascar. Its dependence on water for drinking was demonstrated; this feature limits its presence to more humid biotopes. Its importance in the irrigated areas of the dry southwest is stressed.A. bibens proved capable of eradicating.T. urticae on potted bean plants. Predation and oviposition of the predator were tested with various densities of adult femaleT. urticae. At the lowest densities tested, predation was limited by the availability of the prey, which also resulted in a lower oviposition rate at these densities. At more moderate densities (of around 32 prey/7 cm²) an increase in prey egg consumption made up for a decrease in adult prey consumption, indicating that spider mite eggs are suitable food for this predator. At high densities eggs were ignored and adult prey were killed and at highest densities more were killed than were actually needed for food. The effect of alternate feeding on eggs and an interference stimulation component are claimed to explain the unusual functional response curve ofA. bibens. The results imply that, under natural conditions,A. bibens feeds primarily on spider mite eggs, but shifts towards adult prey consumption with increasing prey densities.

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Résumé Des observations dans la nature montrent queA. bibens est un important prédateur de plusieurs espèces deTetranychidae dans certains secteurs à Madagascar. Son importance dans les zones irriguées du sud-ouest aride est mise en évidence, ce qui résulte des besoins pour cette espèce d'eau alimentaire, ce facteur limitant sa présence aux biotopes les plus humides. A. bibens se montre capable d'éliminerT. urticae sur les cultures de pois. Le taux de prédation et d'oviposition du prédateur ont été testés en rapport aux diverses densités de la proie,T. urticae. Aux densités les plus faibles la prédation est limitée par la disponibilité en proies, ce qui entraine également une réduction de la fécondité. Pour des densités moyennes (de l'ordre de 32 proies/7 cm²) on observe une consommation préférentielle des ufs deTetranychidae et une moindre consommation des adultes. Pour des densités élevées, par contre, les ufs sont délaissés et ce sont les adultes qui sont consommés, enfin par des densités encore plus fortes, le prédateur détruit plus de proies adultes qu'il n'en peut consommer.L'effet d'une, alimentation de substitution sur les ufs de la proie et l'interférence d'un facteur stimulant sont envisagés comme éléments explicatifs de la réponse inhabituelle d'A. bibens. Cela implique que dans les conditions naturellesA. bibens se nourrit en premier lieu sur les ufs deTetranychidae, mais transfert sa préférence sur les proies adultes quand la densité de ces derniers s'accroît.

     

Rafting behaviour and predator disturbance to Steller's EidersPolysticta stelleri in northern Norway

Steller's Eiders responded to overflying Great Black-backed GullsLarus marinus by spooking — flushing from feeding and aggregating on open water. Birds did not react at high tide when aggregated into dense roosting flocks. The significant reduction in inter-bird distance associated with this escape behaviour suggests that rafting in this way (and at rest) serves an anti-predator function. In 32% of spooks, up to 56% of the flocks were displaced from feeding sites; even when all birds remained, they took an average of 3.5 minutes for half of the flock to resume feeding, representing a minimum total of 17% loss of feeding time throughout the 24 hour period. At observed rates, the cost of flight behaviour in response to gulls was estimated to equate to a minimum of 7.8% of daily existence energy. Hence such predator responses can cost Steller's Eiders loss of access to favoured feeding area, loss of feeding time (already restricted by tidal exposure) and additional energy costs.

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Zusammenfassung Auf überfliegende Mantelmöwen reagieren Scheckenten, in dem sie überstürzt von ihren Nahrungsplätzen auffliegen und sich auf dem offenen Wasser zusammenscharen. Wenn sich die Enten bei Flut zu dichten Ruhegesellschaften zusammengeschlossen haben, ist keine Reaktion zu beobachten. Die Reduktion der Individualabstände in Verbindung mit Fluchtverhalten deutet darauf hin, daß der enge Zusammenschluß eine Reaktion gegen Räuber bedeutet. In 32% der Fluchtbewegungen entfernten sich bis zu 56% der Trupps von den Stellen der Nahrungssuche. Aber auch, wenn die Vögel am Ort bleiben, dauerte es im Mittel 3,5 min, bis die Hälfte der Trupps die Nahrungssuche wieder aufgenommen hatte. Dabei gingen innerhalb von 24 Stunden immerhin 17% der Zeit für Nahrungssuche verloren. Die Kosten für das überstürzte Abfliegen beim Auftauchen von Möwen wird auf etwa 7,8% des täglichen Mindestenergiebedarfs geschätzt. Daher kann eine derartige Raktion auf potentielle Räuber die Nutzung bevorzugter Nahrungsgründe einschränken sowie Verlust der ohnehin durch die Gezeiten beschränkte Zeit für Nahrungsaufnahme und zusätzliche Energiekosten nach sich ziehen.

     

Effects of temperature on development, survival, longevity, and fecundity of the Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) predator, Axinoscymnus cardilobus (Coleoptera: Coccinellidae)

Axinoscymnus cardilobus (Homoptera: Aleyrodidae) is an important predator of Bemisia tabaci (Coleoptera: Coccinellidae) that occurs in high population density of B. tabaci. Temperature among other factors is observed to play an important role in the development of arthropods. The effect of temperature on the development of A. cardilobus was studied at seven constant temperature regimes (14, 17, 20, 23, 26, 29, 32 °C). The results indicated that the duration of egg, larval and pupal stages were significantly influenced by increased temperature. The rate of development gradually increased with increase in temperature from 14 °C to 26 °C, but declined from 26 °C to 32 °C. The survival rates of different insect stages were stable at temperatures between 20 °C and 26 °C, but at extreme temperatures of 32 °C and 14 °C, a sharp decrease was evident. Ovipositional period of the female decreased when temperatures were increased from 17 °C to 32 °C. The highest fecundity of the female (225.7 eggs per female) was recorded at 23 °C. Life tables of A. cardilobus were constructed based on the experimental results at temperatures of 14–32 °C. The reproductive rate (R₀), the innate capacity for increase (r_m) and the finite rate of increase (λ) reached the maximum values at 23 °C, of 70.7, 0.059 and 1.062, respectively. The mean generation time (T) decreased with increased temperature from 17 °C to 32 °C, the highest and least values recorded at 17 °C and 32 °C were 112.7 and 38.7, respectively. These results offer valuable insight on the importation and establishment of A. cardilobus into new environments with diverse temperature regimes.     

Prey stage preference and feeding behaviour of Oligota kashmirica benefica (Coleoptera: Staphylinidae), an insect predator of the spider mite Tetranychus urticae (Acari: Tetranychidae)

We studied the prey stage preference and feeding behaviour of the first to third instar larvae and adult females of Oligota kashmirica benefica Naomi (Coleoptera: Staphylinidae), a predator of the spider mite Tetranychus urticae Koch (red form) (Acari: Tetranychidae), on leaves of the kudzu vine (Pueraria lobata (Wild.) Ohwi (Leguminosae)) under laboratory conditions. The number of mites eaten increased with the growth of predator larvae. Third instar larvae preyed on all stages of spider mite, whereas first instar larvae preyed mainly on immobile stages (eggs and quiescent stages). The predator larvae showed two types of foraging behaviour (active searching and ambush behaviour) when targeting the mobile stages (larval, nymph and adult stages of prey). Although no difference was found in the number of prey consumed by adult females and third instar larvae of the predator, the adult females mainly attacked and consumed the immobile stages.     

Adult survival of Delphastus catalinae (Coleoptera: Coccinellidae), a predator of whiteflies (Hemiptera: Aleyrodidae), on diets of whiteflies, honeydew, and honey

Delphastus catalinae (Horn) is a coccinellid predator that is commercially sold for the management of whiteflies. A study was conducted to assay the effect of selected diets on the survival of adult D. catalinae. Treatments of water (as a control), 10% honey, honeydew, and whiteflies [Bemisia tabaci (Gennadius)] were provided to the beetles in laboratory assays. Newly emerged, unfed adult insects were used at the start of a survival experiment with trials lasting 50 d. Another survival experiment used mixed-aged adults from a greenhouse colony, and the trials lasted 21 d. Survival was poor on a diet of solely water; ~1% survived beyond a week at 26°C. Survival using the newly emerged insects was similar between those fed honeydew and honey diets, but those on the whitefly diet had the greatest survival (~60% on day 50). However, in the experiment with mixed-aged beetles, adults on honey, and whitefly diets performed the same over a 21-d experiment. Excluding those on the water diet, survival of beetles on the various diets ranged from ~50-80% after 21 d. In an open choice assay across 7 h, D. catalinae adults were found on the whitefly diet in a much greater incidence than on the other diets, and the number of beetles found on the whitefly diet increased over time. The data supports that when D. catalinae are employed in greenhouses or fields for whitefly management, during low prey populations, honeydew from the whitefly can help sustain the population of this predator. Moreover, a supplemental food such as a honey solution can help sustain the population of D. catalinae when the prey is decreased to low numbers. These results may help in the development of strategies to enhance the utility of predators for the management of whiteflies.