Functional response of the ladybird, Cydonia vicina nilotica to cowpea aphid, Aphis craccivora in the laboratory

The functional response of Cydonia vicina nilotica Muls. （Coleoptera： Coccinellidae） to six densities of Aphis craccivora Koch （Homoptera： Aphididae） nymphs on broad bean （Viciafaba Linn.） was investigated in the laboratory. A linear relationship between the rate of consumption and prey density was observed with r^2 values between 0.58 and 0.97. Plotting prey density against prey killed by four larval instars, and adult males and females of C. vicina nilotica fit well with the type Ⅱ model of Holling＇ s disc equation. Adult females consumed the highest number of prey, followed by fourth instars and adult males. Based on the functional response data, the model predicts a maximum of 144.9, 116.3, 86.2, 80.0, 72.5 and 20.0 nymphs to be consumed per day by an individual adult female, fourth instar, adult male, third, second and first instars, respectively. The differences in the responses of the predator to aphid densities are discussed.     

BIOLOGY OF CHRYSOPA PHYLLOCHROMA WESMAEL （NEUROPTERA： CHRYSOPIDAE）. Ⅱ： INTRASPECIFIC INTERFERENCE AND SEARCHING CAPACITY

The present study examined intraspecific interference and searching behavior of Chrysopa phyllochroma Wesmael (Neuroptera: Chrysopidae) for Aphis gossypii Glover (Homoptera: Aphididae) nymphs under laboratory and greenhouse conditions. The results were shown as follow: 1) In four different arenas (i.e. Petri dish, glass vessel, glass vessel with barriers in it, and cage with potted cotton plant), the predaceous efficiency of C. phyllochroma larvae varied with the predator density, the hunt constant (Q) and the intraspecific interference (m)increased with the prey density but decreased with the space heterogeneity; 2) In cage with potted cotton plant, the first- and second-instar green lacewing larvae consumed 13.6 and 29.4 cotton aphids/day respectively. The number of cotton aphids consumed by C. phyllochroma on lower leaves was significantly less than that on upper leaves; and 3) In cage with potted cotton plant, the percentage of the first- and second-instar green lacewing larvae located on upper leaves was significant less than that on lower leaves.     

Food preference of the rove beetle, Atheta coriaria Kraatz （Coleoptera： Staphylinidae） under laboratory conditions

A study, involving laboratory choice tests, was conducted to determine the feeding behavior, based on food preference, of the adult and larval stage of the rove beetle, Atheta coriaria Kraatz when presented with both fresh moistened oatmeal and second instar fungus gnat, Bradysia sp. nr. coprophila （Lintner） larvae in Petri dishes. Rove beetles used in this study came from a laboratory-reared colony. A rating scale from 1 to 5, based on percent missing （1 = 0 to 10%, 2 = 11 to 30%, 3 = 31 to 50%, 4 = 51 to 75%, and 5 = 76 to 100%）, was used to objectively assess the amount of oatmeal and number of fungus gnat larvae consumed by each rove beetle adult and larva. In all the choice tests, A. coriaria adults and larvae preferred to feed on fungus gnat larvae （78% and 69%, respectively） significantly more so than oatmeal （9% and 5%, respectively） based on the amount of oatmeal and number of fungus gnat larvae consumed after 4 and 6 hours. There were relatively minimal differences in the amount of food consumed for both adults and larvae after 4 and 6 hours. The results of this study indicate that oatmeal may be an inexpensive supplemental food source, during the rearing process, which will not inhibit the effectiveness of rove beetles to control fungus gnat larvae when released into greenhouses.     

Is Tetranychus urticae suitable prey for development and reproduction of nafve Coleomegilla maculata？

The lady beetle Coleomegilla maculata De Geer is an omnivorous predator that could help suppress aphid and spider mite populations on plants in greenhouses, plantscapes or interiorscapes. We are assessing the nutritional requirements and feeding behavior of C. maculata on target prey （spider mites） and factitious （unnatural） food. Our ultimate goal is to develop an efficacious diet to mass produce C. maculata. In this study, we tested the hypothesis that Tetranychus urticae Koch （two-spotted spider mite） is not suitable prey for development and reproduction of naive C. maculata （i.e., with no prior exposure to T. urticae）. Our objectives were to （i） provide baseline data on the effects of consuming T. urticae on C. maculata life history, （ii） to compare the effects of consuming all stages of T. urticae versus eggs ofMusca domestica L. （common housefly）, and （iii） to determine if the consumption of plant products was beneficial. We used C. maculata from a colony reared only on Ephestia kuehniella Zeller （Mediterranean flour moth） eggs. In experiments, C. maculata larvae were reared from the first instar to adult stage with prey/food in replicated arenas; adult females were paired with a single male with prey/food. The results showed that naive C. maculata readily attacked and consumed T. urticae. Nevertheless, T. urticae was less suitable than M. domestica eggs for C. maculata development and reproduction. Applying a synthetic pollen-Chlorella alga powder （SPCA） in arenas containing T. urticae appeared to boost C. maculata female development and reproduction.     

Spatial distribution of banana skipper （Erionota thrax L.） （Lepidoptera： Hesperiidae） and its parasitoids in a Cavendish banana plantation, Penang, Malaysia

Spatial distribution of immatures of the banana skipper （Erionota thrax L.） and their parasitisms from three major parasitoids were studied in a Cavendish banana plantation from April 2004 to December 2004. Infestation levels and parasitism of E. thrax life stages were recorded from bunched plants （BP）, flowering plants （FP）, preflowered plants （PF）, broad leaf followers （BLF） and narrow leaf followers （NLF）, as well as on well managed and poorly managed plants. Mean numbers of the immatures and numbers parasitized from the nine blocks in the plantation were fitted to four dispersion indices. Significant numbers of E. thrax immatures and those parasitized by Ooencyrtus erionotae, Cotesia erionotae and Brachymeria albotibialis were recorded from BLF and PF; no eggs were found on BP and FP. Although infestation was higher on well managed plants, only larval parasitism was significantly different. Three of the four indices indicated that eggs and larvae were random while all the indices showed pupae to be clumped. Parasitized eggs and pupae were clumped （4/4 indices） while 3/4 indices revealed a random pattern for parasitized larvae.     

Can an Invasive Prey Species Induce Morphological and Behavioral Changes in an Endemic Predator？ Evidence from a South Korean Snake （Oocatochus rufodorsatus）

Introduction of an invasive prey species into an ecosystem may affect an endemic predator＇s fitness by altering the prey-predator system. Successful adaptation may allow the endemic predator to eat and control the invasive species, while unsuccessful adaptation may result in extinction of the predator. We examine the possible effects of the invasive North American bullfrog （Rana [Lithobates] catesbeiana） on the endemic Red-backed rat snake （Oocatochus rufodorsatus） in South Korea. We do so by comparing the morphology and behavior of adult and hatchling snakes from bullfrog-exposed （Taean） and bullfrog-unexposed （Hongcheon） populations. Among the seven morphological characteristics investigated, relative tail length （tail length/snout-vent length） of both adults and hatchlings from Taean was significantly greater than that of adults and hatchlings from Hongcheon. Also, adult snakes from Taean had a signiifcantly shorter latency of ifrst tongue lfick in response to prey compared to adults from Hongcheon. This difference was not observed in hatchlings. In other snake species, a longer relative tail length and shorter latency of ifrst tongue lfick are known to improve foraging efifciency, and these characters may be adaptations ofO. rufodorsatus to prey on bullfrogs. This study provides preliminary evidence that the presence of an invasive prey species may cause morphological and behavioral changes in an endemic predator.     

Evaluations of larvicidal activity of medicinal plant extracts to Aedes aegypti （Diptera： Culicidae） and other effects on a non target fish

A preliminary study was conducted to investigate the effects of the extracts of 112 medicinal plant species, collected from the southern part of Thailand, on Aedes aegypti. Studies on larvicidal properties of plant extracts against the fourth instar larvae revealed that extracts of 14 species showed evidence of larvicidal activity. Eight out of the 14 plant species showed 100% mosquito larvae mortality. The LC50 values were less than 100μg/mL （4.1μg/ mL-89.4μg/mL）. Six plant species were comparatively more effective against the fourth instar larvae at very low concentrations. These extracts demonstrated no or very low toxicity to guppy fish （Poecilia reticulata）, which was selected to represent most common non-target organism found in habitats ofAe. aegypti, at concentrations active to mosquito larvae. Three medicinal plants with promising larvicidal activity, having LC50 and LC50 values being 4.1 and 16.4 μg/mL for Mammea siamensis, 20.2 and 34.7 μg/mL forAnethum graveolens and 67.4 and 110.3μg/mL forAnnona muricata, respectively, were used to study the impact of the extracts on the life cycle ofAe. aegypti. These plants affected pupal and adult mortality and also affected the reproductive potential of surviving adults by reducing the number of eggs laid and the percentage of egg hatchability. When each larval stage was treated with successive extracts at the LC50 value, the first instar larvae were found to be very susceptible to A. muricata and the second instar larvae were found to be susceptible to A. graveolens, while the third and fourth instar larvae were found to be susceptible to M. siamensis. These extracts delayed larval development and inhibited adult emergence and had no adverse effects on P. reticulata at LC50 and LC50 values, except for the M. siamensis extract at its LC50 value.     

Influence of light and habitat on predation of Culex quinquefasciatus （Diptera： Culicidae）larvae by the waterbugs （Hemiptera： Heteroptera）

The influence of light and habitat structure on the predation of Culex quinquefasciatus larvae by the common heteropteran water bug, Diplonychus （= Sphaerodema） annulatus, D. rusticus and Anisops bouvieri was assessed in the laboratory. It was revealed that water bugs predate more in presence of light than in dark conditions. While A. bouvieri consumed more prey in structured conditions, D. annulatus and D. rusticus consumed more prey in open conditions. The selection of prey size as well as the respective numbers varied between predators and treatments significantly. Prey vulnerability （PV）, an indicator of predatory efficiency, was highest for D. annulatus, moderate for D. rusticus and low for A. bouvieri. Prey consumption and PV values under different treatment conditions indicate that for belostomatid water bugs D. annulatus and D. rusticus, the order of prey consumption under different habitat and light/dark combinations is light open 〉 dark open 〉 light vegetated 〉 dark vegetated. In the case of the backswimmer, A. bouvieri, the order of prey consumption appeared to be light structured 〉 dark structured 〉 light open 〉 dark open. These findings were consistent with resource-partitioning by water bug species sharing the same guild. If the observed results are extended to natural settings the efficiency of these predators in controlling mosquito populations will vary with the structural complexity of habitats and the intensity of light.     

Development and immature survival of two aphidophagous ladybirds, Coelophora biplagiata and Micraspis discolor

The developmental parameters, namely developmental periods, larval survival, adult emergence, growth index, developmental rate and sex ratio in terms of female proportion in a population of two aphidophagous ladybirds, namely, Coelophora biplagiata （Swartz） and Micraspis discolor （Fabricius） were investigated, using three aphid species as prey. The immature stages of C. biplagiata were significantly affected by prey quality and developed fastest when fed on Aphis craccivora followed by Aphis gossypii and Rhopalosiphum maidis. The order of prey suitability in terms of developmental rate of immature stages of M. discolor was just reversed. The adult females were heavier than males, while pre-pupae were heavier than pupae in both ladybirds. The sex ratio of adult emergence, though female-biased in both ladybird species, was not significantly affected by prey quality.     

Oviposition behavior of the mirid Macrolophus pygmaeus under risk of intraguild predation and cannibalism

Zoophytophagous mirid species,that feed and develop either on prey or plant resources,are often found simultaneously on the same host.Hence,these species can engage in both intraguild predation and cannibalism,which can pose a threat to mirid eggs.Ovipositing females may respond to such risks of predation on their eggs by reducing the number of eggs laid or selecting safer oviposition sites.We tested the oviposition behavior of Macrolophus pygmaeus(Rambur)(Hemiptera:Miridae)females under the risk of cannibalism by M.pygmaeus males and intraguild predation by Nesidiocoris tenuis(Reuter)males(Hemiptera:Miridae)under laboratory conditions.Intraguild predators and cannibals were introduced during or after the oviposition period.The number of eggs laid(using counts of newly hatched nymphs)and their proportion on each part of a tomato plant were both measured.The results reveal that only cannibalism by M.pygmaeus males after the period of oviposition significantly decreased the number of hatched eggs.Cannibalism thus represents a greater risk to mirid eggs than intraguild predation.The M.pygmaeus female responded to the presence of potential intraguild predators(or competitors)by decreasing the nu mber of eggs laid in the upper leaves.The results suggest that M.pygmaeus females avoid competition by N.tenuis,by laying fewer eggs on upper leaves.Cannibalism could regulate zoophytophagous predator populations under prey scarcity conditions and minimize the risk of crop damage associated with those biological control agents.     

Relationship between predation by Podisus nigrispinus and developmental phase and density of its prey,Plutella xylostella

This study evaluated the predation by Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) at various densities of larvae and pupae of the pest Plutella xylostella (L.) (Lepidoptera: Plutellidae). We tested predator behavior of female P. nigrispinus at six experimental densities (1, 5, 10, 15, 20, or 25 prey items in a 1‐l transparent plastic container, replicated 15 times for each density) of both the fourth instar and pupae of P. xylostella. The number of prey consumed was monitored every 15 min for 12 h and was subsequently monitored at 24 h. Podisus nigrispinus females were weighed before and after the experiments to determine the effect of different densities of prey on their weight gain. Female predators had a Type‐II functional response, with attack rate estimated at 1.387 and 0.260 and a handling time of 0.091 and 0.183 h^?1 for larvae and pupae, respectively. Podisus nigrispinus consumed on average 10.9 larvae or 5.5 pupae in 24 h. Despite the similarity of the response type, P. nigrispinus preferred to feed on larvae, rather than on pupae.     

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.     

Functional response of Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) to Bemisia tabaci (Gennadius) on tomato leaves

Bemisia tabaci (Gennadius) is an important invasive pest of vegetables and other horticultural plants worldwide. In this study, the functional response of Neoseiulus cucumeris (Oudemans) to different stages of immature B. tabaci was evaluated under laboratory conditions. Predation experiments were conducted on tomato leaf discs (2.5?cm diameter) over a 24-h period at 26?±?1°C and 65?±?5% relative humidity with a L16:D8 photoperiod. The prey densities ranged from 5 to 90 immature stages (eggs and first- to fourth-instar nymphs) of B. tabaci per leaf disc. The results showed that the egg stage of B. tabaci was the most susceptible prey stage and that the mated female adult mite (3-day-old) was a more effective predator than the male adult mite. The functional response of adult N. cucumeris followed a Type II trend curve as shown in a logistic regression model. Adult N. cucumeris exhibited different predation tendencies towards prey in different stages of immaturity. The daily maximum number of eggs, first-, second- and third-instar nymphs of B. tabaci killed by a single female over a 24-h period (26?±?1°C, 65?±?5% RH and L16:D8 photoperiod) were 8.5, 5.2, 3.0 and 2.1, respectively, whereas the number killed by a single male was 6.0, 4.0, 2.3 and 1.8, respectively. The results of this study could help determine an effective B. tabaci biocontrol measure that employs a natural predator.     

Factors affecting detectability of prey DNA in the gut contents of invertebrate predators: a polymerase chain reaction-based method

This study aimed to determine factors that influence the detection of DNA of Plutella xylostella L. (Lepidoptera: Plutellidae) in the gut contents of arthropod predators when the polymerase chain reaction is used to amplify a diagnostic fragment of the gene coding for cytochrome oxidase subunit I. The effects of temperature, time since feeding, subsequent food intake, sex, weight, and species of predator on prey detectability were studied in the laboratory. Three types of predator were studied: the spider Venator spenceri Hogg. (Araneae: Lycosidae), a bug with sucking mouthparts, Nabis kinbergii (Reuter) (Heteroptera: Nabidae), and a coccinellid with chewing mouthparts, Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae). In all experiments, the detectability of prey DNA was negatively correlated with time post‐feeding. The duration of detectability differed among the predator species. The time calculated for median detection success at 20 °C ranged from 49.6 h in V. spenceri to 36.1 h in N. kinbergii and 17.1 h in H. variegata. In H. variegata, but not in V. spenceri, the rate of detection decreased with increasing temperature. Subsequent food intake did not affect the detectability of DNA of P. xylostella in V. spenceri. In H. variegata, sex and weight of the predator did not influence detection of prey DNA. In addition, this study uncovered potential sources of error caused by detection of prey DNA following secondary cannibalistic and intraguild predation. The results provide essential information for the interpretation of prey detection data from field‐collected predators’ gut contents.     

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.     

Impact of temperature and prey density on the predacious capacity and behaviour of Stethorus punctillum Weise

Temperature had various effects on the predacious efficacy of immature and mature stages of the coccinellid predator, Stethorus punctillum on the two-spotted spider mite, Tetranychus urticae. In the case of immature stages, food consumption at the lowest tested temperature (15°C) was significantly higher than that at higher temperatures (25 and 35°C). On the contrary, positive correlation between food consumption and temperature was evaluated in the case of adult predator. Regarding predator responses to different prey density, a high positive correlation between food consumption and prey density was evaluated among 4^th instar larvae of the predator, followed by adult predator, while younger instars did not show reasonable increases with increasing prey densities. These results confirm that larval and adult stages of S. punctillum exhibit “Type II” functional response. In conclusion, the 4^th instar larvae and adult predator are the most preferable stages in winter and summer crops to control T. urticae, respectively.     

Functional response of Neoseiulus californicus (Acari: Phytoseiidae) to Tetranychus urticae (Acari: Tetranychidae) on strawberry leaves

Neoseiulus californicus (McGregor) is a predatory mite employed for biological control of the agricultural pest Tetranychus urticae (Koch). We explored whether environmental differences, in this case the trichome densities of abaxial leaf surfaces of strawberry cultivars (‘Maehyang’ and ‘Sulhyang’ varieties) affect the functional response of adult female N. californicus preying on immature stages (egg, larva and nymph) of T. urticae. We also evaluated the functional response of N. californicus to eggs of T. urticae at different temperatures (15, 20, 25, 30 and 35°C). We conducted a logistic regression of the proportion of prey consumed as a function of initial prey density to identify functional response types, and used nonlinear least‐squares regression and the random predator equation to estimate attack rates and handling times. The functional response of adult female N. californicus to T. urticae was not influenced by non‐glandular trichomes on abaxial leaves but was affected by temperature. Overall, adult female N. californicus exhibited a type 2 functional response to T. urticae. The handling time of N. californicus was highest (1.9970 h) against T. urticae nymphs. The attack rate did not change much at 15–30°C, but was significantly higher at 35°C. The handling time decreased significantly with increasing temperature at 15–35°C. At 35°C, the attack rate was highest (0.2087) and the handling time was lowest (0.9511 h).     

Development and functional response of Coelophora inaequalis (Coleoptera: Coccinellidae) feeding on brown citrus aphid, Toxoptera citricida (Homoptera: Aphididae)

1 Development and survivorship of Coelophora inaequalis (F.) were evaluated in the laboratory on the brown citrus aphid, Toxoptera citricida (Kirkaldy) at 20 and 25 °C. Coelophora inaequalis could complete its life cycle feeding on T. citricida at these two temperatures. The developmental period from egg to adult was significantly longer at 20 °C (24.7 d) than at 25 °C (15.9 d). The survivorship of combined immature stages were higher at 25 °C (39.2%) than at 20 °C (34.3%). 2 The effects of prey densities (4–64 aphids per leaf disk) on the functional responses of C. inaequalis fourth‐instar larvae and female adults were investigated using grapefruit leaf disks over a 24‐h period at 25 °C and a photoperiod of LD 14 : 10 h. Logistic regression analyses indicated that fourth‐instar larvae and adults exhibited a type II functional response to aphid density. Fourth‐instar larvae had a higher search rate (0.1305) than C. inaequalis female adults (0.0989). The handling time of fourth‐instar larvae (30.4 min) was significantly longer than that of female adults (5.8 min). Collectively, C. inaequalis appears to be a promising biological control agent of T. citricida in the citrus groves.     

Life‐history parameters and predation capacity of Macrolophus pygmaeus and Nesidiocoris tenuis (Hemiptera: Miridae) on eggs of Plutella xylostella (Lepidoptera: Plutellidae)

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Biological studies ofDiadegma semiclausum (Hym., Ichneumonidae), a parasite of diamondback moth

Laboratory studies were conducted on certain aspects of biology ofDiadegma semiclausum Hellén, a larval parasite of a crucifer pest,Plutella xylostella (L.). Within the range of 15°C to 35°C, the higher temperature, the shorter was the duration of larval and adult stages. Egg hatching and adult emergence were high at 15°C to 30°C but were significantly reduced at 35°C. The higher the temperature, the higher was the proportion of males produced. Temperature threshold was 5.74°C for eggs, 3.80°C for larvae, 5.91°C for pupae and 6.60°C for adults.D. semiclausum oviposition in the first threeP. xylostella larval instars produced more parasite males than females but oviposition in the fourth instar produced significantly more females than males. Parasite adults tended to emerge from their pupae from 06∶00 to 09∶00 hours although some emerged at other hours during the photophase. Adult longevity and production of eggs increased when adults were provided with a food source (honey) compared with no food or provision of water alone. Parasite adults survived and laid eggs for 28 days when provided with food but for only three days when deprived of food.