Predation of the apefly,Spalgis epius (Lepidoptera: Lycaenidae) on citrus mealybug,Planococcus citri (Hemiptera: Pseudococcidae)

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae) is a serious pest of economically important crops worldwide. The apefly, Spalgis epius (Westwood) (Lepidoptera: Lycaenidae) is a potential predator of various species of mealybugs. Earlier investigation on its daily preying capacity and preference for prey stages on P. citri is incomplete. Hence, a study was conducted to find out the daily prey consumption ability and preference for prey stages by different larval instars of S. epius reared on P. citri in the laboratory. Through the 8-day developmental period with four larval instars, the daily prey consumption of S. epius increased from the first to the seventh day and decreased on the eighth day prior to the prepupal stage. Generally, there was a significant difference in the prey consumption on different days. When the prey stages were offered separately, the first to fourth instar larva of S. epius consumed, respectively, a mean of 199.6, 722.6, 1908.8, and 4625.6 eggs or 21.5, 77.0, 168.5, and 670.5 nymphs or 3.2, 7.2, 16.0, and 35.1 adults of P. citri. When an S. epius larva was fed on P. citri eggs, nymphs and adults separately, it consumed a mean of 7456.7 eggs, 937.6 nymphs, or 62.3 adults during its entire development. When the prey stages were offered all together, a single S. epius larva consumed 2618.4 eggs, 170.4 nymphs, and 39.7 adults of P. citri throughout its entire development. The study revealed that S. epius is a voracious predator of P. citri and thus could be utilized as a major biological control agent.     

A quantified ethogram for oviposition behavior and oviposition preference in the hemipterophagous butterfly Spalgis epius (Westwood) (Lepidoptera: Lycaenidae)

In this study, we examined the oviposition behavior and preference of Spalgis epius, a potential predator of mealybug crop pests. An ethogram of oviposition behavior was constructed based on observations made in an oviposition cage. Ovipositional behavioral acts were catalogued and separated into two behavioral repertoires: searching and egg laying. Gravid females of S. epius oviposited similar numbers of eggs on three mealybug species. Females preferred eggs and adults to nymphs of mealybugs for oviposition. Among three species of mealybugs attended by ants, females laid fewer eggs in the mealybug mass attended by Oecophylla smaragdina than on mealybugs attended by Tapinoma melanocephalum and Camponotus variegatus. Females preferred mealybug masses already containing conspecific eggs to mealybug masses containing conspecific larvae or Cryptolaemus montrouzieri larvae for egg deposition. Gravid females laid larger numbers of eggs under bright sunlight than in diffused sunlight or shade. The results of this study showed that S. epius can effectively attack any species of mealybugs, avoid intra- and interspecific competition, and co-exist with some species of ants attending mealybugs. With the knowledge of these behaviors, this predator can be effectively utilized as a major biological control agent of mealybugs.     

Population dynamics of Spalgis epius (Lepidoptera: Lycaenidae), a candidate biocontrol agent of mealybugs and its interaction with mealybug-attendant ants

Spalgis epius is an economically important hemipterophagous butterfly. Detailed information on the population dynamics, natural enemies, and prey range of S. epius and its association with mealybug-attendant ant species is lacking. Three years of field studies conducted at Bangalore University campus, Bengaluru, India on these aspects indicated that the population density of S. epius was greatest from June to December and least from February to May in the low land region. S. epius survived on eight prey species, which were present in different months, of which Phenacoccus indicus was recorded as a prey of S. epius for the first time. Different prey species occurred on 12 species of host plants. The occurrence of S. epius was negatively correlated with temperature and positively correlated with relative humidity and prey populations. Six mealybug-attendant ant species were associated with the larvae of S. epius. The seven general predators of S. epius adults were recorded. Knowledge on the population dynamics and a prey range of S. epius and its interaction with mealybug-attendant ant species could be helpful to using this predator as a major biocontrol agent of various species of mealybugs. This study contributed to our understanding of the population dynamics of a hemipterophagous butterfly.     

Analysis of the Territorial, Courtship and Coupling Behavior of the Hemipterophagous Butterfly, Spalgis epius (Westwood) (Lepidoptera: Lycaenidae)

In this study we examined the territorial, courtship and coupling behavior, mating interruptions and influence of sunlight on mating behavior in Spalgis epius (Westwood). We constructed an ethogram of territorial and courtship behavior, and catalogued the sequence of behavioral acts associated with mating behavior. Mating behavioral acts were divided into four repertoires i.e. pre-courtship, pre-coupling, coupling and post-coupling behaviors. Totally 22 behavioral acts were recorded from four repertoires. Tree canopy, canopy height and sunlight conditions are the important factors that influence copulation in S. epius. The courtship activity led to successful copulation in 71.9 % pairs. Incidence of different types of courtship and copula interruptions in S. epius was also recorded.     

Predation on eggs and larvae ofHeliothis virescens [Lep.: Noctuidae] by an adult predator complex in cage studies on cotton

Predation by a predator complex consisting of adults of the lygaeidGeocoris punctipes (Say), the nabidsNabis roseipennis Reuter and/orTropiconabis capsiformis Germar and the coccinelids,Hippodamia convergens Guerin-Meneville andColeomegilla maculata (DeGeer) onHeliothis virescens (F.) eggs, 1st-instar larvae or both on late pinhead square and early bloom stage cotton was evaluated in field cages in Mississippi. Prey densities of 4 (11, 512/ha) or 8 per cage and predator: prey (P:p) ratios of 1∶1, 2∶1, 3∶1, 4∶1 and 5∶1 were used. Prey were labeled with phosphorus-32 or carbon-14 to determine predator ingestion and effectiveness. Average percent egg predation as a function of P:p ratio ranged from 2.1 to 12.1 for a 48 h period. The average percent predation on larvae as a function of P:p ratio ranged from 5.3 to 22.0. The hemiptera fed more than the coleoptera on larvae, andG. punctipes was the best egg predator. For the range of predator densities used, the average area of discovery for the predator complex was 6.98 × 10⁻³ m/day and 2.34 × 10⁻² m/day when exposed to eggs and larvae, respectively. Publication N^o 5936-Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS 39762.     

Exclusion cage studies on the impact of predation on Helicoverpa armigera in cotton

The impact of predation on Helicoverpa armigera was studied in four field cage exclusion trials on cotton in Kenya. H. armigera egg cohorts were introduced inside predator‐free and open control cages, and the impact of local predator populations on the cohort was examined. Fourteen days after inoculation, exclusion cages had four times more larvae than controls, indicating a strong impact of predation. Ants and Anthocoridae were the predominant predator groups. Exclusion cages had more damaged fruiting plant parts (squares, flowers and bolls) than the control. In the absence of predators, natural mortality of H. armigera was greater as cotton matured, and is likely to be linked to the host plant condition.     

Effect of temperature on the life history and demographic parameters of Spalgis epius (Lepidoptera: Lycaenidae), a candidate biological control agent of mealybugs (Hemiptera: Pseudococcidae)

Many species of mealybugs (Hemiptera: Pseudococcidae) are serious pests of economically important crops worldwide. We evaluated the influence of constant temperatures: 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 and 34°C on the life history and demographic parameters of Spalgis epius (Lepidoptera: Lycaenidae), a candidate biological control agent of various species of mealybugs. No eggs completed their development at 14 and 34°C. Egg-to-adult developmental time significantly decreased from 89.9 days at 16°C to 20.4 days at 32°C. The estimated lower temperature threshold of 10.2°C and 416.6 degree-days were required to complete egg-to-adult development. The mortality of immature stages was maximum at 16 and 32°C and minimum at 28°C. The highest lifetime fecundity was recorded at 28°C and it significantly decreased at 32°C. The longevity of adults was about three times more at 16°C than at 30 and 32°C. The net reproductive rate (R ₀) significantly increased with increased temperatures up to 28°C and significantly decreased at 32°C. The mean generation time (T) significantly decreased with increased temperature up to 30°C, but it significantly increased at 32°C. The intrinsic rate of population increase (r _m ) was highest at 30°C. The finite rate of increase (λ) was significantly greater at 30°C than at other temperatures. These data suggest that S. epius can develop, reproduce and survive in a wide range of temperatures and thus could be regarded a potential biological control agent of mealybugs.     

Role of different habitats for the functional response of Crytorrhinus lividipennis (Hemiptera: Miridae) on Nilaparvata lugens (Hemiptera: Delphacidae)

The functional response of a predator, Cyrtorrhinus lividipennis, on the brown planthopper, Nilaparvata lugens, was investigated in two different experimental habitats: a piece of tiller in a petri dish (5.5?cm in diameter) and a rice plant in a net cage (5.5?cm diameter?×?43?cm height) for 24?h at room temperature. In the petri dish experiment, 2nd–5th instar nymphs, adult male, and female C. lividipennis were introduced in separate experiments to eggs of N. lugens at densities of five, 10, 20, 30, and 40 eggs per piece of rice. In the rice plant experiment, each C. lividipennis was introduced to a cage with a rice plant containing N. lugens eggs. After 24?h, the number of dead eggs and remaining eggs were counted and data fitted to three functional response models. Among the three types of functional responses, Type II best described the predator response to host densities in N. lugens in both experimental habitats, according to the logistic regression analysis value. The results showed that C. lividipennis was a more effective predator in the rice plant experiment compared to the disc experiment. Additionally, the searching efficiency and handling time parameters were different in the two different experimental habitats. This may cause errors when applying the functional response to biological control and predator–prey models. Different habitats and other environmental conditions from the experiment and natural rice field have to be considered.     

Artificial diet for continuous maintenance of the maritima earwig Anisolabis maritima (Bonelli) (Dermaptera: Carcinophoridae)

Anisolabis maritima is an important predator for the eggs of the red palm weevil Rhynchophorous ferrugineus. It could be successfully reared in the laboratory, on an artificial diet composed of dry kidney beans, Brewers yeast, chicken, egg yolk, agar, ascorbic acid, mould inhibitors, vitamin B₁₂, folic acid and riboflavin.     

Net mesh size affects production of giant freshwater prawn Macrobrachium rosenbergii cultured in lake‐based cages

Cage culture of freshwater prawns in open waters is prone to the entry of predators and competitors that particularly hamper production. This study was conducted to determine how smaller net mesh sizes to reduce entry of unwanted species inside the cages affects the production of Macrobrachium rosenbergii in lake‐based cages. Juvenile prawns were stocked in cages (7 × 7 × 1.5 m) of two net mesh sizes at 10 individuals m^?2 and cultured for 10 months in a shallow eutrophic lake in the Philippines. The two net mesh sizes were either 5 mm‐mesh B‐nets or and 1 mm‐mesh Hapa nets. Each treatment had four replicates each and was fed based on biomass with commercially formulated feed. Monitoring of various production parameters was done during the two phases of culture: batch phase on days 63 and 127 and the selective harvest phase on days 187, 219, 253, 281 and 313, when the experiment was terminated. For the first 127 days of culture, the weight, percent weight increase, daily growth rate (DGR), specific growth rate (SGR), yield and feed conversion ratio (FCR) were significantly better in prawns reared in the Hapa compared to the B‐nets. During the selective harvest phase the blue claw, orange claw and berried females were selectively harvested and the remaining prawns returned to the cages. After changes in stocking density through culling, ancova was used to compare the effect of mesh size with the total number of prawns returned to the cages as a covariate. Yield was significantly higher in the Hapa nets. Weight, DGR, SGR and FCR were also consistently higher in the Hapa nets, although not always significantly different. The overall better performance of prawns reared in the Hapa net cages was due to: (i) the reduction in the entry of predator and competitor species in the finer‐meshed Hapa compared to the larger mesh B‐net, (ii) more natural food trapped inside the Hapa cages, and (iii) a higher number of selectively harvested prawns, which decreased stocking density in the cages and improved growth. Use of small mesh size nets is recommended in the cage culture of M. rosenbergii in inland natural water bodies.     

Predatory behaviour of Podisus nigrispinus (Heteroptera: Pentatomidae) on different densities of Anticarsia gemmatalis (Lepidoptera: Noctuidae) larvae

The functional response of the predatory bug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) feeding on its prey, Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), was studied in a greenhouse compartment. Each cage enclosed three soybean plants plus two, four, six, eight, 10, 12 or 14 prey larvae. One adult predator was released and kept inside the cages for 24h. The predation rate of adult male P. nigrispinus was highest at densities of eight or more A. gemmatalis larvae with a handling time of 5.76h and an attack rate of 0.68h^?1. Adult females had higher predation rates on plants with 10 or more A. gemmatalis larvae, with a handling time of 3.84h and an attack rate of 0.65h^?1. The maximum number of larvae consumed by males and females of this predator were 4.1 and 6.0 per day, respectively, in groups of three plants. The results suggest that P. nigrispinus may be used in biological control programmes against A. gemmatalis in soybean fields.     

Four‐year successive rearing of Glyptotendipes tokunagai Sasa (Diptera: Chironomidae) under laboratory condition

The dipteran Chironomidae have been commonly used as water quality indicators and toxicity test organisms. Two chironomids, Chironomus riparius Meigan and C. tentans Fabricius, are standard test organisms for toxicity (OECD), but their distribution is limited in Korea. The purpose of this study was to establish a Korean native chironomid species as a toxicity test organism. Glyptotendipes tokunagai Sasa, distributed widely in Korean streams, was selected and reared successively under laboratory conditions for over 30 generations over 4 years. Four G. tokunagai egg masses were collected from the Jungrang stream in Seoul, Korea in April 2007 and introduced to the laboratory for rearing. Room temperature (23.5 ± 3.2°C), larval and adult rearing cages, mating cages, and larval food were appropriately modified from conventional chironomid rearing methods. The number of eggs in an egg mass, hatching rate, and adult body sizes (head width, thorax width, wing width and length, and body length) were monitored every generation. As a result, the number of eggs in an egg mass decreased rapidly in early generations, and then tended to stabilize after the fourth generation (p < 0.05). The mean hatching rate was higher than 75% in all generations. The gender ratio (no. of females/total no. of adults) was 0.24–0.52. The adult body size became significantly reduced in the initial three generations and tended to be stabilized in the following generations (p < 0.05), although it depended on food supply and larval density. This is the first case of chironomid domestication in Korea that has been successfully reared longer than 4 years under laboratory conditions. This reared population of G. tokunagai can be used for various environmental studies such as bioassays, ecological risk assessments, and environmental monitoring.     

Flight activity assessment of the egg parasitoidTrichogramma brassicae (Hym.: Trichogrammatidae) in laboratory and field conditions

A laboratory and a field test for flight initiation ofTrichogramma brassicae Bezdenko (Hymenoptera, Trichogrammatidae) (synonymous toT. maidis Pintureau et Voegele) were developed with the aim to establish a simple, cheap and quick flight quality control method forTrichogramma producers. The flight quality of four strains ofT. brassicae reared onEphestia kuehniella Zeller eggs were compared. The material tested consisted of four strains: two strains reared for two (F2) and 39 to 42 (F39–42) generations onE. kuehniella eggs without storage treatment, a diapause strain reared six generations (F6) onE. kuehniella eggs and a commercial strain also reared onE. kuehniella eggs whose production and storage conditions were unknown. Clear differences in flight activity among strains were observed. Both, the F2 and commercial strain showed significantly better flight activity under laboratory conditions compared to the other strains. Flight field cage experiments were made for comparison between field and laboratory results. Similar differences among strains in field cage experiments were observed when compared to laboratory tests.     

Effect of diet and mating status on ovarian development and oviposition in the polyphagous predator Macrolophus caliginosus (Heteroptera: Miridae)

The mirid bug Macrolophus caliginosus is commercially reared on eggs of Ephestia kuehniella, constituting an effective but expensive factitious food. Artificial diets can decrease the rearing costs of this natural enemy, but developing and evaluating an artificial diet is a very time-consuming activity. In the current study, development and reproduction of M. caliginosus on two artificial diets based on egg yolk were investigated. The artificial diets resulted in longer development and lower adult weights, but survival was comparable with that of control insects fed E. kuehniella eggs. Reproductive potential of the predator reared on factitious and artificial foods was assessed using a dissection method. The influence of nymphal food on fecundity was less important than that of adult food. Adults fed E. kuehniella eggs had a preoviposition period of about 4 days, whereas adults offered only plant material started laying eggs about 7 days after emergence. Ovarian scores at day 7 were higher for females fed E. kuehniella eggs than for those given access only to a tobacco leaf. Ovarian scores were not significantly affected by mating status. In a final test, a parallel comparison of two methods for assessing reproductive response to diet was made. Here, adult couples were offered one of four diets: E. kuehniella eggs, one of two artificial diets or no food. Half of the females were dissected and the other half was held for determining lifetime oviposition. Females fed E. kuehniella eggs had superior ovarian scores and laid more eggs than those fed either artificial diet or those given no extra food. A good correlation (r = 0.97) was obtained between ovarian scores and oviposition data, indicating that dissecting females after 1 week provides a reliable estimate of fecundity as affected by diet quality. Rapid reproductive assessments as used in the current study will help to increase the rate of development of artificial diets and may contribute to more cost effective production methods for augmentative biological control agents.     

Predator interference limits fly egg biological control by a guild of ground-active beetles

We examined whether predator interference could prevent effective conservation biological control of Delia spp. flies, important pests of cole crops, by an assemblage of carabid and staphylinid beetles. In laboratory feeding trials we found that the smaller (<1 cm) beetle species common at our site readily ate dipteran eggs, while the most common large carabid species, Pterostichus melanarius, rarely did. However, P. melanarius did eat several of the smaller beetle species. We conducted two field experiments where we manipulated immigration rates of the ground predator guild and then measured predation on fly eggs. Predation rates were consistently higher in cages where predators were added at ambient densities, compared to cages where ground predators were removed. However, in the second field experiment, when we quadrupled predator immigration rates neither beetle activity-density nor predation rate increased. High immigration rate plots had a higher proportion of P. melanarius in the predator community, compared to plots with beetles added at ambient densities, suggesting that P. melanarius was reducing activity-densities of the smaller beetles, perhaps through intraguild predation. Thus, tactics to improve the biological control of Delia spp. by conserving generalist predators, such as providing in- or extra-field refuges, could be thwarted if the primary predators of fly eggs, small carabids and staphylinids, are the targets of intraguild predation by also-conserved larger predators.     

Function of the web box as an anti-predator barrier in the spider mite,<Emphasis Type="Italic"> Schizotetranychus recki</Emphasis>

Spider mites inhabiting Sasa bamboo show considerable variation in traits believed to be the result of coevolution between predator and prey. In Schizotetranychus recki Ehara inhabiting the hairy leaves of a dwarf bamboo, Sasa senanensis, all quiescent stages, including eggs, appear within web boxes in the leaf hairs of their host plant, and this habit is thought to be a trait involved in predator avoidance. To test this hypothesis, the survival rates of S. recki eggs inside a web box and those freed of a web box were assessed in relation to six predator species that co-occur with the spider mite in the field. The results clearly show that the webbing behavior (web box) of S. recki has a function in avoiding five predator species. However, one predator species, Agistemus summersi Ehara, preyed more on eggs protected by a web box. This suggests that this predator species has a special trait to overcome the nest barriers.     

Interspecific competition and predation between immature Amblyseius fallacis,Amblyseius andersoni,Typhlodromus occidentalis and Typhlodromus pyri (Acari: Phytoseiidae)

Interspecific competition and predation in immature Amblyseius fallacis (Garman), Amblyseius andersoni Chant, Typhlodromus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten were examined in small cages at three egg densities (0, 20 and 80) of two-spotted spider mite, Tetranychus urticae Koch, in the laboratory at 25±1°C,80% RH and 16L: 8D photoperiod. For the six possible between-species comparisons, the large polyphagous A. andersoni always outcompeted the other three predator species, which were either smaller and/or less polyphagous; the small oligophagous T. occidentalis was always eliminated by the other three predator species, which were either larger and/or more polyphagous. The small and polyphagous T. pyri tied with the large and oligophagous A. fallacis. The outcome of the interaction was generally similar at the three prey densities except in (1) the A. fallacis-A. andersoni system where the advantage of A. andersoni over A. fallacis was reduced when 20 or 80 eggs per cage were present at the start of the interaction and (2) the A. fallacis-T. occidentalis system where the advantage of A. fallacis over T. occidentalis increased with prey density. This study indicates that predator size, predator degree of polyphagy and prey density can affect the competitiveness of immature phytoseiids.     

Biology and life tables for the predaceous earwig,Doru taeniatum [Derm.: Forficulidae]

The biology of the earwig,Doru taeniatum (Dohrn), a reported predator ofSpodoptera frugiperda (J. E. Smith), was studied in the laboratory.D. taeniatum under laboratory conditions was easily reared, mated readily and females tended eggs and first instar nymphs.D. taeniatum developed through 4 nymphal instars and reached imago in approximately 30 days. It is an omnivore in the laboratory and capable of developing and reproduction on plant pollen alone, and on Lepidoptera eggs (Sitotroga carealella) (Olivier) alone. Immatures developed most rapidly and females were most fecund when fed either a combination ofS. cereallea eggs and pollen, orS. cerealella eggs alone. Approved as TA 20744 by Director, Texas Agricultural Experiment Station.     

Cryptococcus neoformans in bird excreta in the city zoo of Cali,Colombia

The presence of Cryptococcus neoformans was studied in bird excreta and in the air circulating in and around bird cages in the City Zoo of Cali, Colombia, between August 1994 and April 1995, using a sunflower seed agar culture medium for fungus isolation. A total of 380 samples was studied, 110 from droppings and 270 from Petri dishes placed inside(148) and outside (122) the cages. C. neoformansvar neoformans was found in only two cases, one from bird excreta (0.9%) and the other from air inside a cage (0.7%). The former positive sample was collected from the cracks of a dead tree where two crested caracaras (Polyborusplancus) roosted; the feces were dry, accumulated,and with a pH of 6. The other positive sample was found inside the cage of these birds; however, samples taken in a dispersion study at 0.5, 1, 5 and 10 m around this cage were all negative. It appears that this low isolation rate is due to adequate cleaning and disinfection procedures used in the city zoo of Cali.This revised version was published online in October 2005 with corrections to the Cover Date.     

Physiological effect of the host plant on the suitability ofTetranychus urticae as prey forPhytoseiulus persimilis [Acari: Tetranychidae,Phytoseiidae]

Weight gain of adult femalesPhytoseiulus persimilis Athias-Henriot was determined after they were fed eggs or adult females ofTetranychus urticae Koch reared on either Lima bean (Phaseolus vulgaris L.) or nightshade (Solanum douglasii Dunal). No significant difference was found when the predator was fed eggs ofT. urticae reared on either host. Predators were heavier when fed adult femaleT. urticae reared on bean. Apparently, a factor determining the prey's suitability is incorporated into its hemolymph or tissues and is not restricted to its gut content.