Management of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae) in strawberry fields with <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> (Acari: Phytoseiidae) and acaricides

The purpose of this study was to evaluate the performance of Neoseiulus californicus (McGregor) for the control of Tetranychus urticae Koch in commercial strawberry fields, under greenhouse conditions, in association or not with the use of acaricides. The N. californicus strain used in this study was tolerant or resistant to several pesticides. Three experiments were carried out in the State of São Paulo, Brazil. For the first experiment, the initial infestation of T. urticae was 87.1 active stages per leaflet. Two applications of propargite were made on the first and the 14th day of the experiment. Approximately 2 h after each propargite application, N. californicus was released at a rate of 3.0 and 1.9 adult mites per plant, respectively, for each application. The population of T. urticae decreased from 87.1 to 2.8 mites per leaflet in the first three weeks. After this period, the population of T. urticae was maintained at low levels (≤1.5 mites/leaflet) until the end of the experiment (10th week). Propargite and dimethoate sprayed on the strawberry field did not affect significantly the population of this predaceous mite. For the second experiment, the infestation of T. urticae was 29.1 mites per leaflet, when the acaricide chorfenapyr was applied on the strawberry field. The release of N. californicus (2 mites per plant) was made 2 weeks after spraying the acaricide. The population of T. urticae was maintained at low levels (≤2.8 mites/leaflet) for 8 weeks (evaluation period). The T. urticae infestations in plots with N. californicus were significantly lower than in non-release plots, for the experiments 1 and 2. In the third experiment, the initial infestation of T. urticae was 40.5 mites per leaflet (55.5 active stages/leaflet on release plants; 25.5 active stages/leaflet on non-release plants). Three releases of N. californicus (average rate of 3.0 adult mites/plant), without any acaricide application, were not sufficient to reduce significantly the T. urticae population in release plots (release plants + non-release plants) in 6 weeks from the first release, however, the spider mite population decreased from 55.5 to 7.8 active stages per leaflet on release plants, during this period. Interplant dispersal of N. californicus was low in this strawberry field with high infestation of T. urticae. The studies indicate the viability of the use of this strain of N. californicus for the control of T. urticae in strawberry fields under greenhouse conditions, especially in association with selective acaricides.     

Diet‐dependent intraguild predation between the predatory mites Neoseiulus californicus and Neoseiulus cucumeris

Based on the hypothesis that matching diets of intraguild (IG) predator and prey indicate strong food competition and thus intensify intraguild predation (IGP) as compared to non‐matching diets, we scrutinized diet‐dependent mutual IGP between the predatory mites Neoseiulus cucumeris and N. californicus. Both are natural enemies of herbivorous mites and insects and used in biological control of spider mites and thrips in various agricultural crops. Both are generalist predators that may also feed on plant‐derived substances such as pollen. Irrespective of diet (pollen or spider mites), N. cucumeris females had higher predation and oviposition rates and shorter attack latencies on IG prey than N. californicus. Predation rates on larvae were unaffected by diet but larvae from pollen‐fed mothers were a more profitable prey than those from spider‐mite fed mothers resulting in higher oviposition rates of IG predator females. Pollen‐fed protonymphs were earlier attacked by IG predator females than spider‐mite fed protonymphs. Spider mite‐fed N. californicus females attacked protonymphs earlier than did pollen‐fed N. californicus females. Overall, our study suggests that predator and prey diet may exert subtle influences on mutual IGP between bio‐control agents. Matching diets did not intensify IGP between N. californicus and N. cucumeris but predator and prey diets proximately influenced IGP through changes in behaviour and/or stoichiometry.     

Toxicity of some insecticides to <Emphasis Type="Italic">Tetranychus urticae</Emphasis>, <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> and <Emphasis Type="Italic">Tydeus californicus</Emphasis>

Three mite species are frequently found on vegetable crops in Italy: the pest Tetranychus urticae Koch (Acari: Tetranychidae), the predator Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) and the unspecialised feeder Tydeus californicus (Banks) (Acari: Tydeidae). In laboratory trials, the direct and residual effects of six insecticides recommended for the control of aphids, whiteflies and thrips in vegetable crops, (Biopiren® plus (pyrethrins), Confidor® (imidacloprid), Oikos® (azadirachtin), Plenum® (pymetrozine), Naturalis® (Beauveria bassiana) and Rotena® (rotenone)), were evaluated for the three mite species. All the products affected the mites and their effect was often favourable towards T. urticae and unfavourable towards N. californicus and T. californicus. Rotenone was more toxic to eggs than females of T. urticae. It was highly toxic to N. californicus and caused the death of all treated females of T. californicus. Pyrethrins and imidacloprid increased T. urticae fecundity, but decreased fecundity of N. californicus. Imidacloprid decreased T. californicus fecundity more than pyrethrins. Beauveria bassiana was not toxic to T. urticae and T. californicus, but induced high mortality in the progeny of treated females of N. californicus. Azadirachtin and pymetrozine were the least toxic to T. urticae and N. californicus, but decreased production of larvae in T. californicus. Implications for integrated pest management on vegetables are discussed.     

Species composition and arthropod pest feeding of phytoseiid mites in a Japanese pear greenhouse

A population survey of spider mites and phytoseiid mites was conducted on Japanese pear leaves in a greenhouse. For the survey, the method to estimate phytoseiid mite species composition using quantitative sequencing was modified to be applicable for phytoseiid mite species inhabiting in the greenhouse. Results show the dominant appearance of Neoseiulus californicus (McGregor), Neoseiulus womersleyi (Schicha), and Neoseiulus makuwa (Ehara) from the end of June to late September and their contribution in spider mite control. PCR-based method to detect the ribosomal internal transcribed spacer (ITS) sequences of spider mites from phytoseiid mites was developed. The method shows sensitivity to detect the ITS sequences of Tetranychus urticae Koch from single N. californicus adult at 168 h after ingestion of the spider mite. PCR-based method to detect the cytochrome c oxidase subunit I sequences of several arthropod pests belonging to Hemiptera, Thysanoptera, and Acari from phytoseiid mites was also developed. Results show that phytoseiid mites prey on Eriophyes chibaensis (Kadono) and Aphis gossypii (Glover), in addition to spider mites.     

In search of artificial domatia for predatory mites

Banker plants can enhance biological pest control by providing both floral resources and appropriate oviposition sites, e.g. through acarodomatia, to predator species. The use of materials mimicking domatia i.e. artificial domatia may be an economically favourable alternative to the use of banker plants bearing domatia. The aim of the present study was to identify materials that are able to host eggs of the Neoseiulus californicus predatory mite but not those of the Tetranychus urticae pest mite. In a laboratory experiment, the oviposition of predatory and phytophagous mites were compared in Petri dishes containing leaves. The different modalities compared were (i) natural domatia of Viburnum tinus or (ii) one of twelve potential artificial domatia materials. The overall oviposition response of predatory mites to all artificial domatia was similar to that of the natural domatia. The oviposition of the Tetranychus urticae pest mite did not increase in response to the artificial domatia. Five artificial domatia hosted as many eggs of the predatory mite as observed in the natural domatia. The effect of the physical properties of artificial domatia was also tested and N. californicus was found to favour the artificial domatia that had high heat retention capacities for oviposition. Three of these artificial domatia were tested on rose plants in a greenhouse experiment; none of which enhanced the biological control on the plants under these conditions. The present study highlights the difficulty in identifying and using suitable artificial domatia as substitutes to banker plants in biological pest control efforts.     

Biological control of twospotted spider mite, <Emphasis Type="Italic">Tetranychus urticae</Emphasis>, with predatory mite, <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>, in strawberries

Greenhouse and field experiments were conducted from 2005 to 2007 to determine the effectiveness of different release times with the predatory mite, Neoseiulus californicus (McGregor), for control of the twospotted spider mite (TSSM), Tetranychus urticae Koch, in strawberries (Fragaria x ananassa Duchesne). The effect of N. californicus releases over time and on development of TSSM populations during a growing season were evaluated. Our hypothesis was that repeated applications of N. californicus, which is currently recommended by biological control companies, might be unnecessary to attain season-long control of TSSM. In greenhouse trials, three treatments consisting of releases of N. californicus at five-day intervals: day 0, day 5, and day 10, and an untreated control were evaluated. The treatment releases significantly reduced TSSM below the control within five days of each release. Neoseiulus californicus significantly reduced TSSM in treatments with high densities (leaflets with ≥ 40 TSSM) below that of treatments with lower densities (leaflets with ≤ 10 TSSM) demonstrating that if released at a predator: prey ratio of 1:10, timing of release does not alter the effectiveness of N. californicus in controlling TSSM. However, we found that if the ratio of predator: prey remains adequate, N. californicus is a more efficient predator at high TSSM densities. Field studies included three treatments consisting of releases of N. californicus at one-month intervals. All treatments significantly reduced TSSM compared with the control plots (no releases). Releases applied early in the season sustained TSSM significantly below those in the control plots for the whole season. Our results indicate that one release of N. californicus is able to sustained control of TSSM in strawberry throughout a growing season if released when TSSM populations are low early in the season in the southeastern United States.     

Two predatory mite species as potential control agents of broad mites

The broad mite is a key pest of various crops worldwide, including chili pepper (Capsicum frutescens), where it is controlled with chemical pesticides. Two phytoseiid predators (Amblyseius herbicolus and Neoseiulus barkeri) and a blattisociid mite species (Lasioseius floridensis) occur in association with the broad mite in Brazil. Predation of broad mites and oviposition rates of A. herbicolus were higher than those of N. barkeri and lowest for L. floridensis. On intact plants, both phytoseiids controlled broad mite populations seven days after their release. In a separate experiment, the predators controlled broad mites on flowering plants during 15 days. After two months, plants with predators produced heavier fruits than plants without predators. Concluding, these two phytoseiid species can control broad mites on chili peppers plants at different densities and over time, reducing production losses, and should be evaluated under field conditions.     

Selection for non-diapause inAmblyseius cucumeris andAmblyseius barkeri and exploration of the effectiveness of selected strains for thrips control

In Europe and North America the western flower thrips,Frankliniella occidentalis, is an important pest in various greenhouse crops, such as sweet pepper and cucumber. Two species of predatory mite are commercially applied for biological control of this pest:Amblyseius cucumeris andA. barkeri. Thrips control is generally successful from March onwards. During winter, however, thrips control by these predatory mites is less effective. An important reason for this is that the commercially applied strains of both mite species enter reproductive diapause under short-day photoperiods, whereas the western flower thrips does not enter diapause. In this paper we report on selection experiments for non-diapause in strains of both mite species, aimed at obtaining predators that do not enter diapause under light- and temperature conditions prevailing in winter. Additional experiments were done to estimate the potential of the selected lines as control agents ofF. occidentalis. Selection for non-diapause proved highly successful in both predatory mite species. In a New Zealand strain ofA. cucumeris diapause incidence decreased from 41% to 0% in about ten generations; in a Dutch strain ofA. barkeri diapause incidence decreased from 67% to 0% in about six generations. Furthermore, selection for non-diapause had no influence on predator performance, measured as predation rate and oviposition rate on a diet of first instar thirps larvae. Rates of predation and oviposition were the same for selected and unselected lines in both species; rates of predation and oviposition were higher forA. cucumeris than forA. barkeri. After 18 months under non-diapause conditions, no less than 92% of a sample of the selected non-diapause line ofA. cucumeris did not enter diapause when tested under diapause-inducing conditions. This indicates that ‘non-diapause’ is a stable trait in these predatory mites. Finally, a small-scale greenhouse experiment in a sweet pepper crop showed that the selected non-diapause line ofA. cucumeris established successfully under diapause-inducing short-day conditions.     

Prey consumption by phytoseiid spider mite predators as affected by diurnal temperature variations

The consumption rate of an ectothermic predator is highly temperature-dependent and is a key driver of pest-predator population interactions. Not only average daily temperature, but also diurnal temperature variations may affect prey consumption and life history traits of ectotherms. In the present study, we evaluated the impact of temperature alternations on body size, predation capacity and oviposition rate of the predatory mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus McGregor (Acari: Phytoseiidae) when presented with eggs of their natural prey, the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). For both predators, mean daily temperature as well as temperature alternation had a substantial impact on the number of prey consumed. At lower average temperatures, more eggs were killed under an alternating temperature regime (20 °C/5 °C and 25 °C/10 °C) than at the corresponding mean constant temperatures (15 and 20 °C). At higher average temperatures (>25 °C), however, the opposite was observed with higher numbers of prey killed at constant temperatures than at alternating temperatures. At 25 °C, temperature variation had no effect on the predation capacity. A similar trend as for the predation rates was observed for the oviposition rates of the phytoseiids. Body size of N. californicus was affected both by average daily temperature and temperature variation, with smaller adult females emerging at alternating temperatures than at constant temperatures, whereas for P. persimilis, temperature variation had no impact on its body size. Our results demonstrate that temperature variations are likely to affect biological control of T. urticae by the studied phytoseiid predators.     

A novel method for protecting slow-release sachets of predatory mites against environmental stresses and increasing predator release to crops

Slow-release sachets of predatory mites are widely employed for controlling small pest arthropods in protected crops. However, environmental stresses can adversely affect the performance of such sachets. To solve this problem, we developed plant-attached shelters that hold sachets of Neoseiulus californicus (McGregor) or Amblyseius swirskii (Athias-Henriot). We conducted laboratory experiments to reveal whether sheltered sachets can protect predators against pesticides and drenching. The numbers of each predator in unsheltered sachets were drastically decreased after spraying with a non-selective pesticide (methidathion), and after continuous spraying (four days) with water, whereas the numbers in the sheltered sachets were not seriously affected by these factors. We also found that more predators (at least for N. californicus) were released from sheltered sachets at different temperatures (25 and 17 °C) than from unsheltered sachets. These results indicate sheltered sachets to be potentially useful for protecting predatory mites against environmental stresses and enhancing their release to crops.     

Performance of Tetranychus urticae and Neoseiulus californicus on strawberry cultivars and assessment of the effect of glandular trichomes

The performance of Tetranychus urticae and its predator Neoseiulus californicus on ten strawberry cultivars was determined in the laboratory. Development time and survival of T. urticae from egg to adult were recorded on Albión, Aromas, Camarosa, Diamante, Festival, Kp, Sabrosa, Selva, Sweet Charlie, and Whitney. Fecundity of newly molted and mated females was recorded during the first 10 days of oviposition. Predation rate and fecundity of N. californicus were tested on Albión, Aromas, Festival, Kp, Sabrosa, and Whitney. Predator females reared on each cultivar were placed individually in experimental units, and the number of eggs per day was counted during 3 days. Cultivars with high hairiness (Albión, Aromas, and Festival) and cultivars with low hairiness (Sabrosa, Whitney and Kp) were identified, to assess the effect on the performance of both species. Development time, survival from egg to adult, and fecundity of T. urticae differed among cultivars. Festival was classified as moderately resistant, Aromas and Kp were moderately susceptible, and the others were intermediate. The number of prey consumed per day per female of N. californicus differed between cultivars and time. Fecundity of N. californicus did not differ among cultivars; however, it did over time. The development time and fecundity of T. urticae did not differ among high and low hairiness cultivars. The glandular hairiness affected neither consumption nor fecundity of N. californicus. According to detrimental and propitious effect on T. urticae and N. californicus performance, respectively, we concluded that Festival and Albión could be used along with this predator in T. urticae management programs.     

Predation,oviposition and conversion rates of the predacious mite,Neoseiulus californicus (McGregor) consuming different densities of Tetranychus urticae Koch,Bemisia tabaci (Genn.) and Thrips tabaci Lind.

Rates of prey consumption, egg production and prey conversion by the predacious mite, Neoseiulus californicus (McGregor) were estimated at different densities of Tetranychus urticae Koch, Bemisia tabaci (Genn.) and Thrips tabaci Lind. in the laboratory. N. californicus females functionally and numerically responded to the increasing densities of T. urticae nymphs, B. tabaci nymphs and T. tabaci larvae showing Holling’s type II. The maximum mean predation and oviposition rates by the predator females devouring T. urticae, B. tabaci and T. tabaci occurred at 15, 10 and 10 prey individuals/day, respectively, followed by the plateau levels at higher prey densities. N. californicus females exhibited the highest feeding and oviposition on T. urticae nymphs, followed by T. tabaci larvae and B. tabaci nymphs. The predator females showed the highest efficiency in converting the prey into egg progeny at 5 individuals/day of the previous prey species, respectively. T. urticae was the most favourable for N. californicus females, followed by T. tabaci and B. tabaci.     

Intraguild Interactions Between the Predatory Mites Neoseiulus californicus and Phytoseiulus persimilis

Species at the same trophic level may interact through competition for food, but can also interact through intraguild predation. Intraguild predation is widespread at the second and third trophic level and the effects may cascade down to the plant level. The effects of intraguild predation can be modified by antipredator behaviour in the intraguild prey. We studied intraguild predation and antipredator behaviour in two species of predatory mite, Neoseiulus californicus and Phytoseiulus persimilis, which are both used for control of the two-spotted spider mite in greenhouse and outdoor crops. Using a Y-tube olfactometer, we assessed in particular whether each of the two predators avoids odours emanating from prey patches occupied by the heterospecific predator. Furthermore, we measured the occurrence and rate of intraguild predation of different developmental stages of P. persimilis and N. californicus on bean leaves in absence or in presence of the shared prey. Neither of the two predator species avoided prey patches with the heterospecific competitor, both when inexperienced with the other predator and when experienced with prey patches occupied by the heterospecific predator. Intraguild experiments showed that N. californicus is a potential intraguild predator of P. persimilis. However, P. persimilis did not suffer much from intraguild predation as long as the shared prey was present. This is probably because N. californicus prefers to feed on two-spotted spider mites rather than on its intraguild prey.     

Combined versus Single Species Release of Predaceous Mites: Predator–Predator Interactions and Pest Suppression

Interactions such as competition, intraguild predation (IGP), and cannibalism affect the development and coexistence of predator populations and can have significance for biological control of commonly exploited pest organisms. We studied the consequences of combined versus single release of two predaceous mite species (Phytoseiidae), with differing degrees of diet specialization, on their population dynamics and the suppression of the carmine spider mite, Tetranychus cinnabarinus Boisduval (Tetranychidae), on greenhouse-grown gerbera. Population growth of the specialist predator Phytoseiulus persimilis Athias-Henriot was greater and population decline steeper when released in combination with the generalist Neoseiulus californicus McGregor than when released alone. In contrast, the N. californicus population grew and declined more gradually when released in combination with P. persimilis, compared to the single species release. The differential impact on each other's population dynamics can be primarily attributed to contrasting properties in competition, IGP, and cannibalism. At the same overall predator density and as long as prey was abundant, the specialist P. persimilis was more strongly affected by intraspecific competition than by interspecific competition with the generalist N. californicus. In contrast, interspecific competition with P. persimilis had a greater impact on N. californicus than intraspecific competition. After prey depletion, the generalist predator N. californicus was more likely to engage in IGP than was the specialist predator P. persimilis. Overall, the study demonstrates that prey specificity has significance for the quality and intensity of predator–predator interactions and indicates potential implications for biological control of spider mites. All predator releases (i.e., either species alone and both species in combination) resulted in reduction of the spider mite population to zero density. Individual release of the specialist P. persimilis led to the most rapid spider mite suppression. Nonetheless, in perennial greenhouse-grown crops P. persimilis and N. californicus could have complementary effects and a combination of the two predators could enhance long-term biological control of spider mites. The potential risks and benefits associated with the release of both species are discussed.     

Influence of photoperiod on Orius thyestes Herring (Hemiptera: Anthocoridae) reproduction and longevity

Several species of Orius Wolff are used in biological control of thrips in protected cultivations in temperate regions, but some of them show reproductive diapause, compromising the efficiency of these agents of biological control. There are no reports on the biology of the neotropical species Orius thyestes Herring under different environmental conditions. The purpose of this work was to investigate the influence of photoperiod on reproduction and longevity of this predator. Nymphs were kept in petri dishes in climatic chambers at 28+/-1 degree C, 70+/-10% RH and under the photoperiods of 12L:12D, 11L:13D, 10 L:14D e 09L:15D. The mating adults were kept in petri dishes with Bidens pilosa L. Asteraceae inflorescences as oviposition substracts and eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) as food. The pre-oviposition and oviposition periods, fecundity and longevity were evaluated and O. thyestes did not show reprodutive diapause in all photoperiod conditions established. The mean number of eggs obtained per female decreased with the reduction of the photophase, with a difference (P < 0.05) between the values obtained in 12h and 9h of photophase. Longevity of females and males under 9h photophase was shorter (P < 0.05) than in all other photoperiods tested. The knowledge of the biology of the natural enemy under different conditions allows to optimise the mass rearing and to predict the performance of the predator in different photoperiods which may occur along the year and in greenhouses.     

Cryptic diversity within grass-associated <Emphasis Type="Italic">Abacarus</Emphasis> species complex (Acariformes: Eriophyidae), with the description of a new species, <Emphasis Type="Italic">Abacarus plumiger</Emphasis> n. sp.

Ricoseius loxocheles (De Leon) (Acari: Phytoseiidae) is often found in coffee crops and is known to feed on coffee leaf rust, Hemileia vastatrix Berkeley and Broome (Uredinales). As the occurrence of coffee leaf rust is limited primarily to the rainy season, the mite may use other food sources to survive during the periods of low pathogen prevalence. It is well known that phytoseiid mites can survive on a variety of food sources, such as herbivorous mites, fungi and pollen. We evaluated the ability of R. loxocheles to survive and reproduce on a diet of Brevipalpus phoenicis Geijskes (Acari: Tenuipalpidae), cattail pollen (Typha spp.), clover rust (Puccinia oxalidis), bee pollen (Santa Bárbara^® dehydrated pollen, Santa Bárbara, MG, Brazil) and coffee leaf rust. Ricoseius loxocheles did not survive or reproduce on any B. phoenicis stages tested (egg, larva, adult). The survival and oviposition of R. loxocheles were directly affected by the presence of coffee rust urediniospores, but not by the presence of the prey. Survival and oviposition of the phytoseiid were similar when fed cattail pollen, clover rust and coffee leaf rust but was lower when fed bee pollen. Our results show that R. loxocheles is not a predator of B. phoenicis but it is able to utilize other resources besides coffee leaf rust.     

Effects of sheltered ground habitats on the overwintering potential of the predacious mite <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> (Acari: Phytoseiidae) in apple orchards on mainland Korea

Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is an effective predator of spider mites. In Korea, it is distributed on Jeju Island, but is never found further north on the mainland. Due to poor natural control of spider mites by native predatory mites in mainland orchards, commercialization of the Jeju Island strain of N. californicus on the mainland is currently being considered. We conducted two field experiments in mainland apple orchards during winter 2008 and 2009 to assess the effects of sheltered ground habitats on the overwintering potential of N. californicus. In the first experiment, all of the N. californicus individuals that were experimentally placed on bare ground died within 27 days, whereas 70% of mites sheltered by fallen apple leaves or urethane foam survived for more than 27 days. In the second experiment, individuals were released directly onto the ground, either with or without urethane foam. More individuals were found within urethane foam plots than in plots without foam. Sheltered ground habitats would be an important factor for N. californicus when selecting overwintering sites, and could eventually lead to enhanced winter survival. On the other hand, no live N. californicus individuals were found by the end of the winter in either experiment, which suggests that N. californicus could not successfully overwinter in the study area, even in sheltered ground habitats.     

Food scarcity reduces female longevity of <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> (Acari: Phytoseiidae)

A commercial strain of Neoseiulus californicus (Spical^®) has a conspicuously long postoviposition period in comparison with other strains of N. californicus or other phytoseiid mites. In many insects and mites, life span is shorter for multiple-mated females than for single-mated females, and is shorter under poor prey conditions than under ample prey conditions. We previously showed that the postoviposition period of multiple-mated females was 40% shorter than that of single-mated females, but that it was never shorter than 30 days. Here we focused on the effect of prey abundance on the postoviposition period. We examined three groups of multiple-mated females: mites that were fed ample prey (group I), mites that were subjected to repeated cycles of 2 days of fasting followed by 2 days of ample prey (group II), and mites that were subjected to repeated cycles of 4 days of fasting followed by 2 days of ample prey (group III). The postoviposition periods of groups II and III were 90% shorter than that of group I. Also the total adult longevity was significantly shorter in groups II and III than in group I. Total egg production in group III was about half that in groups I and II, although the oviposition periods in groups II and III were significantly longer than that in group I. These results suggest that the prolonged postoviposition period in single-mated females of the Spical strain may only appear under laboratory conditions, without multiple mating or starvation.     

Intermittent character of adult diapause in Aelia acuminata (Heteroptera)

The response to photoperiod of field-collected Aelia acuminata was studied by exposing insects to three photoperiodic regimes. After the completion of diapause the insects do not respond to photoperiod: in mid-February the length of the pre-oviposition period is the same under both long and short photoperiods. After the onset of oviposition, insects again become responsive to photoperiod regardless of the time of year: under long day, oviposition lasts until death, whereas under short day the females cease oviposition after about 3 weeks. After a further 2 or 3 months without ovipositing, these females which are still experiencing short-day conditions resume reproduction for a further 4–7 weeks and long-lived individuals have three oviposition periods. A regulatory mechanism is suggested for the alternation between oviposition and diapause.     

Reproductive tables of predatory phytoseiid mites (<Emphasis Type="Italic">Phytoseiulus persimilis,Galendromus occidentalis</Emphasis>, and <Emphasis Type="Italic">Neoseiulus cucumeris</Emphasis>)

Feeding of predatory mites (Phytoseiulus persimilis, Galendromus occidentalis, and Neoseiulus cucumeris) on different life stages of Tetranychus atlanticus under optimal conditions was studied. Daily and total consumption of prey by predators and selection of prey of different life stages were studied for 5 days and for the entire feeding period. Average daily food consumption [number of individuals] for the entire life period of mature mite females constituted 0.43 females + 5.0 [nymphs and males] + 3.4 eggs of Tetranychus atlanticus in P. persimilis; 0.12 females + 3.70 [nymphs and males] + 3.10 eggs in G. occidentalis; and 0.19 females + 4.10 [nymphs and males] + 3.50 eggs in N. cucumeris. During the entire period of feeding, P. persimilis preferred large individuals and at the postembryonic stages selected prey to a greater extent than G. occidentalis and N. cucumeris (61.8 and 55.1%, respectively). The use of a 5-day express-method is possible for estimation of some biological characteristics of phytoseiids that previously consumed the same food for a long period. In other cases, analysis of characteristics for the entire life period is necessary.