Models are useful tools for understanding and improving biological control of arthropod pests by means of natural enemies. Thus, models can be applied to simulate various scenarios in order to identify optimal control strategies. Although simulations can never replace real experiments, they can often serve as guidelines for choosing relevant field experiments and thereby save a lot of laborious and costly field work. Whereas the processes underlying population dynamics (e.g. dispersal, functional response, mutual interference) can be studied under laboratory conditions, large-scaled experiments in the field or in greenhouses are unsuited for this purpose. Instead such experiments may provide information about the patterns (e.g. spatial distributions of prey and predators) generated by the underlying processes. A major purpose of modeling is to link the patterns to the processes that generate these patterns. Petri-dish and single plant experiments have clearly demonstrated the capacity of predacious mite Phytoseiulus persimilis to feed effectively on the two-spotted spider mite Tetranychus urticae. This quickly leads to reductions in the abundance of prey, followed by a decline in predator abundance and eventual extinction. However, when larger systems, consisting of many hundred plants, are infested with the two mite species, extinction of one or both species seems less likely at the system level, although it may still occur at the individual plant level. The qualitative difference between small and large systems with respect to persistence and extinction risks is attributed to the fact that mites move among plants, but to prove that dispersal per se plays a role for the overall dynamics is hard to demonstrate experimentally. To circumvent this problem, I developed a stochastic simulation model of a greenhouse system that explicitly incorporates within and between plant dynamics. The model is used for analyzing a series of experiments with biological control of spider mites in multi-plant systems. In these experiments, the number of plants as well as their connectivity and the numbers of introduced mites were varied in order to examine whether these factors affect e.g. the predator-prey ratio or the time to extinction of one or both species. In my presentation I will also demonstrate an interactive version of the model (called DynaMite). It allows the user to interfere in the system during a simulation so as to mimic the options a grower has in order to prevent losses and to maximize his profit. Such options include spraying with acaricides, releasing predators, and replanting in substitute of damaged plants. By choosing different control strategies, the user may gradually improve his skills according to the principle of learning by experience. The model can be freely downloaded from http://www1.bio.ku.dk/ansatte/beskrivelse/?id=43077

Recognition and discrimination ability of organisms is assumed in numerous biological and ecological contexts. Recognition systems research has originally focused on intraspecific interactions and social recognition but is similarly applicable to interspecific interactions and recognition of environmental features. Common features of recognition systems are at least two participants, called cue bearer (sender) and evaluator (recipient), and three components, expression, perception, and action (Sherman et al. 1997, Liebert & Starks 2004, Mateo 2004, Starks 2004). The recognition systems concept provides a unified framework for studying and understanding recognition processes across biological and ecological contexts. In general, recognition may be indirect, mediated by third organisms or environmental features of the cue-bearer, and direct. I here focus on the latter type of recognition and emphasize how direct recognition processes govern intraand inter-specific interactions within and between plant-inhabiting arthropod species and the plant they inhabit. All species dealt with have relevance in agriculture as either herbivorous pests or natural enemies. Each studied system represents a subset of a multi-trophic community that may occur in natural settings and may be artificially created in greenhouse crops in the course of biological control (Figure 1). The interacting organisms in this community are the predatory mites Phytoseiulus persimilis and Neoseiulus californicus, their prey, the herbivorous two-spotted spider mite Tetranychus urticae and western flower thrips, Frankliniella occidentalis, the host plant of the herbivores, common bean, Phaseolus vulgaris, and a below-ground symbiont of bean, the mycorrhizal fungus, Glomus mosseae. Highlighted topics include mycorrhiza-induced host plant quality recognition by T. urticae (Hoffmann et al. 2008), recognition of and preference towards T. urticae life stages by P. persimilis (Blackwood et al. 2001, 2007), predator recognition and within plant dispersion of T. urticae (Walzer et al. 2008), predator recognition by F. occidentalis and trait-mediated predator effects (Walzer & Schausberger 2008), early learning and recognition of F. occidentalis by N. californicus (Schausberger et al., 2008), intraguild predator recognition with emphasis on P. persimilis and N. californicus (Schausberger & Croft 2000ab, Schausberger & Walzer 2001, Walzer & Schausberger 1999, Walzer et al. 2006), and kin recognition and cannibalism by P. persimilis (Schausberger & Croft 2001; Schausberger 2005, 2007; Schausberger & Hoffmann 2008). The organizational level worked with in the aforementioned studies primarily was the individual level but also included populations and communities; the experimental scale ranged from artificial cages, to detached leaf cultures and whole plants. For each recognition system and ecological context I emphasize the adaptive significance of recognition and indicate, if applicable, the potential population consequences of a given recognition process. In conclusion, I argue that recognition systems are ubiquitous in the studied multi-trophic community and point at the relevance of recognition systems research to biological control.

Varroa destructor Anderson & Trueman is the most injurious parasitic pest of honeybee in the world. Varroa mites had been originally external parasites of Asian honeybee (Apis cerana Fab.) in south eastern Asia. They jumped to European honeybees (Apis mellifera L.) by 1963. Since then they have killed millions of European honeybee colony, which might be susceptible to them, in Asia, Europe, America, and Africa. Also in Korea since Varroa mites were first found in 1968, they have been destructive pests in most of A. mellifera apiaries. Varroa destructor commonly infesting the European honeybees was classified in 2000 as a different species from the Varroa jacobsoni originally identified on Asian honeybees. Varroa mites not only feed the haemolymph of bees, but also introduce virulent viral diseases, and interrupt the development of bee colony. The other external parasitic mite, Tropilaelaps clarea Delfinado & Baker, which was introduced in 1994 from China, has widely spread and also brought damages on honeybees.

Borrelia, which is transmitted by arthropod, is known as an infectious agent to vertebrate, such as Lyme disease (LD) Borrelia and Relapsing fever (RF) Borrelia. LD Borrelia is only transmitted by hard-bodied ticks classified into the Ixodes ticks. In contrast, almost of RF Borrelia was transmitted by soft-bodied ticks, Argasid ticks. Thus so far, the co-evolution was thought to be established between Borrelia and tick. In this study, we found unknown borreliae from imported reptiles and its associated ticks (we preliminary named as ‘REP Borrelia’). Ticks were introduced into Japan with world-wide trading of reptiles. Ticks were classified into genus Amblyomma or Hyalomma. Out of 82 ticks, 76 were positive for PCR of tickmitochondrial gene for 16S rRNA, and we used these 76 ticks for our examination. From 57 ticks (75%), Borrelia turcica and unknown three Borrelia spp. were detected or isolated. In addition, we examined imported reptiles which were infested exotic ticks. A total of 15 reptiles including 5 of Testudo graeca, 1 of T. horsfieldii, 2 of Phelsuma dubia and 7 of Geochelone pardalis were used for isolation study of Borrelia. Borrelia was isolated from 11 reptiles (73.3%) as follows: T. graeca, T. horsfieldii, G. pardalis. It suggested that, these imported reptiles and exotic ticks were highly infected with Borrelia. Phylogenetic analysis based on the DNA sequences of Borrelia, it was indicated that REP Borrelia constituted a cluster which was independent from RF and LD Borrelia. Surprisingly, this REP Borrelia was expected that was transmitted by hard-bodied tick, although it was thought to be diverged from ancestor RF Borrelia. From quantitative analysis of divergence based on 16S rRNA gene, it was expected that REP and RF Borrelia were differentiated around 50 million years ago (MYA). On the other hand, the oldest soft-bodied tick fossil from New Jersey amber was indicated that soft-bodied tick was speciated since ~92 MYA. In fact, soft-bodied tick was already diverged into genus level when RF and REP Borrelia were diverged. This may suggest that the vector switching event was occurred in ancestor REP/RF Borrelia.

In Korea, the backgrounds of predatory mite introduction are increase of the higher income level and the consumer interested in environmental-friendly agricultural products. So, the studies on pest control with natural enemy instead of pesticide have been increased. In early days of natural enemy research in Korea, domestic natural enemies as like Amblyseius womersleyi Evans were attempted for control of spider mites in orchard and greenhouse. As the number of crops and the cultivation area in greenhouse were rapidly increased till now, it is preferred not to find and mass-rear dominant species but introduce the natural enemy species from other countries which are suitable under greenhouse environment (high temperature, low humidity). Chilean predatory mite (Phytoseiulus persimilis Athias-Henriot) was a first natural enemy mite imported from other country and utilized for control of two-spotted spider mite in strawberry greenhouse. The attempt was successful and use of Chilean predatory mite was expanded national widely. After then, pest control by natural enemy has been increased and several companies which produce and sell natural enemies commercially were established. The government recommends the policy, the environmental-friendly agriculture without pesticide for safe and high-quality agricultural product, and gives financial support to farmers. The predatory mites to allow import into Korea in present are 4 species : Phytoseiulus persimilis Athias-Henriot, Amblyseius cucumeris (Oudemans), Hypoaspis aculeifer (Canestrini), and Amblyseius swirskii Athias-Henriot. These predatory mite natural enemies are mainly included in Phytoseiidae (Acari) and introduced and sold to control small animal pest as like spider mites and thrips.

Population density of the citrus red mite, Panonychus citri (McGregor), in Japanese pear orchards remained low until mid-August, even after inoculation of pear leaves with a considerable number of adult female P. citri from May onwards. This raised the possibility that pear leaves contain a natural compound that suppresses an increase of P. citri populations. The rate of development from larva to adult was significantly lower on leaves collected in July than on leaves collected earlier or later, in several years. The population suppression was caused by molting inhibition and ovicidal activity, according to our close observation in the laboratory [Gotoh and Kubota (1997) Exp. Appl. Acarol. 21: 343-356]. To clarify whether a natural pear compound caused this molting inhibition, a methanol crude extract of pear leaves was isolated and added to a newly developed artificial diet, consisting of sodium caseinate, sucrose, levulose, glucose and inositol. The compound extracted from pear leaves resulted in the molting inhibition as observed on pear leaves. Based on infrared and NMR spectral analysis, the compound extracted from pear leaves closely resembled the synthetic acaricide hexythiazox. Furthermore, the LC50-values of the compound extracted from pear leaves for ovicidal activity of P. citri eggs and for inhibition of molting to protonymphs were similar to those of hexythiazox. These results strongly suggest that the molting deterrent extracted from pear leaves was in fact hexythiazox, an acaricide in use on pear trees, rather than a natural product. This suggestion becomes even stronger, considering that the molting inhibition was observed in a hexythiazox-spray year, but not in a non-spray year.

Six kinds of insecticides, fenpropathrin, dicofol, milbemectin, tebufenpyrad, monocrotophos and propargite, were selected for investigating LC50s to local two spotted spider mite(TSSM) strains. The TSSMs were collected from peach (Cheongdo area) and apple orchards (Chungju, Kunwi and Sobo areas) in 2005, from strawberry plastic house (Nonsan and Damyang areas) in 2006 for experiment and some insecticides selected TSSM strains for more than 20 generations were also used. Each strain was clustered by LC50 value got from six selected insecticides treatment. Every insecticide showed about three-fourfold LC50 difference among TSSMs caught in same area. There are no specific differences in LC50 patterns of TSSM to insecticides within peach orchard and among apple orchards. But TSSMs of apple orchard and peach orchard were clustered into different group each other. Grouping of selected TSSM strains with insecticides in lab artificially showed good relationship between action mechanisms of insecticides. In strawberry strains TSSM showed regional differences between Damyan and Nonsan. The TSSMs of Nonsan showed more resistance to Tebyfenpyrad and Propargite, but TSSM of Damyang was more resistant to fenpropathrin than that of Nonsan. The TSSMs selected with monocrotophos and bifenazate, known as acetylcholinesterase inhibitors, and also pyridaben and chlorfenapyr, known as inhibitors of mitochondrial electron transportation, were grouped close respectively.

Neoseiulus womersleyi (Schicha) (Acari: Phytoseiidae) is one of the most important predators of spider mites in Japan. Various characteristics have been studied in this species. However, because there is a lack of genetic markers, genetic diversity within and among populations has not been well elucidated. Microsatellites, short stretches of tandem-repeated 1- to 5- nucleotide sequences, are ubiquitously present in eukaryotic genomes and are highly polymorphic. Their high polymorphism makes them suitable markers for studying intra-specific variation. In this study, we developed microsatellite markers in N. womersleyi, and then examined genetic diversity in their populations. Microsatellite enriched genomic DNA library was contracted and sequenced from a single female adult. Of the 40 plasmids sequenced, 31 plasmids showed microsatellite sequences and 24 plasmids were unique. Finally, we could design primers on three loci. When tested their diversity on one wild and two laboratory populations, five to 18 alleles were detected. The wild population showed highest genetic diversity, and this divergence decreased in rearing populations. To investigate the effects of different rearing conditions, genetic diversity in two rearing populations, which were different in population size, were compared with those in the original wild populations. The allelic richness and gene diversity were not significantly different between wild and large-size populations, while the values were significantly decreased in small-size populations. Thus, 40 to 60 females per generation was sufficient to conserve the genetic diversity in N. womersleyi populations during laboratory rearing. In conclusion, the microsatellite markers developed were useful to evaluate genetic diversity in wild and laboratory populations of N. womersleyi.

Molecular mechanisms of monocrotophos resistance in the two-spotted spider mite (TSSM), Tetranychus urticae Koch, were investigated. The resistant (AD) strain showed ca. 3,565-fold resistance compared to a susceptible (UD) strain. No significant differences in the esterase and gluthathion-S-transferase activities were found between two strains whereas AD showed a 1.9-fold higher mixed function oxidase activity. Acetylcholinesterase (AChE) inhibition assay revealed that the AChE from AD strain is 91-fold less sensitive to monocrotophos, suggestive of the target site insensitivity mechanism. Three point mutations (G228S, A391T and F439W/Y) in the AChE gene (tssmace) appeared to primarily contribute to the reduced sensitivity of AChE as judged by the correlation study of mutation frequency versus resistance levels (LC50) of several field populations. The resulting correlation coefficients of the G228S and F439W mutations were 0.711 and 0.300, respectively, suggesting that G228S mutation may play a more significant role in resistance. The A391T mutation, saturated in all field populations examined, appears to provide a base line resistance.

Terrestrial animals are widely considered to be well protected from damage caused by ambient UV radiation, and thus the direct effects of solar UV-B radiation on arthropods have not attracted a great deal of attention. However, if plant-dwelling arthropods have evolved behavioral adaptations to solar UV-B radiation, but not morphological or physiological adaptations, the resources available to them would be strongly limited. Tetranychus urticae and their dominant natural enemies, phytoseiid mites, usually stay on the lower leaf surfaces. Because of the accumulation of UV-B-absorbing compounds such as flavonoids in the leaves, the upper and lower leaf surfaces provide different UV environments. We tested whether UV irradiation affects survival and reproduction of T. urticae and, if so, whether staying on the lower leaf surfaces is beneficial for their performance in solar UV radiation. Consequently, we observed lethal effects of artificial UV-B irradiation and solar UV radiation on T. urticae. However, by remaining on lower leaf surfaces, the mites could avoid such deleterious effects. These suggest that staying on the lower leaf surfaces is a behavioral adaptation of T. urticae to avoiding harmful solar UV-B radiation. Lethal effects of UV-B irradiation also exerted strong deterrent effects on the hatchability of phytoseiid mites. Additionally, preliminary experiments suggested that phytoseiid mites avoided and quickly escaped from a place irradiated by solar UV. Therefore, solar UV-B radiation may strongly affect the diurnal and spatial patterns of distribution or migration of mite communities on host plant canopies.

Why do two-spotted spider mites (Tetranychus urticae) inhabit on the underside of leaves? Why are diapause females orange? A possible key to answering these questions is ultraviolet (UV) radiation. UV radiation directly damages DNA and produces reactive oxygen species (ROS). ROS also damages DNA, dissociates proteins, and oxidizes lipids. Because mites are small, the UV/ROS-induced damage would be lethal to mites. In non-diapause females, mortalities under UV-C (250 nm) at 0.6 W m–2 and UV-B (300 nm) at 2.4 W m–2 were significantly higher than those under continuous darkness (DD; control). Oviposition rates in such treatments were significantly lower than those under DD. No significant effects for mortality and oviposition rate were observed under UV-A (350 nm) even when the intensity was as high as 2.4 W m–2. In diapause females, the differences in mortalities between all types of UV radiation and DD were not significant. Interestingly, more than half of diapause females escaped from leaf disks under all types of UV radiation, and the escape rates were significantly higher than those under DD and those for non-diapause females. This suggests that diapause females exhibit negative phototaxis. Mites inhabit the underside of leaves in summer with dense vegetation. Most of UV radiation is absorbed and reflected by leaves. Therefore, the underside of leaves is considered a suitable environment for mites to avoid UV radiation, particularly UV-B (UV-C is completely absorbed by the ozone layer). In autumn, leaves start turning yellow and red as winter approaches and finally, fall. During this phenological event, the UV-B level in the plant canopy would increases dramatically while female mites enter diapause with a change in their body color from yellow-green to orange. It is known that the orange color is mainly due to the accumulation of β-carotene, which plays a role as a scavenger of ROS. Therefore, low mortalities observed in diapause females under UV-C and UV-B may be a result of β-carotene accumulation or merely due to the increase in the escape rate. Therefore, whether the escaped diapause females are resistant to UV-C and UV-B damage needs to be confirmed. Our findings suggest that UV radiation is utilized as an effective non-chemical measure to reduce the mite population and that the selection of habitat and change in body color is the mite’s strategy to reduce the deleterious effects of UV-B.

Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseidae) is well known as an effective natural enemy of two-spotted spider mite, Tetrnychus urticae Koch (Acari: Tetranychidae). However, successful biological control usually requires adequate management of temperature. While P. persimilis did suppress T. urticae at moderate condition (20~25oC) in a week or so, the density of P. persimilis was barely increased at cold condition (5~10oC) in three weeks or so. The problem is that winter temperature is too cold for the development and reproduction of P. persimilis in greenhouse for forcing strawberry. Night temperatures in greenhouse were even mostly lower than 6oC. So, winter application of P. persimilis against T. urticae is useless. To avoid damage from T. urticae in early spring season, it was better that the release amount of P. persimilis was double at middle- and late-October, instead of early-November to next early-February. If necessary, the double releasing of P. persimilis might be good for control of T. urticae at middle- and late-February.

To find effective native natural enemies of spider mites in the surrounding vegetation of citrus orchards, we investigated the species composition and seasonal occurrence of phytoseiid mites on Podocarpus macrophyllus, which is one of the major windbreak tree species surrounding citrus orchards in Japan, in Nagasaki prefecture, south-western Japan, from 2006 to 2007. Six species were found: Amblyseius eharai, Euseius sojaensis, Okiseius subtropicus, Typhlodromus vulgaris, T. kishimotoi, and Typhlodromus sp. Amblyseius eharai was the most dominant species and formed more than 60% of the phytoseiid species collected in both years. Typhlodromus vulgaris was the second most dominant species. The other species were rare, except that Okiseius subtropicus was abundant in February in 2006. The density of A. eharai showed two peaks in late June and from late August to early September. The density of T. vulgaris also peaked in late June. However, the density declined thereafter, and remained low, unlike the seasonal occurrence of A. eharai. Podocarpus macrophyllus blooms from early to mid-June and produces a great deal of pollen. Both A. eharai and T. vulgaris developed and oviposited well when they were reared on pollen of Podocarpus macrophyllus as food. Therefore, the increase of these phytoseiid species in June was thought to be due to the supply of pollen of Podocarpus macrophyllus as food.

In Jeju cirtrus orchards, Panonychus citri, citrus red mite is the most important pest requiring 3 times acaricide sprays. In open field conventional orchards, P. citri usually shows three population peaks; from end of Jun to July, from end of Aug. to Sep., from end of Oct. to Nov. However, natural enemy complex and its function regulating P.citri are poorly understood. From the survey of P.citri natural enemy in citrus orchard in Jeju from 2004 to 2006, predatory beetle, Oligota spp. was most abundant. Three predatory mite, N. californicus, Amblyseius eharai, and N. barkeri, were identified. Among them, the predatory mite, Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), was first found in Korea. Even though it was first found, N. californicus was the dominant species occupying 84% of phytoseiid mites. These predatory mites mostly occurred in Jun and peaked at July, which was accorded with the high humidity season of the year. From the survey, the density relationship with P. citri was unclear. From the study conducted in 2005-2007, N. californicus was more abundant in greenhouse citrus (var. Shirahuhi) than in open field orchards; conventional or organic mandarine citrus. In greenhouse citrus, phytoseiid mites showed suppressing P. citri population. As a next step, the inundative biological control study was conducted using commercial strain of N. californicus, which was originated from Jeju, 2005, in greenhouse citrus. One thousand N. californicus per 1a were released 2 times at 10 day interval on citrus leaves when the initial density of P. citri was about 0.2 per leaf. The release effects were variable depending on the field condition. However, N. californicus did successfully reduce P. citri in greenhouse citrus orchards.

Spider mite is the most concerned pest in apple production. This study compared and analyzed the historical changes of two mite pests, Tetranychus urticae koch and Panonychus ulmi (Koch) in 16-30 representative apple orchards in the major apple production area; Gyeongnam, Gyeongbuk, and Jeonbuk province of Korea from 1992 to 2007. Monthly sampling of 100 leaves per orchard provided the basic data of population density of two mite species. Among those orchards, chemical spray history was also analyzed from four orchards, which could be representatives of IPM practitioners. It was found that overall population densities of T. urticae were higher than those of P. ulmi for 16 years. Before 2000, T. urticae was dominant over P. ulmi in most orchards. However since 2000, P. ulmi have occurred more than or as much as T. urticae.. Moreover, although there was large fluctuation of occurrences of two mite species over the years and localities, spider mite pressure appeared to decrease, in general. It seemed to relate the timing of ground cover management with pheromone-based IPM implementation nationwide from late 90s. Panonychus ulmi appeared to rise in April and July in general, fall in August, and go up again in the late season; September-October, while T. urticae appeared to begin to rise in June with July or August peak and sometime with late season second peak in October. Application frequency of acaricide has been dropped from four times in the late 1990s to 2.5 times in the late 2000s.

Neoseiulus californicus (McGregor) is a potential biological control agent of spider mites in orchards. The field occurrence of this species was first reported from citrus orchards in Jeju Island and recently this mite started to be sold as a commercial product in Korea. However, the natural occurrence of N. californicus in the Korean mainland is unclear or quite limited. At this time, it is not certain whether N. californicus can overwinter in the Korean mainland or not. This mite is presently planning to be used as a biological control agent against spider mites in apple orchards of the Korean mainland. The main objective of this study was to investigate natural overwintering sites of N. californicus and possible factor increasing winter survival of this species, to develop effective method for collecting overwintering population of N. californicus. For the first objective, we conducted field survey in two citrus orchards of Jeju in early and late February 2008. Samples were collected from various possible overwintering sites: citrus trees, ground covers and windbreaks. Total 259 phytoseiid mites were collected, 94% of the mites were identified as N. californicus and 98% of them were adult females. Most of N. californicus were collected from ground covers, specially the weed species which had rosette leaves: Youngia japonica (L.) DC. and Erigeron spp. This result seemed to suggest that N. californicus try to hide beneath weed leaves near ground surface during winter to get successful survival. Thus, the second experiments were conducted in Andong from December 2007 to early March 2008. N. californicus conditioned in a greenhouse with natural day length was individually put in a small tube, and the tubes were kept under different ground surface conditions: bare, fallen leaves and urethane foam. When water had been added in the tube, the mites on bare ground had died after one month, while 70% of the mites of the other cover treatments were surviving. In these cover treatments, 7-10% of the mites had survived until two months, and eventually all died within three months. This result showed that hiding under cover structure near ground surface may be effective to increase winter survival of N. californicus. Therefore, collecting weeds which have rosette leaves may be an effective method to estimate of the overwintering possibility of N. californicus in the Korean mainland.

A phytoseiid mite, Neoseiulus californicus was newly found from Jeju citrus orchards in Korea and it is a polyphagous predator of mite and small insect pests as well as plant pollens. Recently in Korean apple orchards, Tetranychus urticae and Panonychus ulmi are imposing similar pest pressure. Even with ample information of this predator interacting with T. urticae, little is known on the interaction with P. ulmi. We investigated temperature effects on life history parameters of N. californicus when feeding on P. ulmi as prey in the laboratory condition to check the possibility to use this predatory mite in apple mite biological control. So, the development, survivorship and life-table parameters of the predator were studied by given mixed stages of P. ulmi as prey under the range of temperatures (15-34°C), RH 75±10%, and photoperiod 16L:8D to determine the effects of temperature. Temperature had a significant effect on mean development time from hatching to adult emergence and other life-history parameters. The results specified that the developmental time is decreased with increasing temperature between 15 and 30oC. Female development times were shorter at 25, 30 and 34°C (3.83±0.07, 3.37±0.24 and 3.53±0.11d, respectively) and were longest at 15°C (15.61±0.22d). Male developmental times were shorter than females ones at each temperature. The highest adult female life span (70.42±3.06d) and oviposition period (35.83±1.43d) observed at 15oC whereas the shortest at 34oC (13.06±1.03 and 7.3±0.94d, respectively). At 25oC, females laid maximum number of eggs (63.94±2) while minimum (16.59±0.98) was at 34oC. In sex ratio, utmost number of females (0.77±0.01) was counted at 25oC and lowest (0.67±0.01) at 34oC. Survivorship during immature development varied from 78.78 to 93.75% with the lowest value recorded at 20 and 34oC. From life table analysis, the shortest generation time (T=10.7d) resulted at 34oC. The highest net reproductive rate (R0=44.31; expected progeny per female) was found at 25oC. The intrinsic rate of natural increase (rm=0.29) and the finite rate of increase (λ=1.33) per day was estimated highest at 30oC. From this study, we found that N. californicus could successfully develop and oviposit vital eggs. Based on these results, we cautiously expect that N. californicus could be used as a biocontrol agent of spider mites in apple orchards when P. ulmi or T. urticae occurs singly or mutually.

Gamasida (Acari, Parasitiformes) is one the most diverse group in mites, and they inhabit in various environments, for example soil, tree canopy, tree trunk, leaves, animal, inter-tidal zone. About 10,000 species have been described in the world, half of them are predatory mites in soil and litter, and they prey on nematodes, small insects and mites. Although many predatory gamasid mites have been recorded from soil and litter in Japan, difference of diversity and difference of species composition of gamasid mites in different soil environments have not surveyed and discussed yet. In the present study, we surveyed soil gamasid mites in urban environment in Sapporo City, Hokkaido, Japan, and compared with gamasid mites in secondary forests (mixed forest, deciduous broad-leaved forest) in and near Sapporo. Our study focused on the following points: 1) difference of diversity in each environment; 2) characteristic taxa in each envrironment; and 3) availability of some taxa as bioindicator to evaluate environment. Number of species and index of diversity were higher in the fauna of secondary forests. Diversity of the families Parasitidae and Laelapidae were higher in urban environment fauna, while diversity of Parholaspidae and Veigaiidae were higher in the forest one. In the forest, mites of the family Zerconidae appeared exclusively, whereas one species of the family Parholaspidae and Parasitidae were dominant in urban mite fauna. Family Zerconidae and some species of Parholaspidae and Parasitidae may be available as bioindicator to evaluate soil environment.

Gamasid mites are free living predators of soil mites, collembolans, nematodes and other small insects in soil surface. We studied the faunal assemblages of gamasid mites in the severely disturbed mountain sites by fire. Total 12 families 55 species were found from this study. From all sites, species in the family of Parholaspidae were dominant; Holaspina alstoni and H. dentatus. Also, Rhodacarus dentitulatus was also abundant regardless of fire disturbance. In control site, Asca aphidioides was also abundant but not in any of the fire disturbed sites. The abundance was highest in control site followed by IC2, IT3 and lower in IT2 and IT1. Species richness was in the same order of abundance ranging from 2.6 to 12.8 per site. In all sites, species diversities were relatively low ranging from 0.6 to 1.7, but it was higher in control site and lower in IT1. Further discussion will be made on the recovery process of soil inhabiting mites.