Biology, life table and predation of Feltiella acarisuga (Diptera: Cecidomyiidae) feeding on Tetranychus cinnabarinus eggs (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common predatory gall midge, which feeds on many species of spider mites. All major life history and life table parameters of F. acarisuga were determined using the carmine spider mite, Tetranychus cinnabarinus (Boisduval) eggs as prey under laboratory conditions [26.7 ± 2 °C, 75 ± 5% RH, and a photoperiod of l4:10 (L:D) h]. Developmental times of F. acarisuga were 2.6, 7.1, and 6.7 d for eggs, larvae, and pupae, respectively, with an average of 16.4 d from egg to adult emergence. Female immatures development took ≈1 d longer than male immatures did. Adult F. acarisuga lived an average of 12.8 d, and the female adults (13.3 d) lived significantly longer than male adults did (11.9 d). After an average of 1.5 d preoviposition period, each female laid an average of 27.3 eggs in its life span with an average of 2.1 eggs per day and an average of 2.8 eggs on each of its oviposition day. The raw data were analyzed using an age-stage, two-sex life table method that takes into consideration of the variable developmental rates among individuals and between sexes. The intrinsic rate of natural population increase (r), net reproductive rates (R_o), gross reproductive rate (∑m_x), generation time (T), and doubling time (DT), and the finite rate of increase (λ) of F. acarisuga were estimated using the age-stage, two-sex (male and female) life table analysis as 0.122 d⁻¹, 16.19 eggs per female, 20.81 eggs per female, 22.81 d, 1.1298 d, and 5.7 d⁻¹, respectively. Each of the first, second, and third instar larvae of F. acarisuga consumed an average of 35.5, 54.0 and 86.9 T. cinnabarinus eggs per day, respectively. Larvae of F. acarisuga could consume an average of 175.4, T. cinnabarinus eggs, and female larvae consumed 14% more spider mite eggs (187.6 eggs) than male larvae (165.1 eggs). The significance of other life table parameters related to the population and the potential of using F. acarisuga as a biological control agent are discussed.     

Effects of Temperature and Relative Humidity on Development,Reproduction, and Predation in Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae)

The predatory gall midge Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) is a biological control agent for twospotted spider mites on greenhouse vegetable crops. Effects of temperature and relative humidity (RH) on development of immatures, reproduction, and prey capture were determined in order to confirm the suitability of F. acarisuga for use in greenhouses. Developmental time ranged from 10 days at 27°C to 34 days at 15°C. At 20°C, developmental time was significantly shorter at 96% RH than at 84% RH. There was very poor survival of immatures at 64% RH and none at 36%. Lifespan of adult females decreased with increasing temperature, but temperature had no significant effect on number of eggs laid. At 20°C, lifespan was longer at 84 and 96% RH than at 64 or 36% RH. The number of spider mites attacked by 3-day-old larvae over 8 h increased with increasing temperature from 15 to 27°C. The number of mites attacked also increased with increasing RH at 27°C. We conclude that F. acarisuga will complete its life cycle and reproduce under conditions typically found in vegetable greenhouses in northern temperate climates. However, extended periods of low RH (<60% RH) could reduce reproduction and survivorship sufficiently to impair the predator's action against spider mite populations.     

Potential impacts on Japanese fauna of canestriniid mites (Acari: Astigmata) accidentally introduced with pet lucanid beetles from Southeast Asia

To develop a risk-assessment system for small organisms accidentally introduced with imported organisms, we investigated as a first case study parasitic canestriniid mites, which have been imported into Japan via pet lucanid beetles from Southeast Asia. We collected mites from pinned specimens of Japanese lucanids collected before 1999—when the Japanese government lifted a ban on the import of the beetles—and living mites from imported and native lucanid beetles collected after that. No foreign canestriniid was found on any of the native Japanese beetles. Because the mites collected from imported beetles were different from Japanese species, we conclude that the foreign mites have not yet established wild populations in Japan. However, because the Japanese mites migrate between hosts without host physical contact, introduced mites are assumed to be able to migrate from a foreign to Japanese host. In fact, possible contamination was observed in pet shops. We observed host switching in only one direction: Southeast Asian Canestrinia nr spectanda switched to Japanese Dorcus rectus, but Japanese Coleopterophagus berlesei never switched to Indonesian D. titanus. The foreign mites reproduced between 15°C and 25°C, suggesting that the mites could survive in mountainous sites in southern Japan and at low elevations in northern Japan. The ability of foreign parasitic canestriniids to infect and survive on Japanese hosts at temperatures characteristic of much of Japan leads us to conclude that these mites present a potential risk to Japanese endemic canestriniids as well as to native Japanese lucanids.     

An alien Sennertia mite (Acari: Chaetodactylidae) associated with an introduced Oriental bamboo‐nesting large carpenter bee (Hymenoptera: Apidae: Xylocopa) invading the central Honshu Island,Japan

Since 2006, an introduced Oriental bamboo‐nesting large carpenter bee, Xylocopa tranquebarorum, has been recorded from the central Honshu Island, Japan, which is inhabited only by the endemic subspecies, Xylocopa appendiculata circumvolans. Carpenter bees (tribes Xylocopini and Ceratinini) have ecological associations with specific Sennertia spp. in all geographic regions of their distribution, thus it is worried that the introduced carpenter bee has brought non‐indigenous mites into Japan. In their native ranges, X. a. circumvolans and X. tranquebarorum each has specific Sennertia mite faunas: the four Japanese Alloxylocopa bees including X. a. circumvolans have associations with S. alfkeni, while X. tranquebarorum has association with S. potanini in China (except Taiwan) and with S. horrida in South to East Asia including Taiwan. In the present study, we examined phoretic mite fauna on the introduced X. tranquebarorum, and determined whether the mites are indigenous or not based on morphological character and two gene sequences (mitochondrial cytochrome oxidase subunit I gene and nuclear ribosomal internal transcribed spacer). It was found from the result of this study that the non‐indigenous Sennertia mite has invaded Japan with the introduced X. tranquebarorum. We discuss geographic origin of the introduced X. tranquebarorum based on associated mite fauna and potential ecological risk caused by the introduced Xylocopa‐Sennertia association.     

Labiobaetis species of Japan, Taiwan, and Korea, with a new synonym of L. atrebatinus (Eaton 1870) and reerection of the subspecies L. atrebatinus orientalis (Kluge 1983) (Ephemeroptera, Baetidae)

We associated nymphs of Labiobaetis sp. G and Labiobaetis sp. Q from Japan with imagoes reared from nymphs in the field. Labiobaetis sp. G was identified with L. atrebatinus (Eaton 1870) based on characters of the reared male and female imagoes, nymphs, and eggs. We also synonymized a Taiwanese species, L. morus (Chang and Yang 1994), with L. atrebatinus. After further examination of the characters of male imagoes from Japan and Korea and nymphs from Japan and Taiwan, we found them to be correspondent to subspecies L. atrebatinus orientalis (Kluge 1983). Thus, we reerected the subspecific status of L. a. orientalis, although it had been considered not distinguishable from the nominotypical subspecies L. a. atrebatinus. Labiobaetis a. orientalis is distributed in the Russian Far East, Japan, Korea, and Taiwan. We identified Labiobaetis sp. Q with L. tricolor (Tshernova 1928) based on characters of the reared male and female imagoes, nymphs, and eggs. Labiobaetis tricolor was recorded from Japan for the first time.     

Geographic distribution of phytoseiid mite species (Acari: Phytoseiidae) on crops in Okinawa,a subtropical area of Japan

We extensively identified phytoseiid mites co‐occurring with spider mites on crops throughout the islands of Okinawa, southwestern Japan to obtain fundamental information for controlling spider mites in the area using natural enemies. Of the 19 species found, three were new to Japan and eight were new to Okinawa. Neoseiulus womersleyi was the most common species with respect to the distribution range. Following N. womersleyi, six species including Amblyseius eharai were common, whereas N. californicus was not, suggesting that the recent change in dominant species from N. womersleyi to N. californicus observed on the main islands of Japan had not happened in Okinawa. On one small island (Tarama Island) located in the southwestern part of Okinawa, N. womersleyi was not found, and instead N. longispinosus, which is morphologically similar to N. womersleyi and has not been found in Japan, occurred. This suggests interisland differences in the relative frequencies of N. womersleyi and N. longispinosus in Okinawa.     

Predation of entomopathogenic nematodes by <Emphasis Type="Italic">Sancassania</Emphasis> sp. (Acari: Acaridae)

Predation of the entomopathogenic nematode, Steinernema feltiae (Rhabditida: Steinernematidae), by Sancassania sp. (Acari: Acaridae) isolated from field-collected scarab larvae was examined under laboratory conditions. Adult female mites consumed more than 80% of the infective juvenile (IJ) stage of S. feltiae within 24 h. When S. feltiae IJs were exposed to the mites for 24 h and then exposed to Galleria mellonella (Lepidoptera: Pyralidae) larvae, the number of nematodes penetrating into the larvae was significantly lower compared to S. feltiae IJs that were not exposed to mites (control). Soil type significantly affected the predation rate of IJs by the mites. Mites preyed more on nematodes in sandy soil than in loamy soil. We also observed that the mites consumed more S. feltiae IJs than Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae). No phoretic relationship was observed between mites and nematodes and the nematodes did not infect the mites.     

Phoretic dispersal on bumblebees by bromeliad flower mites (Mesostigmata, Melicharidae)

Nectarivorous flower mites (Mesostigmata: Melicharidae) live mostly on hummingbird-pollinated plants in the New World. We observed Proctolaelaps sp. living on Neoregelia johannis (Bromeliaceae) in a coastal rain forest site in south-eastern Brazil. Flower anthesis of this bromeliad lasted a single day. We recorded mites moving into, feeding from, presumably mating and reproducing, and exiting bromeliad flowers within just a single day. We observed three ant species predating flower mites on bromeliads. The main visitor was the bumblebee Bombus morio, which always landed on the inflorescence to access nectar inside the bromeliad flowers. We found Proctolaelaps sp. mites on 47% of 38 bumblebees inspected, with each Bombus hosting 2 mites on average; only adults and mostly female mites (93%) usually found on the bumblebees’ gula region of the head. This is the first study to document nectarivorous flower mites living on a melittophilous host plant using bumblebees for phoretic dispersal.     

Species composition of thrips (Thysanoptera: Thripidae) and spider mites (Acari: Tetranychidae) on cultivated chrysanthemum (Asteraceae) in Okinawa,southwestern Japan

We investigated the species composition of phytophagous thrips and spider mites on cultivated chrysanthemum in Okinawa, southwestern Japan. Eight thrips species belonging to the genera Frankliniella, Microcephalothrips, Scirtothrips and Thrips were found on chrysanthemum leaves. Among them, Thrips nigropilosus was the predominant species irrespective of season, island or cultivation environment (meshed greenhouse or open field), with its infestation frequency being 89% of the fields in which thrips occurred. This high frequency of occurrence suggests that T. nigropilosus is a major pest of chrysanthemum in Okinawa, even though this species has rarely been regarded as an important pest of chrysanthemum or other crops in any other areas. Thrips palmi was the second most dominant (infestation frequency 36%) and other species were scarce (<14%). Tetranychus urticae (green form) was the only tetranychid species on chrysanthemum in our survey. This lack of diversity among spider mites on chrysanthemum is peculiar considering that eight Tetranychus species have been found on vegetables in the same area. Since T. urticae (green form) has been shown to be resistant to a number of pesticides, severe pesticide applications might have simplified the spider mite fauna on chrysanthemum in Okinawa.     

Regular dorsal dimples and damaged mites of <Emphasis Type="Italic">Varroa destructor</Emphasis> in some Iranian honey bees (<Emphasis Type="Italic">Apis mellifera</Emphasis>)

The frequency of damaged Varroa destructor Anderson and Trueman (Mesostigmata: Varroidae) found on the bottom board of hives of the honey bee, Apis mellifera L. (Hymenoptera: Apidae) has been used as an indicator of the degree of tolerance or resistance of honey bee colonies against mites. However, it is not clear that this measure is adequate. These injuries should be separated from regular dorsal dimples that have a developmental origin. To investigate damage to Varroa mites and regular dorsal dimples, 32 honey bee (A. mellifera) colonies were selected from four Iranian provinces: Isfahan, Markazi, Qazvin, and Tehran. These colonies were part of the National Honey bee Breeding Program that resulted in province-specific races. In April, Varroa mites were collected from heavily infested colonies and used to infest the 32 experimental colonies. In August, 20 of these colonies were selected (five colonies from each province). Adult bees from these colonies were placed in cages and after introducing mites, damaged mites were collected from each cage every day. The average percentage of injured mites ranged from 0.6 to 3.0% in four provinces. The results did not show any statistical differences between the colonies within provinces for injuries to mites, but there were some differences among province-specific lines. Two kinds of injuries to the mites were observed: injuries to legs and pedipalps, and injuries to other parts of the body. There were also some regular dorsal dimples on dorsal idiosoma of the mites that were placed in categories separate from mites damaged by bees. This type of classification helps identifying damage to mites and comparing them with developmental origin symptoms, and may provide criteria for selecting bees tolerant or resistant to this mite.     

Experimental evidence for a female sex pheromone in Arrenurus manubriator (Acari: Hydrachnida; Arrenuridae)

We present experimental evidence for a water-borne female-produced sex pheromone in aquatic parasitengonine mites. Water that has contained adult female Arrenurus manubriator Marshall will elicit arrestant behaviour in conspecific adult males, and if the cue is sufficiently strong, the males will assume a readiness posture (with 4th pair of legs held over the back, bent anteromedially at the genuotibial joint) that is typically a precursor to coupling. Water that has not been exposed to female mites does not induce any behavioural response from male mites. Female-conditioned water that has been passed through a C-18 column does not elicit any response from male A. manubriator, while the rehydrated residue from the column does induce arrestant behaviour and may result in the readiness posture. The results from the C-18 extraction indicate that the pheromone is nonpolar in nature. This revised version was published online in July 2006 with corrections to the Cover Date.     

The presence of webbing affects the oviposition rate of two-spotted spider mites, <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Several species of tetranychid mites including Tetranychus urticae Koch (Acari: Tetranychidae) construct complicated three-dimensional webs on plant leaves. These webs provide protection against biotic and abiotic stress. As producing web is likely to entail a cost, mites that arrive on a leaf with web are expected to refrain from producing it, because they will gain the benefit of protection from the existing web. Mites that produce less web may then allocate resources that are not spent on web construction to other fitness-enhancing activities, such as laying eggs. To test this, the oviposition rate of T. urticae adult females was examined on leaves with web. As a control, we used leaves where the web had been removed, hence both types of leaves had been exposed to conspecifics previously and were thus damaged. On leaves with web, the oviposition rate of T. urticae females was higher than on leaves where the web had been removed. Therefore, the presence of web constructed by conspecifics enhanced the oviposition rate of T. urticae females. This provides indirect evidence that mites use the web constructed by conspecifics and thereby save resources that can be allocated to other traits that enhance reproductive success.     

Reproductive morphology of Gastroclonium pacificum (Champiaceae,Rhodymeniales) from Japan

Morphological studies were undertaken on Gastroclonium pacificum (E.Y. Dawson) C.F. Chang et B.M. Xia (Champiaceae, Rhodymeniales) from Japan. We describe the details of male reproductive structures, the procarp and early post‐fertilization stages. This species has a solid axis, with both tetrasporangia and polysporangia, spermatangia are cut off from spermatangial parent cells, and a procarp is composed of a 4‐celled carpogonial branch and two 2‐celled auxiliary cell branches. The mature cystocarp lacks a conspicuous ostiole, a characteristic of the genus Gastroclonium. The most distinctive characteristic of the species is the tela arachnoidea, which is lacking in other species of Gastroclonium.     

Mite communities (Acari,Mesostigmata) associated with <Emphasis Type="Italic">Ips typographus</Emphasis> (Coleoptera,Scolytidae) in managed and natural Norway spruce stands in Central Europe

Previous studies have suggested that forest management practices can influence bark beetle populations as well as those of some associated insects. However, the impact on bark beetle-associated mites, which occur in bark beetle galleries in large numbers, have not yet been studied. The objective of this study was to compare mesostigmatid mite communities associated with the Norway spruce pest Ips typographus in managed and natural forest stands separated by spruce-free belt. The study sites were located in Białowieża National Park (NE Poland) as well as in the Izery Mountains (Szklarska Poręba Forest District — SW Poland), which were destroyed in 1981–1987 by an ecological disaster. In total, 30 Borregard pipe traps containing the commercial attractant Ipsodor W (Chemipan, Poland) were set up at each study site and collected in August 2010. In total, 7214 bark beetles and 1804 mites were collected which were classified into 16 species. We observed differences in the total abundance of mites as well as the total number of recorded mite species. The communities were quite similar, and were generally dominated by populations of Trichouropoda polytricha, Dendrolaelaps quadrisetus and Uroobovella ipidis. The Shannon and Evenness indexes as well as the mean number of mites per sample were not significantly different between forests.     

Three‐year surveillance (2016–2018) of chigger mites vector for tsutsugamushi disease in the Hwaseong‐Si area of Gyeonggi‐Do,Republic of Korea

Owing to climate change, the global resurgence of vector‐borne infectious diseases has emerged as a critical public health issue. Orientia tsutsugamushi is the etiological agent of tsutsugamushi disease (scrub typhus) a mite‐borne acute febrile disease occurring in the Asia‐Pacific region. We investigated the prevalence of tsutsugamushi disease transmitted by chigger mite vectors living on rodents. Using sticky‐type chigger traps for three months during 2016–2018, 1,057 chigger mites were collected (chigger mite index, 1.31) from four locations in the Hwaseong‐si area of Gyeonggi‐do, Republic of Korea. Five species distributed among three genera were identified. In addition, 94 rodents were captured (collection rate: 7.83%) using Sherman live traps over the course of three months (April, October, and November) during 2016–2017. Three rodent species were captured and identified and the striped field mouse (Apodemus agrarius) was the dominant rodent host species in the surveyed area. A total of 10,469 ectoparasitic chigger mites were recovered from the 94 rodents, from which 13 species distributed among four genera were identified. Of the 5,250 chigger mites examined, Leptotrombidium pallidum was most abundant (n = 2,558), followed by L. orientale, L. scutellare, L. zetum, Euschoengastia koreaensis, L. subintermedium, and Neotrombicula tamiyai. Of the examined chigger mites, no groups recovered from rodent hosts tested positive for O. tsutsugamushi. This study provides fundamental regional information on vector‐borne disease data collection in the Hwaseong‐si area, Gyeonggi‐do, and will further contribute to formulating disease control and prevention strategies.     

Use of spinosad and predatory mites for the management of Frankliniella occidentalis in low tunnel‐grown strawberry

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is a major pest of strawberry. The efficacy of three species of predatory mites, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) (both: Acari: Phytoseiidae), and Hypoaspis miles (Berlese) (Acari: Laelapidae), and their compatibility with spinosad for the control of this thrips was evaluated in commercial strawberry in spring. Low tunnel‐grown strawberry was treated with ‘water then mites’, ‘spinosad then mites’, or ‘mites then spinosad’. Predatory mites were released as single‐, two‐ and three‐species combinations. Overall, spinosad‐treated plants had fewer thrips than water‐treated plants (control). In all treatment regimes, each species of predatory mite reduced the number of thrips relative to those plants that received no mites. Predatory mites were most effective in reducing thrips when released after spinosad was applied. Any multiple‐species combination of predatory mites reduced thrips numbers more than single‐species releases. The two‐species combination of T. montdorensis (foliage inhabiting) and H. miles (soil dwelling) was the most effective in suppressing thrips. The next most effective combination was a three‐species release. Of multiple‐species combinations, the two‐species combination of T. montdorensis and N. cucumeris was the least effective in suppressing thrips numbers. The spinosad and mites only temporarily reduced the numbers of F. occidentalis. This suggests that further application of predatory mites, spinosad, or both is required to maintain F. occidentalis populations below an economically damaging level.