Life-history and feeding habit ofTyphlodromus bambusae,a specific predator ofSchizotetranychus celarius (Acari: Phytoseiidae: Tetranychidae)

Studies on the life history and food habit ofTyphlodromus bambusae Ehara were carried out under aboratory conditions of 25±1°C, 60–80%rh and 159l:d.The egg-to-egg period of the predator which fed on eggs of the long-seta form ofSchizotetranychus celarius (Banks) was longer than those of the three phytoseiid species,Amblyseius eharai Amitai et Swirski,A. longispinosus (Evans) andA. paraki Ehara, which fed onTetranychus urticae Koch. The sex-ratio ofT. bambusae was not significantly different from those of the other three species. The long ovipositional period and the rather constant, low, reproductive rate observed inT. bambusae were remarkable.The intrinsic rate of natural increase (r _m) ofT. bambusae was 0.164 per day and it was very similar to ther _m of its prey,S. celarius. This observation supports the idea that there is a coincidence between the life-histories of spider-mite prey and their specific phytoseiid predators.Although females ofT. bambusae could feed on eggs ofAponychus corpuzae Rimando orSchizotetranychus recki Ehara which cohabit withS. celarius onSasa bamboo, their oviposition rate was lower than that onS. celarius eggs.Schizotetranychus celarius is thought to be a profitable prey species forT. bambusae, whileS. recki andA. corpuzae are only subsidiary, or alternative, prey.     

Egg-depositing behavior as a predator avoidance tactic of Yezonychus sapporensis Ehara (Acari, Tetranychidae)

Spider mites are very small phytophagous organisms living on plant leaves. They possess a diverse array of life types. Such diversity in life type has been supposed to be a result of coevolution between predator and prey, although there is little concrete evidence to support this concept. In Yezonychus sapporensis inhabiting the leaves of a dwarf bamboo, Sasa senanensis, all quiescent stages including eggs appear on the tips of the host leaf hairs during the summer season, and this habit is thought to be a kind of predator avoidance trait. To confirm this, the survival rates of Y. sapporensis eggs deposited on natural sites and experimentally manipulated sites were observed for eight co-occurring predator species. The results clearly showed that the oviposition behavior of Y. sapporensis has a function in avoiding predator attack, at least under experimental conditions. Received: October 26, 2000 / Accepted: December 19, 2000     

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.     

Protein differences detected by two-dimensional electrophoresis in the species complex of Schizotetranychus celarius (Banks)

The species complex of Schizotetranychus celarius (Banks) has been thought to involve three morphologically distinct species, S. celarius, Schizotetranychus longus Sait and Schizotetranychus miscanthi Sait. Furthermore, the former species includes at least three morphs which have not yet been examined taxonomically. In the present study, the protein differences of these species and morphs were examined using two-dimensional electrophoresis. In comparison of protein spot patterns between 11 populations of the S. celarius complex and Schizotetranychus recki Ehara, the former group appeared to be very different to S. recki. The phenogram made based on genetic distance suggested that the species complex includes at least two subgroups: S. miscanthi and S. longus. These results are consistent with the previous taxonomic study. On the other hand, the morphs which had been categorized as S. celarius did not form a distinct cluster.This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education. Science and Cultures, Japan (No. 02640501) and from the Ministry of Agriculture, Forestry and Fisheries (Bio Cosmos Program, BCP-93-I-B-14), and it is the contribution No. E-163 of the Fruit Tree Research Station.     

Parasitism ofLygus lineolaris eggs onCoronilla varia,solanum tuberosum,and three host weeds in southeastern Québec

Parasitism ofLygus lineolaris (Palisot de Beauvois) eggs by three species ofMymaridae, Anaphes iole Girault,Erythmelus miridiphagus Dozier andPolynema pratensiphagum Walley and one species ofScelionidae, Telenomus sp., was investigated at Ste-Anne-de-Bellevue, Québec. The maximum level of field parasitism ofL. lineolaris eggs by individual species was 15.4, 53.8, 70.0 and 16,7%, respectively. Parasitoids were retrieved from eggs ofL. lineolaris inserted in stems and branches ofAmaranthus retroflexus L.,Chenopodium album L.,Coronilla varia L.,Rumex obtusifolius L. andSolanum tuberosum L. Amaranthus retroflexus andS. tuberosum sustained a large population ofL. lineolaris and egg parasitism was high enough to consider it as a potential control factor.      

Intraspecific Variation in Chemical Attraction of Rice to Insect Predators

The olfactory response of predators of the brown planthopper,Nilaparvata lugensStål, to different genotypes of rice (14 cultivars and breeding lines ofOryza sativaL. and 1 wild species,Oryza nivaraSharma et Shastry) was measured in an airflow olfactometer. Odor from rice plants attracted more females of the mirid predatorCyrtorhinus lividipennisReuter than plain air (control) on only 6 of the 15 rice genotypes. Orientation ofC. lividipennistoward volatiles of certain rice genotypes was apparent even when the plants were free of the brown planthopper. However, the predator distinguished between prey-infested and uninfested plants and preferred plants with eggs over plants with nymphs. The predator did not distinguish different stages of plant growth (vegetative, booting, or flowering). Plants artificially injured to simulate brown planthopper oviposition wounds were not as attractive to the predator as plants on which the planthopper had oviposited. The preassay preconditioning on the cultivar TN1 did not produce a predator bias for this genotype. This suggests that rearing effects or chemically mediated associative learning reported for some natural enemies did not influenceC. lividipennis'host response. Results with another predator, the coccinellidMicraspis hirashimaiSasaji, produced less consistent behavior. Planthopper-infested plants attracted more females ofM. hirashimaithan unifested plants in only 1 of the 12 rice genotypes evaluated. Implications for augmenting predators by rice cultivar selection and modification are discussed.     

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.      

Predation of eggs ofSitona hispidulus [Col.: Curculionidae] in alfalfa

The predation on egg populations ofSitona hispidus (Fabricius) [Col.: Curculionidae] in a stand of alfalfa was evaluated in 1982 and 1983. By using pitfall traps, catches of reproductive adults ofS. hispidulus were correlated with catches of carabid species, and potential egg predators were identified for further evaluation. Results indicated that predators removed 28 % of eggs under field conditions.Amara aenea DeGeer was found to be particularly efficient on eggs ofS. hispidulus under caged-field conditions.      

Locking out predators by silk,a new counterattack behaviour in a social spider mite

1. A type of arms race that includes predation, counterattacks and cross‐counterattacks occurs between the phytophagous mite Stigmaeopsis nanjingensis (Ma et Yuan), which lives in self‐woven nests and exhibits cooperative sociality, and its specialised phytoseiid mite predator, Typhlodromus bambusae Ehara. 2. First, the efficiency of the S. nanjingensis (prey) counterattacking T. bambusae (predator) was observed. The prey females frequently locked the immature predators out of their nests using silk web, and the predators subsequently died of starvation. Furthermore, the prey males often killed immature T. bambusae mites after they invaded the nests. 3. This reversal of roles in the predator–prey system was then re‐reversed (returned to a normal state) by the behaviour of T. bambusae females. Immature predators could maintain their predacious natures due to the presence of attending adult females, which are able to cope with the prey counterattack behaviours.     

Consumer trait variation influences tritrophic interactions in salt marsh communities

The importance of intraspecific variation has emerged as a key question in community ecology, helping to bridge the gap between ecology and evolution. Although much of this work has focused on plant species, recent syntheses have highlighted the prevalence and potential importance of morphological, behavioral, and life history variation within animals for ecological and evolutionary processes. Many small‐bodied consumers live on the plant that they consume, often resulting in host plant‐associated trait variation within and across consumer species. Given the central position of consumer species within tritrophic food webs, such consumer trait variation may play a particularly important role in mediating trophic dynamics, including trophic cascades. In this study, we used a series of field surveys and laboratory experiments to document intraspecific trait variation in a key consumer species, the marsh periwinkle Littoraria irrorata, based on its host plant species (Spartina alterniflora or Juncus roemerianus) in a mixed species assemblage. We then conducted a 12‐week mesocosm experiment to examine the effects of Littoraria trait variation on plant community structure and dynamics in a tritrophic salt marsh food web. Littoraria from different host plant species varied across a suite of morphological and behavioral traits. These consumer trait differences interacted with plant community composition and predator presence to affect overall plant stem height, as well as differentially alter the density and biomass of the two key plant species in this system. Whether due to genetic differences or phenotypic plasticity, trait differences between consumer types had significant ecological consequences for the tritrophic marsh food web over seasonal time scales. By altering the cascading effects of the top predator on plant community structure and dynamics, consumer differences may generate a feedback over longer time scales, which in turn influences the degree of trait divergence in subsequent consumer populations.     

Seed dispersal by the Florida box turtle (<Emphasis Type="Italic">Terrapene carolina bauri</Emphasis>) in pine rockland forests of the lower Florida Keys,United States

Seed dispersal by animals is one of the most important plant-animal mutualisms, but saurochory, the dispersal of seeds by reptiles, has received little attention. We investigated the role of the Florida box turtle (Terrapene carolina bauri) as a seed dispersal agent in pine rockland forests of the lower Florida Keys and examined the effect of turtle digestion on seed germination. We obtained seeds of 11 species with fleshy fruits and 2 species with non-fleshy fruits (a grass and legume) from the feces of 145 box turtles collected on Key Deer National Wildlife Refuge from 1999 to 2000. We planted the seeds of nine species and germination percentage (percentage of seeds that germinated during the experiment) varied from 10% to 80%. Comparative germination experiments were conducted with Thrinax morrissii, Serenoa repens, and Byrsonima lucida. We compared the germination percentage and germination rate (number of days from planting to seedling emergence) of seeds from three treatments (seeds recovered from feces, control seeds with pulp, and control seeds without pulp) and continued these experiments for up to 2 years. Passage through the box turtle digestive tract greatly enhanced the germination percentage and germination rate of S. repens, but decreased the germination percentage of B. lucida and T. morrissii, and decreased germination rate for T. morrissii. Subsequent destructive seed viability tests revealed that many ungerminated T. morrissii seeds remained viable, suggesting long-term seed dormancy may occur, even after passage through the turtle digestive system. In addition, the proportion of ungerminated seeds which remained viable was greater for seeds recovered from turtle feces than from control seeds with pulp. Furthermore, removal of fleshy pulp either manually or by the turtle digestive system may allow T. morrissii to escape insect predation.     

Caractères taxinomiques et spécificité dans le genreAsplanchna (Rotifère)

A comparative analysis of eight characters in two clones ofA. brightwelli and a clone ofA. intermedia, fed withParamecium orBrachionus, is made to determine the intraclonal, interclonal and interspecific variations in this complex of species.The trophi morphology appears the most species specific criterium whereas the other features (size of males, diameter and ornamentation of resting eggs, nuclear number in syncytial glands) show variability, either genetic or related to environmental conditions. The variation observed in the ornamentation of resting eggs and in the nuclear number of vitellogen was distributed along a continuous gradient.

     

Biological studies of the predacious miteTyphlodromus pelargonicus a predator of the two spotted spider miteTetranychus urticae on cucumber plants [Acari: Phytoseiidae; Tetranychidae]

The predacious miteTyphlodromus pelargonicus El-Badry preyed on the different developmental stages of the two spotted spider miteTetranychus urticae Koch. The development was quickest and the number of prey consumed was highest when individuals were maintained on eggs compared with nymphs or adult female stages. The predator was able to develop and reproduce on the eriophyid miteEriophyes dioscoridis. Soliman & Abou-Awad, nymphs of the tobacco whiteflyBemisia tabaci (Genn.) and pollen grains ofPhoenix dactylifera andRicinus communis. The average number of eggs/♀/day was 1.4, 0.7, 1.2 and 0.9 on eriophyid, whitefly,Ph. dactylifera andR. communis respectively.      

Sequences affecting the regulation of solvent production in<Emphasis Type="Italic"> Clostridium acetobutylicum</Emphasis>

The high solvent phenotype of Clostridium acetobutylicum mutants B and H was complemented by the introduction of a plasmid that contains either an intact or partially-deleted copy of solR, restoring acetone and butanol production to wild-type levels. This demonstrates that the solR open reading frame on pSOLThi is not required to restore solvent levels. The promoter region upstream of alcohol dehydrogense E (adhE) was examined in efforts to identify sites that play major roles in the control of expression. A series of adhE promoter fragments was constructed and the expression of each in acid- and solvent-phases of growth was analyzed using a chloramphenicol acetyl-transferase reporter system. Our results show that a region beyond the 0A box is needed for full induction of the promoter. Additionally, we show that the presence of sequences around a possible processing site designated S2 may have a negative role in the regulation of adhE expression.     

Development and evaluation of an enzyme-linked immunosorbent assay to detect Pieris rapae remains in guts of arthropod predators

An enzyme-linked immunosorbent assay (ELISA) was developed to detect remains of Pieris rapae L. (Lepidoptera: Pieridae) immature stages in the guts of field collected arthropod predators. The assay can be used to help ascertain the relative importance of arthropod predator species in suppressing P. rapae in cabbage, Brassica oleracea var. capitata L. The ELISA is sensitive to all immature stages of P. rapae, although first and fifth instars can be detected more readily than eggs or pupae and third instars showed intermediate detectability. Assays on whole body homogenates of predators readily detected predation on P. rapae first instars by all seven of the predator species tested, although response generally declined with increasing predator size. Together the results show that the P. rapae ELISA possesses a sufficiently high level of sensitivity and specificity to be a useful tool in helping to elucidate the roles of arthropod predator species in reducing populations of P. rapae in cabbage.     

Fusarium solani invader of the eggs of the insectPanstrongylus geniculatus in a vivarium

A strain ofFusarium solani sensu Snyder & Hansen invaded the eggs of the insectPanstrongylus geniculatus in a vivarium. None of the invaded eggs hatched. To establish experimentally the pathogenicity of thisFusarium species against the eggs ofP. geniculatus, the fungus and the eggs were incubated together under different relative humidities and temperatures. At 64% relative humidity and 26 °C, the fungus grew well colonizing and penetrating all of the chorions.Three embryos died and were also colonized byF. solani. Only 4 nymphs hatched and survived to day 20. It is concluded that the isolate ofF. solani was capable of colonizing and invading the chorion of the eggs under certain humidity and temperature conditions and cause the death of the embryos.     

Genetic variability in the reactive distance inTrichogramma brassicae after automatic tracking of the walking path

Efficiency of hymenopterous parasitoids to control pests in a biological control release program probably increases with increasing searching ability of the females, which, in return, likely depends on the distance from which females perceive their hosts (i.e., reactive distance). In this study, we first analyse this hypothesis with the help of a stochastic model simulating the walking path of isolatedTrichogramma females during their searching behaviour. Then, this reactive distance is estimated using automatic recording and analysis of the walking path of female wasps. Finally, the genetic variability for this trait is analysed in aTrichogramma brassicae Bezdenko (Hym.; Trichogrammatidae) population. Three types of hosts were used: Eggs ofEphestia kuehniella Zeller (Lep.; Pyralidae), eggs ofMamestra brassicae L. (Lep.; Noctuidae) and 0.45 mm glass beads.M. brassicae eggs are perceived from 4.01±0.15 mm, which is a significantly longer perceptive distance than forE. kuehniella eggs (3.69±0.10 mm) and glass beads (3.67±0.10 mm). Moreover, whatever the host tested, a significant genetic variation is observed in this trait in the population studied. The ecological and evolutionary implications and the agronomical importance of these results are discussed.     

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.     

Tree regeneration responses in a lowland Nothofagus-dominated forest after bamboo dieback in South-Central Chile

The bamboo Chusquea quila (Poaceae:Bambuseae) is the most abundant understory species ofNothofagus-dominated forests at low elevations inthe Chilean Lake District. Species of this genus strongly inhibit theestablishment and growth of tree species, especially those of the genusNothofagus. At intervals of many years, this bambooflowerssynchronously and dies, creating large-scale disturbances. The mainobjective of this study was to determine the influence of bamboo dieback ontreeregeneration, especially of shade-intolerant species. The forest studiedis a remnant stand of old-growth forest dominated by emergent individualsof N. obliqua and Eucryphiacordifoliawhich project about 10 m above a main canopy formed byAextoxicon punctatum, Laureliaphilippiana, and Podocarpus saligna. Treeseedlings that established prior to bamboo dieback were recorded in six gapsdensely covered by bamboo. After the dieback event in the early 1990's,recruitment, height growth and survivorship were monitored in four gaps duringtwo growing seasons. After the synchronous mass flowering and death ofChusqueaquila, both reorganization of advance regeneration and new seedlingrecruitment were observed in gaps. The advance regeneration consisted mainly ofthe shade-tolerant species A. punctatum,L. philippiana, and Amomyrtus luma.These species together with E. cordifolia accounted forover 90% of the total individuals in gaps. During the following twoseasons, c. 40% of the advance regeneration either died or was damaged.Root suckers of E. cordifolia and L.philippiana were taller and grew faster than the seedlings of otherspecies. Nothofagus obliqua was unable to establishadvanceregeneration in gaps formerly dominated by bamboo. New recruitment resulted inthe synchronized establishment of treeseedlings, especially less shade-tolerant species such as N.obliqua, Aristotelia chilensis,Rhaphithamnus spinosus, and E.cordifolia. These species recruited into the gaps almost entirelyduring the first season right after the bamboo dieback. However, by the end ofthe second season, these species had a lower density due to a combination oflower recruitment rate, shortened recruitment period, and greater mortalityratecompared to the shade-tolerant species. New bamboo seedlings grew fasterand were more abundant than tree seedlings, except for root suckers (bothnew establishment and advance regeneration) of E.cordifolia which is more likely to successfully recruit into thecanopy. Seedlings of N. obliqua compete poorly with bambooseedlings; its successful recruitment may require bamboo flowering coincidentwith a mast seed year for the tree species.     

Predatory behaviour ofScatophaga stercoraria under laboratory conditions

Laboratory experiments tested the effectiveness ofScatophaga stercoraria (L.) as a predator of various insect species. Photophases, ages and gender of predators and effects of dung presence on predation rates were compared for either sex using counts of prey cadavers, behavioral observations and oviposition rates. Males consistently killed more prey than females, but longer photophases did not significantly increase daily predation rates. Nine to 10-day-old flies approaching sexual maturity achieved highest predation rates. Dung was found to affect predatory behaviour but not cumulative predation. Predatory behaviour of sexually mature males was more affected than female behaviour by the presence of dung, whereas sexually immatures flies showed no response to dung presence. Preconditioning ofS. stercoraria adults using 3 prey species of different sizes did not affect the prey chosen in subsequent random choice experiments. Larger prey species such asMusca domestica (L.) orDelia antiqua (Meigen) were preferred toDrosophila sp. by both sexes ofS. stercoraria. This species may be a useful predator for future integrated pest management techniques in vegetable crops or control of house flies in barns.