Patterns of niche overlapping and richness among Geocoris species (Hemiptera: Geocoridae) in Iran

Several big-eyed bugs, Geocoris species, are abundant predators in many important agricultural cropping systems. Despite their apparent importance and high visibility little is known about their environmental relationships, niche overlap and species richness. To determine these ecological characteristics of 5 Geocoris species for use in conservation efforts, an extensive sampling was done in 152 localities of Iran. A richness model was developed using a maximum entropy modelling approach (Maxent) and ArcGIS software for the five species based on collection records in conjunction with eight environmental variables. Maps for habitat overlap were created for paired species using ArcGIS 10.2 and ENMTools. The species displayed different overlapping niche ranges from 1.97% to 37.25% in pair-wise comparisons. For species richness three categories (habitats dominated by 0–1, 2–3, and 4–5 species) represented 38.44%, 46.07%, and 15.49% of the modelled landscape, respectively. A direct relationship was found between humidity and the number of species present in different locations. Understanding the degree of ecological overlap between the Geocoris species, and their effective predation of aphids and mites, is critical in designing biological control methods in agroecosystems.     

Relative longevity of adult Nezara viridula in field cages of cotton,peanut, and soybean

Producers in the southeastern USA face significant crop losses from the stink bugs Nezara viridula (L.), Euschistus servus (Say), and Chinavia hilaris (Say) (all Hemiptera: Pentatomidae). Cotton, peanut, and soybean are major agronomic crops and host plants of stink bugs in the region. We conducted a field plot study to measure the relative longevity of adult, unmated N. viridula males and females caged on peanut, cotton, and soybean to test three hypotheses: (1) differences in mortality are associated with differences in host plant food suitability, (2) mortality rates increase with age, and (3) males have higher mortality than females. Using survival analysis, we found that the sex of the individual did not affect survival rates on any of the three host plants. Survival was significantly higher in cotton and soybean than in peanut. Mortality rates increased with age in peanut, but not in soybean or cotton. The frequency of canopy temperatures above 35 °C was higher in peanut than in soybean. Peanut appears to be a less than ideal habitat in terms of canopy temperature and/or food quality for N. viridula adults. Both, cotton and soybean were equally suitable food resources for N. viridula adults prior to maturation of the plants.     

Predation Preference of Typhlodromus Pyri and Kampimodromus Aberrans (Acari: Phytoseiidae) When Offered Con- and Heterospecific Immature Life Stages

The predation preference of singly caged adult females and nymphs of Typhlodromus pyri and Kampimodromus aberrans for con- or heterospecific immature stages as prey was tested in the laboratory. Both polyphagous predatory mite species have been previously shown to interact directly through predation on each other. The present study demonstrated that the adult females of T. pyri and K. aberrans are able to discriminate between con- and heterospecific larvae and protonymphs and that they prefer to prey upon heterospecifics when given the choice. Hunger did not reduce the propensity of the females to prefer heterospecifics over conspecifics. For proto-and deutonymphs the trends followed the results obtained with the adult females, but the preference for heterospecifics was not distinct enough to be significant. In competitive situations reciprocal predation may be a crucial mechanism in the interaction of polyphagous phytoseiid species and may contribute significantly to population persistence. The results are discussed with regard to possible associations between the ability to discriminate con- and heterospecifics and the type of feeding specialization (generalists versus specialists).     

Counterstrategy to Egg Dumping in a Coreid Bug: Recipient Individuals Discard Eggs from Their Backs

The golden egg bug, Phyllomorpha laciniata Vill. (Heteroptera: Coreidae), is the only terrestrial insect in which females oviposit on the backs of female and male conspecifics. Eggs do not survive unless carried by a bug. Herein, I report laboratory observations that egg-carrying individuals actively brush their backs against the host plant seemingly in an effort to rub off eggs. Egg scraping is more common among individuals carrying many eggs than among those carrying only a few eggs. The most recently received eggs were rubbed off first. Females did not avoid laying eggs on the backs of egg-loaded individuals, nor did bugs carrying several eggs resist oviposition attempts more often than unloaded ones. Some males were likely to have fertilized the eggs they scraped off their backs. Laboratory results of active egg removal correspond with egg loss in the field, suggesting that egg scraping may explain egg loss in nature. The data indicate a cost of egg carrying to an individual and an evolutionary arms race between oviposition and discarding behavior.     

Assessment of mite fauna in different coffee cropping systems in Brazil

Agro-ecological diversification may increase natural biodiversity and decrease environmental impacts caused by the intensification of management practices, especially with respect to pest control. This study aimed to evaluate mite populations from surveys in commercial coffee (Coffea arabica) orchards managed in different ways. Four different cropping systems were compared: a conventional system (CS), non-pesticide system (NPS), organic system (OS) and organic agroforestry system (OAS). Mite samples were taken from 24 coffee plantations (n?=?6 for each management strategy). Six leaves per plant were collected from five sampling sites totalling 30 leaves from each plantation. Mites were removed from individual leaves, counted and identified to family level. Amongst the predatory mites, two families were detected; the Phytoseiidae was the most abundant family while the Stigmaeidae, generalist predatory mites, were only found in two management systems (NPS and AOS). Of the two families of phytophagous mites, the family Tenuipalpidae was the most abundant, but rarely found in AOS. The other phytophagous family, Tetranychidae, was less abundant in coffee crops than Tenuipalpidae, but the most abundant phytophagous family in CS. Understanding the relationship between mite populations and management practices can aid in choice of spraying strategies for different coffee management systems.     

两种防治措施下转Bt基因棉田绿盲蝽的发生与为害

2002年在河北省南皮县对2种防治措施下转Bt基因田绿盲蝽LyguslucorumMayre的发生与为害进行的系统调查表明,采用生物农药和低毒化学农药防治4次,Bt棉田绿盲蝽的发生为害较为严重,9月上旬发生高峰期种群密度为7.2头10株,显著高于防治指标,第2代绿盲蝽为害高峰期,叶片被害率为19.4%;采用当地棉农化学防治方法施用农药7次,Bt棉田绿盲蝽发生为害较轻,发生高峰期(8月中旬)种群密度为2.0头10株,第2代绿盲蝽为害高峰期,叶片被害率为4.8%。讨论指出绿盲蝽已成为转Bt基因棉生产中的重要问题,应加快绿盲蝽在转Bt基因棉田的生态调控研究。     

Evaluation of the predatory wasp,Ancistrocerus gazella,for biological control of leafrollers in Otago fruit crops. II. Wasp phenology and seasonal changes in prey composition

The phenology of the predatory wasp, Ancistrocerus gazella (Panzer), colonising artificial nests was studied over 3 years in seven Study Areas in or adjacent to mixed pome and stonefruit orchards in Otago, New Zealand. Each Study Area had three to four nest sites comprising groups of wooden blocks drilled with 6 mm diameter nest tubes 75–150 mm in length. The timing of nest tube colonisation was recorded by observing the presence of nest closures (mud plugs) and their subsequent opening during adult emergence. The nest tubes from some entire nest sites were dissected to determine the stages of development of the wasps and their subsequent emergence, and samples of nest tubes were dissected weekly from a range of nest sites to determine changes in prey composition over the season. A. gazella was found to be primarily bivoltine, but part of each generation entered diapause and a small number of second generation wasps also emerged before winter in warm sites. The adult foraging of each generation was well synchronised with late larval instars of the two generations of three pest leafroller species. However, very low numbers of leafroller larvae were collected because A. gazella was highly polyphagous, predominantly exploiting a sequence of other lepidopterous species. It was concluded that management of A. gazella for leafroller control would be uneconomic but it provides a useful component of the natural enemy complex of pest leafroller species.     

Evidence of population-level lateralized behaviour in giant water bugs, Belostoma flumineum Say (Heteroptera: Belostomatidae): T-maze turning is left biased

Lateralized behaviour occurs in diverse animals, but relatively few studies examine the phenomenon in invertebrates. Here we report a population-level left turn bias in the giant water bug Belostoma flumineum Say (Heteroptera: Belostomatidae) in an underwater T-maze. Individuals made significantly more left turns than right turns, including when they were naïve and first introduced to the maze. Water bugs also showed significantly longer runs of consecutive left turns than right turns (i.e. LLLLL). The length of these runs, however, did not increase with experience in the maze, suggesting that the effect is not the result of learning. There were also no differences in turning bias between male and female water bugs. The proximate mechanism(s) underlying the left turn bias is unknown, but directional cues in the environment were eliminated by rotating the maze 180° between experiments, suggesting the mechanism(s) is endogenous. To our knowledge this is the first study of lateralized behaviour in the Heteroptera or in a swimming invertebrate animal.     

草履蚧一龄若虫的发育历期与防治

在郑州通过室外埋卵观察,草履蚧Drosicha corpulenta Kuwana从1月初开始孵化,孵化后在土里等到2月初开始出土,此时日最高气温在6～8℃之间。若虫出土期约30d,2月中下旬为出土高峰期。经设置14,18,22,26和30℃5个温度梯度观察,草履蚧1龄若虫发育起点温度为7.9℃,有效积温为203.8日.度。利用树干绑缚杀虫药带防治效果达到98%以上。