The distribution of aquatic invertebrate egg masses in relation to physical characteristics of oviposition sites at two Victorian upland streams

1. Various physical variables were measured at rocks potentially used by lotic macroinvertebrates as oviposition sites at multiple locations on two occasions along the Acheron and Little Rivers, south‐eastern Australia. The associations between these parameters and the presence/absence and abundance of aquatic insect egg masses were explored as well as the small‐scale distribution of egg masses on individual rocks. 2. Physical features that characterise oviposition sites of 17 different aquatic taxa are presented. No obvious differences in patterns of oviposition site selectivity were apparent between multiple sampling times or locations. For some common taxa, multivariate analyses revealed that measurements of rock size and local current speed were positively related to the likelihood of an egg mass being present. However there were no consistent relationships between the abundance of egg masses and either of these variables. 3. The small‐scale distribution of egg masses on individual rocks revealed patterns in relation to surfaces that clearly differed as oviposition habitat, such as the underside, upstream and downstream surfaces. Presumably, these patterns are the result of small‐scale variation in flow conditions that characterise these particular rock surfaces. 4. The results of this study indicate that the oviposition strategies of a number of aquatic taxa may be reasonably predictable based on measurable physical parameters. These findings have important implications for future studies wanting to incorporate the adult and egg life history stages of lotic insects into studies of population dynamics.     

Oviposition habitat selection by the mosquito, Culiseta longiareolata: effects of conspecifics, food and green toad tadpoles

Abstract. 1. Ovipositing females should choose egg-laying sites which maximize the growth and survivorship of their offspring. Accordingly, they should avoid habitats with high densities of competitors and predators and should choose sites with adequate food. We tested experimentally the oviposition response of the mosquito, Culiseta longiareolata Macquart, to extra food and two species which are both potential competitors and predators of its offspring: conspecific larvae and green toad ( Bufo viridis ) tadpoles.
2. We conducted the experiment in outdoor artificial pools where wild C. longiareolata females were presented with choices of all combinations of the presence or absence of: (1) C.longiareolata larvae, (2) B.viridis tadpoles, and (3) extra food (a mixture of ground fish food and mouse chow).
3. Oviposition rates averaged approximately 4 times greater in response to extra food.
4. The presence of the tadpoles, particularly later in the experiment when they were larger, caused a significant reduction (approximately 50%) in oviposition rate.
5. We did not detect a statistically significant effect of conspecific larvae on oviposition habitat selection.
6. Our results indicate that Culiseta females choose habitats for oviposition based on food availability. They also tend to avoid habitats containing Bufo tadpoles, presumably to avoid predation and/or competition.     

Relationship between age and colour of hatched eggshells of Ochlerotatus vigilax (Skuse) (Diptera: Culicidae) on an Australian saltmarsh

Abstract The presence of aedine mosquito eggshells in soil has recently been used to delineate oviposition patterns in coastal wetlands. However, the colour of eggshells may reveal information about the oviposition activity of mosquitoes that is not evident from the density and distribution of eggshells alone. This study describes the rate of colour change of newly hatched eggshells of Ochlerotatus (Ochlerotatus) vigilax , the common saltmarsh mosquito. In March 1996, eggshells were buried in soil of five mosquito-breeding sites on Kooragang Island, NSW. Eggshells were graded by colour using Munsell^® soil-colour charts. Seventy-five percent of newly hatched eggshells were black and 25% were dark brown in colour. Black eggshells faded quickly to lighter shades of brown, so that none were recovered 20 months after commencement of the study. Eggshells faded to a median of dark brown after 13 months and medium brown after 2 years. In another study, significant differences in colour frequency between existing saltmarsh and two recently created oviposition sites were found; the latter site being characterised by numerous black and dark-brown eggshells and very few light-brown eggshells. The results suggest that active and inactive oviposition sites may be identified using the frequency distribution of eggshell colours based on large numbers of eggshells, whereas the colour of individual eggshells only coarsely reflects age since eclosion.     

GENETIC VARIATION IN CACTOPHILIC DROSOPHILA FOR OVIPOSITION ON NATURAL YEAST SUBSTRATES

Theory predicts that environmental heterogeneity in space or in time can maintain genetic polymorphism. Stable polymorphisms are expected to be more readily maintained if there are genotype specific habitat preferences. Genotype specific preferences for oviposition sites in Drosophila could be a major factor promoting habitat selection, and thus the maintenance of genetic variation. This hypothesis is being tested using the cactophilic species, D. buzzatii and D. aldrichi, where available evidence indicates a potential for such habitat selection, the habitats (oviposition sites) being yeast species found in the natural environment of these flies (cactus rots). Genetic variation for oviposition preferences was tested using isofemale lines—for D. buzzatii, a total of 60 lines from seven localities widely distributed through the species range in Australia, and for D. aldrichi, 21 lines from three of these localities. Females were given a choice of five yeast species as oviposition sites. Genetic variation for oviposition preferences on these natural substrates was demonstrated. There was significant variation among isofemale lines within populations in their patterns of preferences for oviposition on the five yeast species. However, analyses of preferences for each yeast species separately showed that the genetic variation for preferences relates to only three of the five species. Heritabilities of individual female preferences for these three species were low, ranging up to 9%. Little geographic differentiation was apparent among populations, most likely due to similar selection regimes within each population. Within populations, this kind of habitat selection could act to maintain polymorphisms, both at loci determining the habitat preferences and at other loci in linkage disequilibrium with them.     

Linking movement and oviposition behaviour to spatial population distribution in the tree hole mosquito Ochlerotatus triseriatus

1. Researchers often use the spatial distribution of insect offspring as a measure of adult oviposition preferences, and then make conclusions about the consequences of these preferences for population growth and the relationship between life-history traits (e.g. oviposition preference and offspring performance). However, several processes other than oviposition preference can generate spatial patterns of offspring density (e.g. dispersal limitations, spatially heterogeneous mortality rates). Incorrectly assuming that offspring distributions reflect oviposition preferences may therefore compromise our ability to understand the mechanisms determining population distributions and the relationship between life-history traits. 2. The purpose of this study was to perform an empirical study at the whole-system scale to examine the movement and oviposition behaviours of the eastern tree hole mosquito Ochlerotatus triseriatus (Say) and test the importance of these behaviours in determining population distribution relative to other mechanisms. 3. A mark-release-recapture experiment was performed to distinguish among the following alternative hypotheses that may explain a previously observed aggregated distribution of tree hole mosquito offspring: (H(1)) mosquitoes prefer habitats with particular vegetation characteristics and these preferences determine the distribution of their offspring; (H(2)) mosquitoes distribute their eggs randomly or evenly throughout their environment, but spatial differences in developmental success generate an aggregated pattern of larval density; (H(3)) mosquitoes randomly colonize habitats, but have limited dispersal capability causing them to distribute offspring where founder populations were established; (H(4)) wind or other environmental factors may lead to passive aggregation, or spatial heterogeneity in adult mortality (H(5)), rather than dispersal, generates clumped offspring distributions. 4. Results indicate that the distribution of tree hole mosquito larvae is determined in part by adult habitat selection (H(1)), but do not exclude additional effects from passive aggregation (H(4)), or spatial patterns in adult mortality (H(5)). 5. This research illustrates the importance of studying oviposition behaviour at the population scale to better evaluate its relative importance in determining population distribution and dynamics. Moreover, this study demonstrates the importance of linking behavioural and population dynamics for understanding evolutionary relationships among life-history traits (e.g. preference and offspring performance) and predicting when behaviour will be important in determining population phenomena.     

Oviposition Behavior of Interacting Predatory Mites: Response to the Presence of Con- and Heterospecific Eggs

Oviposition behavior may be affected by the presence of potential future competitors, mates, or predators of offspring. We examined patch choice, oviposition site preference and egg production in the predaceous mites Phytoseiulus persimilis and Neoseiulus californicus (Acari: Phytoseiidae) when given a choice between paired spider mite patches with and without conspecific eggs, with and without heterospecific eggs, and with conspecific or heterospecific eggs. Neoseiulus californicus females had no patch preference and distributed their eggs randomly in all choice situations. This was also the case with P. persimilis females given a choice between patches with and without conspecific eggs and between patches with either con- or heterospecific eggs. Phytoseiulus persimilis females confronted with patches with and without heterospecific eggs preferentially stayed and oviposited in the predator free patches. We discuss the oviposition strategies of P. persimilis and N. californicus with respect to food competition, cannibalism and intraguild predation.     

粘虫(Mythimna separata Walker)选择产卵场所的意义及颜色在定位中的作用

根据粘虫的产卵习性,在田间分别测定了置于活体寄主和干枯植物上的卵块被捕食的概率,结果表明,枯草上面的隐蔽卵块被捕食的概率最低,与雌蛾的产卵习性相符,说明粘虫产卵选择习性有其生物学意义,即有利于躲避天敌。同时,实验结果表明粘虫幼虫的抗饥饿能力要强于甜菜夜蛾,是其对成虫产卵场所长期适应的结果。室内成虫对不同植物的产卵选择与田间相一致,光谱测定结果也表明绿色植物与雌蛾喜欢产卵的植物秸秆的光谱特征和波峰存在显著差异。观测粘虫雌蛾对不同颜色纸张的产卵选择发现,其喜欢在黄褐色纸张上面产卵,产卵量和产卵次数明显高于绿色纸张,而三者的光谱特征存在显著差异。     

星天牛在悬铃木木段上的产卵行为研究

为明确产卵木段粗细对星天牛Anoplophora chinensis刻槽产卵的影响、了解刻槽产卵习性及产卵规律,以不同直径悬铃木Platanus acerifolia木段为产卵材料,通过无选择和选择性产卵试验,测定了星天牛在悬铃木上产卵部位选择,并监测了星天牛的产卵过程。结果表明：星天牛产卵过程主要包括刻槽部位选择、咬槽、产卵和封槽4个阶段。星天牛在不同直径的悬铃木木段上都能刻槽产卵,但木段的粗细对刻槽数量、产卵量的影响差异显著,对空槽率、卵的大小没有影响。刻槽产卵行为主要集中在直径10~15 cm木段。在直径3~5 cm木段上刻槽数量和产卵量最低,显著低于直径大于5 cm的木段。在武汉地区,星天牛产卵高峰期在6月下旬-7月中旬,孵化高峰期在7月中下旬。该结果为深入研究星天牛的生殖行为,精准监测和防控提供参考。     

沿海蝗区东亚飞蝗(Locusta migratoria manilensis)产卵场所选择的Logistic回归模型

以沿海蝗区南大港水库为研究区域,通过2002和2003两年野外450, 50 m规则栅格取样获取东亚飞蝗卵块、植物种类及其密度、土壤特性如含盐量、5 cm含水量、pH、有机质及地形（阴坡和阳坡）等数据,采用多元Logistic回归模型,运用SAS软件筛选出与飞蝗产卵场所选择密切相关的变量,建立用于预测飞蝗产卵场所选择的Logistic回归模型。结果表明用植株密度（veg_d）和土壤含水量（water）所组建的模型能较好地预测飞蝗产卵选择,logP(Y=1)1-P(Y=1)=21.63-76.23water-5.43log(water)-086(veg_d)。利用拟合优度(Goodness of fit)、预测准确性(Predictive accuracy)及模型x2统计(Model chi-square statistic)等指标对模型进行评价的结果表明,所组建的用于预测飞蝗产卵场所选择的Logistic回归模型是可靠的,且能较好地预测事件是否发生。研究结果为区域蝗灾早期预警提供了科学依据和方法,对今后预测飞蝗产卵地点选择及防治决策有较高的实用性和应用价值。     

Oviposition in Culicoides impunctatus under laboratory conditions

We present a laboratory-based examination of oviposition preference in the Scottish biting midge, Culicoides impunctatus (Diptera: Ceratopogonidae). A variety of oviposition substrates were screened in no-choice and choice bioassays for efficacy in eliciting an egg-laying response. Both upper-layer photosynthetic Sphagnum spp. moss and Juncus articulatus infusions were identified as producing increased oviposition under no-choice conditions. During choice trials against a control of damp cottonwool, upper-layer Sphagnum spp. moss produced a significantly greater egg-laying response. These conclusions are interpreted in terms of possible cues involved in oviposition site selection and assessed for future use in colonisation of this troublesome species.     

沿海蝗区东亚飞蝗(Locusta migratoria manilensis)产卵场所选择的Logistic回归模型

以沿海蝗区南大港水库为研究区域,通过2002和2003两年野外450,50m规则栅格取样获取东亚飞蝗卵块、植物种类及其密度、土壤特性如含盐量、5cm含水量、pH、有机质及地形（阴坡和阳坡）等数据,采用多元Logistic回归模型,运用SAS软件筛选出与飞蝗产卵场所选择密切相关的变量,建立用于预测飞蝗产卵场所选择的Logistic回归模型。结果表明用植株密度（veg—d）和土壤含水量（water）所组建的模型能较好地预测飞蝗产卵选择,log（P（Y=1）/1-P（Y=1））=21．63-76.23/water-5．43log（water）-0．86（veg_d）。利用拟合优度（Goodness of fit）、预测准确性（Predictive accuracy）及模型x^2统计（Model chi—square statistic）等指标对模型进行评价的结果表明,所组建的用于预测飞蝗产卵场所选择的Logistic回归模型是可靠的,且能较好地预测事件是否发生。研究结果为区域蝗灾早期预警提供了科学依据和方法,对今后预测飞蝗产卵地点选择及防治决策有较高的实用性和应用价值。