Predator foraging behavior in response to perception and learning by its prey: interactions between orb-spinning spiders and stingless bees

Although rewarded bees learn and remember colors and patterns, they have difficulty in learning to avoid negative stimuli such as decorated spider webs spun by Argiope argentata. A. argentata decorates its web with silk patterns that vary unpredictably (Fig. 1) and thus foraging insects that return to sites where spiders are found encounter new visual cues daily. Stingless bees can learn to avoid spider webs but avoidance-learning is slowed or inhibited by daily variation in web decorations (Figs. 3,4; Tables 1,2). In addition, even if bees learn to avoid decorated webs found in one location, they are unable to generalize learned-avoidance responses to similarly decorated webs found at other sites. A. argentata seems to have evolved a foraging behavior that is tied to the ways insects perceive and process information about their environment. Because of the evolutionary importance of bee-flower interdependence, the predatory behavior of web-decorating spiders may be difficult for natural selection to act against.     

A stingless bee (Melipona panamica) indicates food location without using a scent trail

The study of location specification in recruitment communication by bees has focused on two dimensions: direction and distance from the nest. Yet the third dimension, height above ground, may be significant in the tall and dense forest habitats of stingless bees. Foragers of the stingless bee Scaptotrigona postica recruit to a specific three-dimensional location by laying a scent trail. Stingless bees in the genus Melipona are thought to have a more sophisticated recruitment system that communicates distance through sounds inside the nest and direction through pointing zig-zag flights outside the nest. However, prior research on Melipona has not examined height communication or even established that foragers can recruit newcomers to a specific location. We used identical paired feeders to investigate recruitment to food in M panamica on Barro Colorado Island, Panama. We trained foragers from an observation hive to one feeder and monitored both feeders for the subsequent arrival of newcomers. We changed the relative positions of the feeders to test for correct direction, distance, and canopy-level communication. A 40-m canopy tower located inside the forest enabled us to examine canopy-level communication. We found that M. panamica foragers can recruit to a specific (1) direction, (2) distance, and (3) canopy level. To test the possibility that foragers accomplish this by means of a scent trail, we placed the colony on one shore of a small cove and trained bees over 116 m of open water to a feeder located on the opposite shore. We also placed a second feeder on this shore, equidistant from the colony but 20 m from the first feeder. Significantly more newcomers consistently arrived at the feeder visited by the foragers. Thus foragers evidently do not need a scent trail to communicate direction. Inside the nest, a forager produces pulsed sounds while visibly vibrating her wings after returning from a good food source. She is attended by other bees who cluster and hold their antennae around her, following her as she rapidly spins clockwise and counterclockwise. Locational information may be encoded in this behavior. However, foragers may also directly lead newcomers to the food source. Further experiments are planned to test for such piloting and other communication mechanisms.     

Daring females,devoted males,and reversed sexual size dimorphism in the sand-dwelling spider <Emphasis Type="Italic">Allocosa brasiliensis</Emphasis> (Araneae,Lycosidae)

Sexual selection theory predicts that a higher investment in offspring will turn females into the selective sex, while males will compete for accessing and courting them. However, there are exceptions to the rule. When males present a high reproductive investment, sex roles can reverse from typical patterns, turning males into the choosy sex, while females locate males and initiate courtship. In many spiders, males are smaller than females, wandering in search of sedentary females and maximizing the number of copulations. In the present study, we present findings on the sand-dwelling wolf spider, Allocosa brasiliensis, evidencing a reversal in typical courtship roles reported for the first time in spiders. Males were bigger than females. Females located males and initiated courtship. Copulation always occurred in male burrows and took place mainly in long burrows. Males donated their burrows to the females after copulation, closing the entrance before leaving with female cooperation from inside. Males would provide females with a secure place for ovipositing, being exposed to predation and diminishing their future mating possibilities until constructing a new burrow. The cost of vacating the burrow and losing the refuge in an unpredictable habitat, such as sand dunes, would explain the courtship roles reversal in this spider species. Results turn A. brasiliensis as a promising model for discussing the determinants of sex roles and the pressures that drive their evolution and maintenance. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

中国虎纹捕鸟蛛神经毒素肽基因的克隆及在酵母中的表达

从中国珍稀毒蜘蛛种虎纹捕鸟蛛的粗毒中分离纯化的虎纹捕鸟蛛毒素-Ⅰ(HWTX-Ⅰ)是含33个氨基酸的多肽.有关实验已证实,HWTX-Ⅰ是一种作用于突触前膜的神经毒素和高阈值钙通道抑制剂,在电刺激时HWTX-Ⅰ也影响交感神经释放肾上腺素和迷走神经释放乙酰胆碱,这些结果表明,HWTX-Ⅰ具有潜在的镇痛活性.本文报道通过RT-PCR方法克隆、测定了HWTX-Ⅰ的cDNA序列.在此基础上,以pPIC9K为表达载体和GS115为宿主,筛选His Muts克隆,以甲醇为诱导剂,成功地构建并在毕赤酵母系统分泌表达HWTX-Ⅰ基因.进一步分析HWTX-Ⅰ表达产物,生物活性实验观察到酵母表达体系所获得的HWTX-Ⅰ产物具有与天然HWTX-Ⅰ相似的生理活性.图4参10     

Different policing rates of eggs laid by queenright and queenless anarchistic honey-bee workers (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Worker-reproduction is rare in queenright honey-bee colonies. When workers do lay eggs, their eggs are normally eaten by other workers presumably because they lack the queen's egg-marking signal. Workers use the absence of this queen signal to enforce the queen's reproductive monopoly by policing any worker-laid eggs. In contrast, in anarchistic colonies, the majority of the males arise from worker-laid eggs. Anarchistic worker-laid eggs escape policing because workers perceive anarchistic eggs as queen-laid. However, in this study, we show that eggs laid by queenless anarchistic workers do not escape policing and have very similar removal rates to worker-laid eggs from queenless wild-type (i.e. non-anarchistic) colonies. This suggests that, under queenless conditions, eggs laid by anarchistic workers lose their chemical protection and are therefore no longer perceived as queen-laid. Hence, the egg-marking signal seems to be only applied to eggs when queen and brood are present. This suggests that in the absence of queen and brood, the biosynthetic pathway that produces the egg-marking signal is switched off.Communicated by L. Keller     

Cooperative prey capture by young subsocial spiders

Matriphagous young of a subsocial spider Amaurobius ferox exhibit collective predation during their post-maternal social period. In this paper, we examine functional mechanisms of collective predation by sibling groups. Predation efficiency increased with increasing number of individuals within each group. Solitary or paired individuals were generally unable to capture a 20 mg cricket. In larger groups, more individuals participated and captured the prey more quickly. Some siblings did not take part in paralyzing prey, but later consumed it. The proportion of these profiteers within a group increased with the group size. Presented with prey of different sizes (1, 5, or 40 mg), siblings were most aggressive towards each other when predating on 5 mg prey. Prey of this size could be captured by a single individual and yet were sufficiently large for more than one individual to eat. Siblings were much less aggressive towards one another during the capture of 40 mg prey, which require the assistance of other individuals to capture. By providing the same mass of prey in different numbers of individuals (a single cricket of 40 or 40 mg of first-instar crickets), we tested the influence of cooperation on the post-maternal social period. We found no difference in the development of young during the social period nor the timing of dispersal and the body mass of dispersing individuals. We conclude that the young of this subsocial animal increased predation efficiency by cooperative hunting after the mother's death.     

贵阳市“两湖一库”周边蜘蛛体内镉含量及暴露风险

调查了高镉地质背景区蜘蛛(肖蛸科、园蛛科、蟹蛛科和络新妇科)及其生境水体、土壤和植物中的镉含量,探讨了蜘蛛体内镉的来源、影响因子及存在风险。结果表明,研究区蜘蛛体内的平均镉含量为1. 82±1. 37μg/g(n=130),表现为园蛛科肖蛸科络新妇科≈蟹蛛科。蜘蛛体重与体内镉含量表现出弱的负相关关系(r=-0. 17,p=0. 08),暗示了蜘蛛生长发育过程中的生物稀释效应。狩猎型蟹蛛科和结网型园蛛科蜘蛛体内镉含量与对应土壤镉含量呈显著正相关关系(r=0. 61,0. 97),并且它们对土壤的生物富集因子均大于1,表明这两类蜘蛛可以用来指示土壤镉污染。生物有毒物质残留指数显示,研究区蜘蛛受高镉地质背景影响,体内存在着一定的镉暴露风险。     

Quality of Meliponinae honey: Pesticides residues,pollen identity,and microbiological profiles

This study aims at evaluating the quality of honey of Melipona quadrifasciata quadrifasciata Tetragonisca angustula and Scaptotrigona depilis. Pollen analysis was performed to identify the floral resources used for the production of honey, and 19 pollen types were identified. Microbiological analyses identified the presence of coliforms, molds, and yeasts, but Clostridium botulinum was not found. Using the modified “Quick, Easy, Cheap, Effective, Rugged, and Safe” method followed by ultra‐high performance liquid chromatography‐tandem mass spectrometry determination, eight pesticides were detected in the honey of T. angustula and only two in the honey from S. depilis. The honey of M. q. quadrifasciata did not present pesticide residues. The data pointed out the relevance of good practices to avoid the contamination of honey with sources of microbiological contaminants, which may impair the product's safety for human consumption.     

Mercury distribution and bioaccumulation up the soil-plant-grasshopper-spider food chain in Huludao City, China

The purpose of this study is to investigate total mercury (THg) distribution and its bioaccumulation up the soil-plant-grasshopperspider in the Huludao City, which is polluted seriously by chlor-alkali and zinc smelting industry in Northeast of China. Results indicated that average THg concentrations in soil, plant leaves, grasshopper Locusta migratoria manilensis and Acrida chinensis, and spider were 0.151, 0.119, 0.167 and 0.134 mg/kg, respectively. THg spatial distribution suggested that most of mercury came from the chlor-alkali plant and the two zinc smelteries. The highest mercury concentration was found in the wings among different grasshoppers’ organs. Although spiders are the predatory, THg concentrations in their bodies were not high, and only on the same level as in grasshoppers, which might be due to spiders’ special living habits. In the light of the mercury transportation at every stage of the soil-plant-grasshopper-spider food chain, the bioaccumulation factors were 0.03, 0.79–1.11 and 0.80–1.13 respectively. It suggested that mercury biomagnification up terrestrial food chains was not so large and obvious as it was in the aquatic food chain.     

Worker allocation in insect societies: coordination of nectar foragers and nectar receivers in honey bee (Apis mellifera) colonies

Nectar collection in the honey-bee is partitioned. Foragers collect nectar and take it to the nest, where they transfer it to receiver bees who then store it in cells. Because nectar is a fluctuating and unpredictable resource, changes in worker allocation are required to balance the work capacities of foragers and receivers so that the resource is exploited efficiently. Honey bee colonies use a complex system of signals and other feedback mechanisms to coordinate the relative and total work capacities of the two groups of workers involved. We present a functional evaluation of each of the component mechanisms used by honey bees – waggle dance, tremble dance, stop signal, shaking signal and abandonment – and analyse how their interplay leads to group-level regulation. We contrast the actual regulatory system of the honey bee with theory. The tremble dance conforms to predicted best use of information, where the group in excess applies negative feedback to itself and positive feedback to the group in shortage, but this is not true of the waggle dance. Reasons for this and other discrepancies are discussed. We also suggest reasons why honey bees use a combination of recruitment plus abandonment and not switching between subtasks, which is another mechanism for balancing the work capacities of foragers and receivers. We propose that the waggle and tremble dances are the primary regulation mechanisms, and that the stop and shaking signals are secondary mechanisms, which fine-tune the system. Fine-tuning is needed because of the inherent unreliability of the cues, queueing delays, which foragers use to make recruitment decisions. Received: 15 December 1998 / Received in revised form: 6 March 1999 / Accepted: 12 March 1999