Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

1. Predation‐exclusion experiments have highlighted that top‐down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. 2. We conducted 1‐year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. 3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant‐excluded than in control trees, whereas only dermapterans were more abundant in bird‐excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. 4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator–prey system.     

Negative association between parental care and sibling cooperation in earwigs: a new perspective on the early evolution of family life?

The evolution of family life requires net fitness benefits for offspring, which are commonly assumed to mainly derive from parental care. However, an additional source of benefits for offspring is often overlooked: cooperative interactions among juvenile siblings. In this study, we examined how sibling cooperation and parental care could jointly contribute to the early evolution of family life. Specifically, we tested whether the level of food transferred among siblings (sibling cooperation) in the European earwig Forficula auricularia (1) depends on the level of maternal food provisioning (parental care) and (2) is translated into offspring survival, as well as female investment into future reproduction. We show that higher levels of sibling food transfer were associated with lower levels of maternal food provisioning, possibly reflecting a compensatory relationship between sibling cooperation and maternal care. Furthermore, the level of sibling food transfer did not influence offspring survival, but was associated with negative effects on the production of the second and terminal clutch by the tending mothers. These findings indicate that sibling cooperation could mitigate the detrimental effects on offspring survival that result from being tended by low‐quality mothers. More generally, they are in line with the hypothesis that sibling cooperation is an ancestral behaviour that can be retained to compensate for insufficient levels of parental investment.     

Abundance and natural control of the woolly aphid <Emphasis Type="Italic">Eriosoma lanigerum</Emphasis> in an Australian apple orchard IPM program

Woolly aphid (Eriosoma lanigerum Hausmann) (Hemiptera: Aphididae), was monitored over three growing seasons (1995--1998) to assess its abundance and management under apple IPM programs at Bathurst on the Central Tablelands of NSW, Australia. Woolly aphid infestations were found to be extremely low in IPM programs utilising mating disruption and fenoxycarb for codling moth Cydia pomonella L. (Lepidoptera: Tortricidae) control. This was the direct result of increased numbers of natural enemies. No insecticides were applied for woolly aphid control. Under the IPM strategies tested the principal control agent was identified as European earwig (Forficula auricularia L.) (Dermaptera: Forficulidae). Earwigs in combination with Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) reduced woolly aphid infestations below the action threshold set by commercial growers. However, A. mali together with other flying natural enemies, e.g., ladybirds, lacewings and hoverflies, did not provide commercially acceptable control of woolly aphid in the absence of earwigs. Under the conventional spray program, using the broad-spectrum insecticide azinphos-methyl for codling moth control, the level of woolly aphid infestation increased with each successive season and biological control was not established. When azinphos-methyl was withdrawn, natural enemies migrated in and provided control of woolly aphid within one season. This is the first study to show that the biological control of woolly aphid can be achieved in a commercially viable IPM program.     

THE ONTOGENY OF ASYMMETRY IN EARWIG FORCEPS

Fluctuating asymmetry may play an important role in the evolution of naturally selected and secondary sexual traits. However, very little is known about how asymmetries arise or how organisms maintain symmetry during development. Here I propose three mutually exclusive patterns for the development of asymmetries through consecutive growth stages: (1) compensatory growth, in which growth of the shorter side is greatest at the following growth stage; (2) persistent growth, in which growth of the longer side is greatest at the following growth stage; and (3) uncorrelated growth in which growth of the following stage is unrelated to the asymmetry at the previous one. I followed the growth in the forceps of male earwigs through four successive instars. Dyar's rule was used as a null model of insect growth. In the molt from the second to third instar, asymmetries increased through uncorrelated growth and with the magnitude but not the sign expected from Dyar's rule. However, following this, at the molts between instars 3–4 and 4–5, compensatory growth maintained asymmetries at a lower level than expected from Dyar's rule. Although there was no reduction in the absolute magnitude of asymmetry, relative asymmetry did decline. The net growth of forceps length did not follow Dyar's rule. The interpretation of patterns of growth were more sensitive and informative than the interpretation of the relations between asymmetries at consecutive instars.     

Anterior neural centres in echinoderm bipinnaria and auricularia larvae: cell types and organization

Serial and interval electron micrograph series were used to examine the anterior part of the ciliary band system in the bipinnaria larva of Pisaster ochraceus and the auricularia larva of Stichopus californicus for evidence of ganglion‐like organization. The bipinnaria has paired concentrations of Multipolar with Apical Processes (MAP) cells in this region that correspond in position with previously identified clusters of serotonergic and peptidergic neurones. MAP cells located in the centre of the band have well‐developed apical processes, but no cilium. Those at the sides of the band have fewer processes, but some have recumbent cilia that extend under the glycocalyx, suggesting a sensory function. Comparable cell types are not found elsewhere in the band, a clear indication that the apical parts of the ciliary band system are organized in a distinctive fashion. Two neuronal cell types were identified in the apical region of the auricularia larva, a conventional bipolar neurone that corresponds with previously described serotonergic apical cells, and more numerous MAP cells for which there is no previous record and hence, no known transmitter. Previous immunocytochemical studies are summarized and re‐examined in the light of these results. Relevant evolutionary issues are also discussed, but the data fail to provide strong evidence either for or against Garstang’s hypothesis that the chordate brain and spinal cord derive from larval ciliary bands resembling those of modern echinoderms.     

A chemical signal of offspring quality affects maternal care in a social insect

Begging signals of offspring are condition-dependent cues that are usually predicted to display information about the short-term need (i.e. hunger) to which parents respond by allocating more food. However, recent models and experiments have revealed that parents, depending on the species and context, may respond to signals of quality (i.e. offspring reproductive value) rather than need. Despite the critical importance of this distinction for life history and conflict resolution theory, there is still limited knowledge of alternative functions of offspring signals. In this study, we investigated the communication between offspring and caring females of the common earwig, Forficula auricularia, hypothesizing that offspring chemical cues display information about nutritional condition to which females respond in terms of maternal food provisioning. Consistent with the prediction for a signal of quality we found that mothers exposed to chemical cues from well-fed nymphs foraged significantly more and allocated food to more nymphs compared with females exposed to solvent (control) or chemical cues from poorly fed nymphs. Chemical analysis revealed significant differences in the relative quantities of specific cuticular hydrocarbon compounds between treatments. To our knowledge, this study demonstrates for the first time that an offspring chemical signal reflects nutritional quality and influences maternal care.     

Soil contact toxicity of insecticides to the european earwigForficula auricularia [Dermaptera]

The soil contact effects of several commonly used agricultural insecticides on 2nd instar and adultForficula auricularia (L.) were studied in the laboratory. The earwigs were individually confined on soil surfaces sprayed under a track sprayer. Pirimicarb had no effect on either adult or 2nd instar earwigs. The LD_50,s of 2nd instar earwigs for γ HCH, fenitrothion, DDT and dimethoate were all lower than their normal field rates. Second instars were more susceptible to dimethoate and cypermethrin than adults. The pyrethroids cypermethrin and deltamethrin had LD_50,s above normal field rates. However, high levels of knockdown were induced by both insecticides at concentrations below normal application rates. The effects of this in the field remain unknown.     

欧洲球螋的检疫

北京出入境检验检疫局从美国进境旅客携带的石榴中检出欧洲球螋。了解欧洲球螋的基本特性,能为相关部门对其检疫鉴定提供参考依据。对欧洲球螋的相关文献进行了查阅和整理,详细介绍了欧洲球螋的分类地位、分布、形态特征及近似种等信息,我国出入境检验检疫部门对球螋属的截获情况,讨论了欧洲球螋的检疫意义。认为欧洲球螋在我国无分布且具有一定的入侵风险,口岸应对该虫引起足够的重视。     

欧洲蛷螋雌性对其若虫摄食帮助的研究(英文)

欧洲蛷螋的雌性通过护卵活动可以有效地抑制卵表面霉菌的生长,以保证胚胎的正常发育。但是抚幼行为,特别是接触活动的生物学功能至今尚不明确。本实验表明：幼虫可通过雌虫间接地获取营养物质,从而明显地提高其发育速率和存活率;而单纯的抚幼活动对幼虫的生长和存活并无影响。     

Maternal attendance and the maintenance of family groups in common earwigs (Forficula auricularia): a field experiment

Abstract.  1. Understanding the evolution of subsocial behaviour and parental care requires experimental tests of the functional significance of such behaviours and the role of tending parents in the maintenance of family groups. Studies in subsocial insects addressing these issues experimentally and in the field are still relatively rare.
2. In such a field experiment, it is demonstrated here that the presence of tending females enhances the maintenance of family groups in common earwigs, Forficula auricularia (Dermaptera; Forficulidae). Experimental removal of tending mothers resulted in substantially decreased recovery of occupied nest burrows and larvae. This effect may have been because of decreased survival among experimental larvae, although a possible role for enhanced larval dispersal could not be fully ruled out.
3. Experimental (motherless) larvae were partly observed in family groups with a tending female, in both experimental and control nest burrows, suggesting that these larvae had been adopted by family groups moving to new nest burrows, and/or that experimental larvae may have actively joined other family groups.
4. This study demonstrates under field conditions the functional importance of maternal attendance for the maintenance of family groups in common earwigs, and suggests that adoption and clutch-joining are factors affecting the social structure of this species.