不同水平亮氨酸对繁殖期意大利蜜蜂蜂群群势及工蜂发育的影响

【目的】评价日粮中不同水平亮氨酸对繁殖期意大利蜜蜂Apis mellifera ligustica蜂群群势及工蜂发育的影响。【方法】选取重庆荣昌本地繁殖期意大利蜜蜂21群,随机分为7组,分别饲喂添加0,15.30,17.50,26.25,35.00,43.75和52.5 g/kg亮氨酸的试验日粮,每12 d测定各组蜂群群势、封盖子量、蜂群取食量和营造王台情况,24 d后测定蜂群采集行为、工蜂初生重、工蜂虫体蛋白质含量及工蜂寿命。【结果】当亮氨酸添加水平为43.75和52.50 g/kg时能够显著提高繁殖期意大利蜜蜂的蜂群群势、封盖子量、蜂群取食量及采集行为(P0.05)。与空白对照组相比,基础日粮组及各亮氨酸添加组的新出房蜂和6日龄幼虫体蛋白质含量较高(P0.05);各亮氨酸添加组的工蜂初生重显著高于空白组(P0.05);不同亮氨酸添加水平对意大利蜜蜂工蜂寿命影响较小。此外,亮氨酸添加水平26.25,35.00和43.75 g/kg能够在饲喂0-24 d时促进蜂群营造自然王台,刺激蜂群分蜂。【结论】配方日粮中43.75和52.5 g/kg的亮氨酸能够显著促进繁殖期意大利蜜蜂蜂群发展,其中43.75 g/kg的亮氨酸饲喂量还能刺激蜂群营造自然王台,激发蜂群分蜂。     

蜜蜂群内生殖分工体系的形成及其维持

本文对蜜蜂群内生殖分工体系的形成及其维持机制进行综述。蜜蜂群体具有完善的劳动分工(包括生殖分工)体系,蜂王垄断生殖权力,而工蜂生殖器官发育不完全,在蜂王信息素和幼虫信息素的作用下产卵受到抑制。蜂王的多雄交配机制降低了群内个体间的亲缘关系,但也促进了工蜂间相互监督机制的形成。工蜂间的相互监督,结合蜂王和幼虫信息素对工蜂卵巢发育的影响,解决了蜂王与工蜂、工蜂与工蜂间的生殖利益冲突,保障了蜂群内的生殖分工体系,提高了群体效率,维护了蜂群的真社会性。     

幼虫信息素中三种酯类对中华蜜蜂工蜂发育和采集行为的影响

为研究中华蜜蜂Apis cerana cerana幼虫信息素中的3种酯类成分(甲基棕榈酸酯、乙基棕榈酸酯和乙基油酸酯)对其工蜂发育和采集行为的影响, 取1日龄工蜂喂食不同食物, 把喂食食物(炼糖)中添加0.1%或1%(w/w)某种酯类的工蜂组作为处理组, 以喂食食物(炼糖)中不添加酯类(0%)的工蜂组作为对照组, 然后测定7日龄、14日龄工蜂的卵巢发育和3, 5, 7, 12, 18和21日龄工蜂王浆腺的宽度, 以及工蜂首次参加采集的日龄。结果表明: (1)在无王群中, 甲基棕榈酸酯两处理组(1%, 0.1%)的7日龄和14日龄工蜂卵巢发育率都显著低于对照组; 在无王群中, 0.1%乙基棕榈酸酯处理组的14日龄工蜂卵巢发育率极显著低于对照组; 在有王群中, 1%甲基棕榈酸酯处理组和乙基油酸酯两处理组的14日龄工蜂卵巢发育都显著低于对照组;(2)在有王群中, 甲基棕榈酸酯两处理组的5日龄和7日龄工蜂王浆腺宽度显著大于对照组, 12, 18, 21日龄工蜂王浆腺宽度极显著小于对照组; 乙基油酸酯两处理组的7~21日龄工蜂王浆腺宽度显著小于对照组;(3)3种酯类, 只有甲基棕榈酸酯处理组的工蜂首次采集日龄显著大于对照组。这些结果说明, 不同蜜蜂幼虫信息素对中华蜜蜂工蜂发育和采集行为具有不同的生物学效应。     

中华蜜蜂急造王台的工蜂亲属优惠

人为使3群中华蜜蜂(Apis cerana cerana)失王而出现急造王台后,应用3个蜜蜂微卫星位点A14、A107和B124对蜂群、急造王台中的幼虫及其哺育蜂的亚家庭进行鉴别,以此来研究中华蜜蜂急造王台的工蜂亲属优惠.结果显示:在3个实验蜂群Ⅰ、Ⅱ、Ⅲ中分别检测到11、13和14个亚家庭,各蜂群各亚家庭之间的工蜂分布差异不显著.然而各蜂群中急造王台却分别只出现在少数的3、4和5个亚家庭中,各亚家庭之间在王台出现率上存在极显著的差异.另外,各急造王台的所有哺育蜂并非只来自幼虫所在的亚家庭,而是分布在更多的亚家庭里,并且各亚家庭之间差异不显著.以上结果证明:中华蜜蜂急造王台时,在蜂王幼虫的选择过程中存在工蜂亲属优惠行为,但蜂王幼虫与它们的哺育工蜂之间并不存在工蜂亲属优惠     

西方蜜蜂工蜂蛹响应低温胁迫的差异表达基因分析

【目的】本研究旨在从转录组水平筛选和分析西方蜜蜂Apis mellifera工蜂不同时期蛹对低温胁迫反应的差异表达基因(DEGs)。【方法】将西方蜜蜂工蜂封盖后3 d预蛹以及封盖后6和9 d蛹分别置于低温环境(20℃)和最适发育温度(35℃)中4 h,分别作为处理组和对照组,通过转录组学技术筛选低温处理组与对应的对照组之间的DEGs,并进行GO功能分类和KEGG通路分析。利用RT qPCR分别对封盖后3 d预蛹以及封盖后6和9 d蛹的8, 6和5个DEGs的表达谱进行验证。【结果】与对照组相比,封盖后3 d预蛹以及封盖后6和9 d蛹受低温胁迫后的DEGs分别有220, 50和26个;GO功能分类发现,DEGs富集数最多的条目为代谢进程、细胞进程、催化活性和结合,封盖后3 d预蛹的DEGs在生物学进程调控、细胞部分和细胞器等有较多富集。KEGG通路分析显示,处理组和对照组间西方蜜蜂各日龄DEGs在整体概述图、氨基酸代谢、信号转导、运输和分解代谢有富集。封盖后3 d预蛹以及封盖后6和9 d蛹受低温胁迫后共有的DEG 3-磷酸肌醇依赖性蛋白激酶1基因PDK1上调表达,同时富集在自噬-动物、mTOR和FoxO信号通路。低温胁迫后,封盖后3 d预蛹的胰岛素受体底物1-B基因IRS1-B和Kruppel同源物1基因Kr-h1上调表达,而核激素受体FTZ-F1基因Ftz-F1与蜕皮启动激素基因Eth显著下调表达,说明封盖后3 d预蛹响应低温细胞自噬和蜕皮受到抑制程度更大。在低温胁迫后封盖后6 d蛹中与昆虫角质层着色与免疫相关的酪氨酸羟化酶基因TyHyd下调表达;与对照组相比,在低温胁迫后封盖后9 d蛹中DEGs最少,说明在3个蛹期中,其受低温的影响较小。【结论】本研究测定了西方蜜蜂3个不同发育阶段蛹响应低温的DEGs,结果显示大部分DEGs为阶段特有,说明西方蜜蜂不同发育阶段响应低温的机制不同。一些共有DEGs以及阶段特有DEGs的功能研究和其作用机制是进一步研究蜜蜂对低温响应机制的重点内容,为探究蜜蜂蛹期响应低温胁迫的分子机制提供了基础数据。     

蜜蜂无政府主义蜂群的研究进展

西方蜜蜂Apis mellifera作为典型的社会性昆虫, 最重要的特征是生殖劳动分工。蜂王垄断蜂群的生殖权利, 工蜂生殖功能受到抑制, 从事除产卵和交配以外的所有职能。而在无政府主义蜂群中, 即使蜂王存在, 也有较多工蜂的卵巢激活并产卵, 蜂群中大多数雄蜂是工蜂的后代。这些特殊蜂群为正常蜂群工蜂不育机制研究提供了绝佳的反例材料。本文对无政府主义蜂群的行为特征、 产生条件、 遗传基础等研究进行了综述。无政府主义蜂群中有较多的工蜂产卵, 且工蜂所产卵能够逃避工蜂监督, 这种行为的产生受环境、 遗传组成、 基因表达等多种因素的影响, 并且遗传结构体系复杂, 参与调控的基因数量多。无政府主义蜂群行为机制的研究为工蜂不育机制的揭示及其他社会性昆虫工职不育基因的筛选和功能研究提供借鉴。     

Cloning and expression profiling of the DNA methyltransferase Dnmt3 gene in the Chinese honeybee, Apis cerana cerana (Hymenoptera:Apidae )

为探究中华蜜蜂Apis cerana cerana的DNA甲基化模式,本研究采用RT-PCR技术克隆了中华蜜蜂DNA甲基化转移酶3( Dnmt3)基因(GenBank登录号为JQ740768);采用荧光定量PCR检测不同发育时期工蜂(4日龄蛹,1,7和30日龄成年蜂及产卵工蜂)和蜂王(4日龄蛹,1日龄蜂王和产卵蜂王)头部的Dnmt3基因mRNA的表达量.结果表明:该基因cDNA序列全长2 277 bp,编码758个氨基酸残基,预测的蛋白分子量为88.24 kD,等电点为7.85.将中华蜜蜂与其他物种的Dnmt3基因的结构域进行比对,同时将该基因推导的氨基酸序列与其他物种的Dnmt3氨基酸序列进行同源性比对和系统发育分析,发现与西方蜜蜂的Dnmt3序列一致性高达99％.该基因在工蜂和蜂王不同发育时期均有表达,1日龄工蜂与7日龄工蜂中没有显著差异(P＞0.05),30日龄工蜂中的表达量显著高于前两者(P＜0.05);蜂王蛹中的表达量显著高于工蜂蛹(P＜0.05);1日龄的蜂王中的表达量显著高于1日龄的工蜂(P＜0.05);产卵工蜂与产卵蜂王中的表达量没有差异(P＞0.05).这种表达情况提示其可能与工蜂劳动分工及蜜蜂卵巢发育有关.     

幼虫信息素中三种酯类对中华蜜蜂和意大利蜜蜂工蜂哺育和封盖行为以及蜂王发育影响

为研究蜜蜂幼虫信息素中3种酯类成分（甲基棕榈酸酯、乙基棕榈酸酯和乙基油酸酯）对中华蜜蜂Apis cerana cerana和意大利蜜蜂Apis mellifera ligustica工蜂哺育行为、封盖行为以及蜂王发育影响, 在人造蜂蜡王台中加入1%和0.1%（w/w）的3种酯类作为实验组, 以不添加酯类（0%）的为对照组, 移入1日龄工蜂幼虫, 测定王台接受率、单个王台中幼虫和王浆重量; 另将分别添加1%和0.1%（w/w）3种酯类的石蜡假幼虫放入工蜂巢房中, 同样设对照组, 测定假幼虫的封盖率; 在新鲜王浆中以1%和0.1%（w/w）分别加入3种酯类作为实验组, 以不添加酯类（0%）的作为对照组, 再分别在1日龄、2日龄和3日龄幼虫王台中加入0.01 mL含有酯类的蜂王浆, 并测定蜂王初生重和卵巢管数量。结果表明: 0.1%甲基棕榈酸酯可以显著提高中蜂和意蜂幼虫重量; 意蜂的甲基棕榈酸酯和乙基油酸酯两个实验组(1.0%, 0.1%)假幼虫封盖率都极显著高于对照组; 乙基油酸酯两个实验组(1.0%, 0.1%)都显著降低了中蜂和意蜂蜂王初生重和卵巢管数量。这说明不同蜜蜂幼虫信息素具有不同的生物学效应。     

地熊蜂蜂群发育性状评价及其饲料花粉配比优化

【目的】为了明确熊蜂蜂群发育过程中具有代表性的性状指标及其饲料花粉最优配比。【方法】以山杏Armeniaca sibirica花粉、山柳Salix caprea花粉和油菜Brassica rapa花粉为原料,通过{3,3}混料设计得到7种配比的混合花粉,分析不同混合花粉对地熊蜂Bombus terrestris(L.)无王工蜂群的产卵前时间、幼虫拖出数、幼虫总数量、幼虫总重量、蛹总数量、蛹总重量、雄蜂出房时间、出房雄蜂数量和雄蜂出生重9个蜂群性状指标的影响,使用主成分分析对蜂群性状指标进行综合评价,并通过混料回归模型预测熊蜂蜂群饲养过程中的最优花粉配比。【结果】地熊蜂无王工蜂群发育过程的9个性状指标可以归纳为幼虫发育、蛹发育、成蜂发育、蜂群发育周期4类评价因子,其中幼虫总数量、蛹总重量、雄蜂出生重、产卵前时间和雄蜂出房时间是5个主要性状指标;以蜂群主要性状指标为评价依据,得出蜂群饲养过程中最优花粉配比:当以油菜花粉单独饲喂蜂群时蜂群产卵前时间短、幼虫总数量最多、蛹总重量最大,当山杏花粉、山柳花粉和油菜花粉以1︰1.5︰1.5比例饲喂蜂群时雄蜂出房时间最短,当山柳花粉和油菜花粉以3︰1比例饲喂蜂群时雄蜂出生重最大。【结论】明确了地熊蜂无王工蜂群发育过程中的重要性状指标和饲料花粉最优配比,为进一步研究商品化熊蜂群不同发育阶段的营养需求奠定了基础。     

发育温度对蜜蜂归巢能力及记忆相关基因表达的影响

【目的】本试验旨在研究不同发育温度对意大利蜜蜂Apis mellifera ligustica工蜂归巢能力及学习记忆相关基因表达的影响。【方法】选择3群群势一致的意大利蜜蜂,控制蜂王在一张经工蜂清理的工蜂巢脾中产卵48 h,之后移至孵化区。子脾即将封盖时,平均分成3块,分别放入33℃(Ⅰ组)、35℃(Ⅱ组)、37℃(Ⅲ组)的恒温恒湿箱中继续发育(相对湿度为75%±5%),每群为1个重复。工蜂羽化出房时,用不同颜色标记不同发育温度下羽化的工蜂,并放回原蜂王产卵群,测定其采集时期在1 000 m、2 000 m的回归率及不同日龄(刚出房,10日龄,20日龄)工蜂3个记忆相关基因[谷氨酸受体A型基因(Glu-RA)、N-甲基-D-天冬氨酸受体1型基因(Nmdar1)、酪氨酸受体1型基因(tyr1)]的表达情况。【结果】结果表明:试验Ⅱ组和试验Ⅲ组发育的采集蜂在1 000 m和2 000 m处的回归率均显著高于Ⅰ组,但试验Ⅱ组与试验Ⅲ组之间差异不显著;试验Ⅱ组和Ⅲ组刚出房工蜂、10日龄工蜂和20日龄工蜂的Glu RA和Nmdar1基因相对表达量显著高于试验Ⅰ组,但试验Ⅱ组与Ⅲ组之间差异不显著;试验Ⅱ组刚出房工蜂的Tyr1基因相对表达量显著高于试验Ⅰ组与Ⅲ组,但试验Ⅰ组与试验Ⅲ组之间差异不显著,另外,各试验组10日龄和20日龄工蜂Tyr1基因相对表达量差异均不显著。【结论】过低发育温度会影响蜜蜂的归巢能力和记忆相关基因的表达。     

中蜂与意蜂无王群培育非自身蜂种蜂子及改造王台特性

以中华蜜蜂和意大利蜜蜂为试验材料,通过组织相应无王群,把一蜂种无王群中的子脾加入到另一蜂种无王群中,进行中蜂和意蜂无王群培育非自身蜂种蜂子和改造王台特性研究,当未培育出蜂王时,分别从原有王群中调入子脾进行第2、第3期试验。结果表明:中蜂无王群中的工蜂会清除引入意蜂子脾中的蜂卵,但随着引入意蜂子脾封盖子羽化出房的意蜂幼蜂数量增加而逐渐接受意蜂幼虫,蜂群未改造意蜂王台,只培育出中蜂蜂王;意蜂无王群中的工蜂会随着引入中蜂子脾中羽化出房的中蜂幼蜂数量增加而逐渐接受中蜂卵及幼虫,并从第2期试验开始会改造中蜂王台,但最终只培育出意蜂蜂王。     

Effects of social conditions on Juvenile Hormone mediated reproductive development in Bombus terrestris workers

Abstract. During the annual life cycle of the bumble bee Bombus terrestris (L.) colony, there is a stage characterized by worker reproduction in the presence of the queen. It has been proposed that this is a result of a decrease in queen inhibition. This hypothesis was examined by studying the effects of queens taken from colonies at different stages of development on several aspects of worker physiology and behaviour: rates of Juvenile Hormone (JH) release in vitro , ovary development, and behaviour associated with reproduction. After optimizing and validating the radiochemical assay for JH release for bumble bee workers, we found that queenless workers had significantly more developed ovaries and higher rates of release of JH than did queenright workers, confirming and extending previous findings that suggest that bumblebee ovarian development is under JH control. Mated queens, separated from their colony and brood, can have the same inhibitory effect on the reproductive development of callow workers. In contrast, workers confined with virgin queens or in queenless groups demonstrated a significantly higher rate of release of JH, overt aggression and threatening behaviours. However, there were no differences in rates of release of JH between workers confined in groups in the laboratory with queens taken from colonies either before or after the onset of worker reproduction. Furthermore, overt aggression and threatening behaviours were similar and low in both types of groups. These results gave no support to the hypothesis that a decrease in queen inhibition is associated with the onset of worker reproduction. We also show that young workers reared in colonies either before or after worker reproduction occurs, or in queenless colonies, all demonstrated similar, low rates of release of JH. These results suggest that older workers may inhibit the corpora allata of younger workers in queenless colonies.     

Colony strength and queen replacement in Melipona marginata (Apidae: Meliponini).

Physogastric queens of Melipona marginata were removed from their colonies in order to verify the acceptance of a new queen by workers. Colony strength was evaluated according to queen oviposition rate and comb diameters. Replacement was observed seven times. Its occurrence and speed related positively to colony strength, independently of queen's age. In weak colonies, queen replacement was observed only once, following colony population increase that occurred after introduction of combs from another colony. Worker oviposition after queen removal was observed three times: in a strong colony with virgin queens and males, and in two of the weak colonies. In the first two or three days of new queen oviposition, during which most of the eggs were eaten by the queen, worker oviposition preceded almost all provisioning and oviposition processes (POPs). After this period, worker oviposition decreased until it reached around 25% of the POPs. Daily oviposition rate of young queens decreased or was even interrupted by hatching of their first brood.     

Worker laying in leafcutter ant Acromyrmex subterraneus brunneus （Formicidae, Attini）

We studied the process of offspring production in queenless colonies of Acromyrmex subterraneus brunneus, and particularly evaluated the ovary development of workers as a function of their age. For this, subcolonies were set up and evaluated at different periods of isolation from the queen （2, 4 and 6 months）, besides individually labeled age groups. The subcolonies were assessed according to offspring production and ovaries containing oocytes or not. The evaluations showed worker oviposition and development of males originating from worker-laid eggs. At 2 months＇ absence of the queen, eggs and larvae were found, with eggs in a higher proportion than larvae. After 4 months, the proportion of eggs had reduced while larvae had increased, and a pupa was found in one subcolony. At 6 months, besides a higher share of larvae, one pupa and one adult male were found. Dissection of workers revealed ovaries containing oocytes during the periods of evaluation. Only a group of medium-sized and large workers, 23.3%, 20.9% and 37.5% of the population from each period assessed in queenless subcolonies respectively, presented developed oocytes in the ovary. The same was observed in colonies with a queen, with 17.6%, 19.6% and 7.8% of the group of dissected workers from each time period, respectively. With respect to worker age, we observed by dissection of the ovary, that the greatest percentage of individuals with ovarioles containing oocytes occurred at 45 days （6 weeks） up to 90 days （12 weeks）. These results probably are associated with the workers reproduction and the laying of trophic and reproductive eggs in colonies with and without a queen; these eggs have distinct functions in each situation.     

Effect of queen excluders on ovary activation in workers of the Eastern honeybee Apis cerana

Honeybee workers generally refrain from personal reproduction when a queen is present. Workers discern the presence and fecundity of the queen via volatile pheromones that permeate throughout the colony. Pheromones are emitted both by the queen herself and by the brood that she produces. If pheromone production is disrupted, some workers initiate egg laying. The Eastern honeybee Apis cerana is unusual in that workers have high levels of ovary activation even in the presence of a queen. To investigate the effect of disruption to pheromone dispersal, we fitted three A. cerana colonies with vertical queen excluders, thus splitting the colonies into a half containing a queen and a half without a queen. We regularly sampled adult workers from both sides of the excluder for 3 weeks. We also sampled workers from three control colonies that did not contain excluders. We found a significant increase in worker ovary activation 3 days after addition of excluders, suggesting that the reduced dispersal of pheromones allowed some workers to become reproductively active. Workers attempted to rear queen cells on the queenless halves of all three colonies. Queen-rearing ceased on day 9, at which time no queen-laid brood remained on the queenless halves of the colonies. Ovary activation rates continued to climb until day 9 and then gradually began to decline. With the exception of one egg, we did not observe worker-laid brood on the queenless side of the colonies, suggesting that workers continued policing eggs laid by workers. We conclude that if the distribution of brood pheromone is impeded, workers prepare to supersede their queen, accompanied by high levels of worker ovary activation. However, because workers continue to police each other, high ovary activation does not result in worker-produced drones.     

It's good to be queen: classically eusocial colony structure and low worker fitness in an obligately social sweat bee

Lasioglossum malachurum, a bee species common across much of Europe, is obligately eusocial across its range but exhibits clear geographic variation in demography and social behaviour. This variation suggests that social interactions between queens and workers, opportunities for worker oviposition, and patterns of relatedness among nest mates may vary considerably, both within and among regions. In this study, we used three microsatellite loci with 12-18 alleles each to examine the sociogenetic structure of colonies from a population at Agios Nikolaos Monemvasias in southern Greece. These analyses reveal that the majority of colonies exhibit classical eusocial colony structure in which a single queen mated to a single male monopolizes oviposition. Nevertheless, we also detect low rates of multiqueen nest founding, occasional caste switching by worker-destined females, and worker oviposition of both gyne and male-producing eggs in the final brood. Previous evidence that the majority of workers show some ovarian development and a minority (17%) have at least one large oocyte contrasts with the observation that only 2-3% of gynes and males (the so-called reproductive brood) are produced by workers. An evaluation of the parameters of Hamilton's Rule suggests that queens benefit greatly from the help provided by workers but that workers achieve greater fitness by provisioning and laying their own eggs rather than by tending to the queen's eggs. This conflict of interest between the queen and her workers suggests that the discrepancy between potential and achieved worker oviposition is due to queen interference. Comparison of relatedness and maternity patterns in the Agios Nikolaos Monemvasias population with those from a northern population near Tübingen, Germany, points to a north-south cline of increasingly effective queen control of worker behaviour.     

Queen pheromones affecting the production of queen-like secretion in workers

The honeybee queen pheromones promote both worker sterility and worker-like pheromone composition; in their absence workers become fertile and express the queen pheromones. Which of the queen pheromones regulate worker pheromone expression and how, is still elusive. Here we investigated how two queen pheromones, the mandibular and Dufour’s, singly or combined, affect worker ovarian activation and occurrence of queen-like Dufour’s esters. Although queen mandibular pheromone (QMP) alone, or combined with Dufour’s secretion, inhibited to some extent worker reproduction, neither was as effective as the queen. The effect of the queen pheromones on worker pheromone expression was limited to workers with developed ovaries. Here too, QMP and Dufour’s combined had the greatest inhibitory effect. In contrast, treatment with Dufour’s alone resulted in augmentation of esters in the workers. This is another demonstration that a pheromone emitted by one individual affects the rates of its production in another individual. Ester production was tightly coupled to ovarian development. However fertile workers from queenright or QMP-treated colonies had significantly higher amounts of esters in their Dufour’s gland than untreated queenless colonies. The fact that the queen or QMP exert greater suppression on signal production than on ovary activation, suggests disparate regulatory pathways, and presents a challenging ultimate as well as proximate questions.     

Egg marking pheromones of anarchistic worker honeybees (Apis mellifera)

In honeybees, worker policing via egg eating enforces functionalworker sterility in colonies with a queen and brood. It is thoughtthat queens mark their eggs with a chemical signal, indicatingthat their eggs are queen-laid. Worker-laid eggs lack this signaland are, therefore, eaten by policing workers. Anarchistic workerhoneybees have been hypothesized to circumvent worker policingby mimicking the queen egg-marking signal. We investigated thisphenomenon by relating chemical profiles of workers and theireggs to egg acceptability. We found that the ability of someworkers (anarchistic workers in queenright colonies and deviantworkers from a queenless colony) to lay more acceptable eggsis due to them producing significant amounts of queen-like estersfrom their Dufour's gland. These esters appear to be transferredto eggs during laying and increase egg survival. However, theseesters cannot be the normal queen egg-marking signal, as theyare generally absent from queen-laid eggs and only increasethe short-term persistence of worker-laid eggs, because only7–30% of anarchistic worker-laid eggs persisted to hatchingversus 91–92% of queen-laid eggs. All workers can producesome esters, but only workers that greatly increase their esterproduction lay more acceptable eggs. The production of estersappears to be a flexible response, as anarchistic workers rearedin queenless colonies did not increase their ester production,while some deviant workers in queenless colonies did increasetheir ester production.     

Social behavior and brood decline in reproductive-phase colonies ofBelonogaster petiolata (Degeer) (Hymenoptera: Vespidae)

Colonies ofBelonogaster petiolata in Gauteng (South Africa) produced reproductive offspring (gynes and males) in late January and early February of each nesting season; their appearance was associated with a decline in worker and brood numbers. Brood decline could commence in the presence of a dominant, reproductively active queen, and loss or removal of the queen was not followed directly by cessation of nest growth and brood care. An older worker usually took over the α-position in queenless colonies. Several factors appear to contribute to brood decline and, ultimately, termination of the colony cycle in this species. These include (1) cessation of the supply of solid food to colonies (and particularly their larvae) during the reproductive phase, (2) a decrease in the worker/larva ratio during the latter phase due to the progressive loss of workers, (3) increasing number of gynes and males, and (4) an adult priority over food reception from foragers.     

Parasites delay worker reproduction in bumblebees: consequences for eusociality

Workers in eusocial insects usually tend the brood of the queenand so achieve representation in the next generation throughaiding relatives to reproduce. However, workers of some eusocialspecies, such as bumblebees, are capable of reproductive activityeven in the presence of the queen (in queen-right colonies),and worker reproduction is associated with aggressive behaviorsand egg cannibalism, both of which reduce colony efficiency.Thus, factors that affect worker ovariandevelopment, a preconditionfor reproduction, can influence social harmony and colony productivity.Parasites are a ubiquitous and important part of the bioticenvironment of all organisms. Here we show that parasites playan important role in the reproductive physiology of worker bumblebeesin queen-right colonies of Bombus terrestris, affecting thepattern and timing of ovarian development and oviposition. Workersfrom colonies parasitized with the intestinal trypanosome Crithidiabombi had less developed ovaries than workers of the same agefrom unparasitized colonies. In addition, parasitized colonieswere smaller than unparasitized colonies for about the firsthalf of colony development. This generated further demographiceffects such that workers were on average younger in parasitizedthan in unparasitized colonies around the time of the onsetof worker oviposition, and worker oviposition occurred significantlylater in parasitized colonies. Workers in parasitized coloniestherefore had lower individual reproductive potential and werecooperative for a larger proportion of the colony cycle thanthose in unparasitized colonies. In this system, where transmissionof the parasite between years probably occurs only in infested,young queens, this effect may represent an adaptation on thepart of the parasite to ensure its successful passage throughthe winter. Parasites, by reducing the cost of worker cooperation,may facilitate queen control over her worker force and playan important role in moderating the social organization of eusocialinsect colonies.