Do Solitary Bees Osmia cornuta Latr. and Osmia lignaria Cresson Use Proximal Visual Cues to Localize Their Nest?

Female Osmia repeatedly return to their nest to provision it with food and building material. The present study investigates the bees' nest localization performance by modifying visual cues in the near-vicinity of the nest. Each of several arrays of nesting holes was surrounded by four geometrical shapes. Removing some or all of the shapes reduced the proportion of direct returns but never prevented a bee from finding the appropriate array and, within that array, its own nest. The more the pattern was modified, the higher was the error score and the longer the delay, but no bee failed finally to find its nest. Shifting the pattern as well as the whole array of holes shifted homing orientation accordingly. There was no effect of the positions of the removed shapes, of contrast inversion, or of modifying the holes array. Our data are discussed in the light of the snapshot theory.     

低温对蝶蛹金小蜂卵成熟及其数量动态的影响

寄生蜂卵成熟动态影响其产卵决策行为,因而对于认识寄生蜂搜寻行为生态学机理具有重要意义。以蝶蛹金小蜂(Pteromalus puparum)-菜粉蝶(Pieris rapae)为模式生物,首先连续3周每隔24 h详细观察子代蜂幼期不同发育阶段的体型、卵巢管以及寄主蛹的外部形态,以此为基础观察了低温处理(模拟越冬温度)被寄生蛹对子代蜂成熟卵数量动态的影响。蝶蛹金小蜂胚后发育历时约2周,其中卵期1 d;幼虫历期约7 d。初孵幼虫体透明;胚后第3—6天体积快速增大,然后减缓,体色由绿变黄;胚后第8天进入预蛹,第9—12天蛹淡色,复眼由淡黄变为深红,第13—14天蛹暗黑色,并逐渐带有金属光泽。卵巢管在羽化当天即开始沉积卵黄,并在羽化后1—4 d连续增加直到出现卵吸收;羽化后5—6 d成熟卵数量增速不明显甚至略有减小。寄主蛹随子代蜂从卵发育至幼虫再到蛹体色从绿色变为灰褐色再到土黄色。低温处理被寄生的寄主蛹(寄生蜂处于老熟幼虫或蛹期)后,羽化成虫的卵巢管略细,成熟卵数量较少。成熟卵数量的变化不仅受低温处理的影响,而且受雌蜂体型大小和日龄的影响;低温处理明显减缓卵成熟速率,各日龄期成熟卵数量均明显减少;适温下成熟卵数量于羽化后第4天达到峰值,而低温处理下成熟卵数量达到峰值的时间延迟至第7天。研究表明,越冬低温对来年羽化的蝶蛹金小蜂卵成熟动态具有不良影响。     

Bethylids attacking stored‐product pests: an overview

Bethylidae is a family belonging to the insect order Hymenoptera and contains about 2 200 described species. Bethylids typically parasitize larvae of Lepidoptera and Coleoptera, including species that are serious pests of stored products. Here, we review the main characteristics of each of the bethylids reported as biological control agent of these pests. The biological characteristics and peculiarities are reported for each species, and the potential for their practical application is discussed.     

Biological characteristics and thermal requirements of a Brazilian strain of the parasitoid Trichogramma pretiosum reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis

A new strain of the parasitoid Trichogramma pretiosum, was collected in Rio Verde County, State of Goiás, Central Brazil, and designated as T. pretiosum RV. This strain was then found to be the most effective one among several different strains of T. pretiosum tested in a parasitoid selection assay. Therefore, its biological characteristics and thermal requirements were studied, aiming at allowing its multiplication under controlled environmental conditions in the laboratory. The parasitoid was reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis at different constant temperatures within an 18–32 °C temperature range. The number of annual generations of the parasitoid was also estimated at those temperatures. Results have shown that T. pretiosum RV developmental time, from egg to adult, was influenced by all temperatures tested within the range, varying from 6.8 to 20.3 days and 6.0 to 17.0 days on eggs of P. includens and A. gemmatalis, respectively. The emergence of T. pretiosum RV from eggs of A. gemmatalis was higher than 94% at all temperatures tested. When this variable was evaluated on eggs of P. includens, however, the figures were higher than that within the 18–30 °C range (more than 98%), and were also statistically higher than the emergence observed at 32 °C (90.2%). The sex ratio of the parasitoids emerged from eggs of A. gemmatalis decreased from 0.55 to 0.29 at 18–32 °C, respectively. However, for those emerged from eggs of P. includens, the sex ratio was similar (0.73, 0.72 and 0.71) at 20, 28 and 32 °C, respectively. The lower temperature threshold (Tb) and thermal constant (K) were 10.65 °C and 151.25 degree-days when the parasitoid was reared on eggs of P. includens; and 11.64 °C and 127.60 degree-days when reared on eggs of A. gemmatalis. The number of generations per month increased from 1.45 to 4.23 and from 1.49 to 4.79 when the parasitoid was reared on eggs of P. includens and A. gemmatalis, respectively, following the increases in the temperature.     

Segregation of temporal and spatial distribution between kleptoparasites and parasitoids of the eusocial sweat bee, Lasioglossum malachurum (Hymenoptera: Halictidae, Mutillidae)

Cuckoo bees and velvet ants use different resources of their shared host bees, the former laying eggs on the host pollen stores and the latter on immature stages. We studied the activity patterns of the cuckoo bee Sphecodes monilicornis and the velvet ant Myrmilla capitata at two nesting sites of their host, the social digger bee Lasioglossum malachurum , over a 3 year period. Due to the difference in host exploitation, we expected different temporal patterns of the two natural enemies as well as a positive spatial association with host nest density for both species. At a daily level, S. monilicornis was more abundant between 10.00 and 15.00 h, while M. capitata was most active in the early morning and late afternoon; both species activities were independent from host provisioning activity. The activity of cuckoo bees was in general positively correlated with the density of open host nests (but not with the total number of nests), while that of velvet ants was rarely correlated with this factor. Sphecodes monilicornis was seen both attacking the guard bees and directly entering into the host nests or digging close to nest entrances, while M. capitata only gained access to host nests through digging. We conclude that the temporal and spatial segregation between the two species may be, at least partially, explained both by the different resources exploited and by the different dynamics of host interactions.     

宁波地区斜纹夜蛾幼虫寄生蜂调查研究

2007—2008年的6～11月对宁波地区重要害虫斜纹夜蛾的寄生性天敌进行了调查,发现寄生蜂有18种,主要种类有：马尼拉陡胸茧蜂Snellenius manilae、侧沟茧蜂Microplitis sp、棉铃虫齿唇姬蜂Carnpoletis chlorideae和斑痣悬茧蜂Meteorus pulchricornis,并对主要寄生蜂与斜纹夜蛾幼虫的田间消长动态进行了系统观察。     

Larval cannibalism during the late developmental stages of a facultatively gregarious encyrtid endoparasitoid

• 1 The larvae of many gregarious parasitoid species are usually non‐aggressive when they develop in or on a host, but those of Metaphycus flavus are one of the few exceptions known. Herein we describe their aggressive behaviour and the conditions under which it occurs, using observations in which larval development and physical conflict within parasitised and superparasitised hosts were mapped daily.
• 2 Metaphycus flavus larvae often engaged in physical conflict that resulted in consumption of the losing larvae (= cannibalism ) in superparasitised hosts, whereas such conflict and consumption occurred rarely when a single brood developed in a host.
• 3 Cannibalism among M. flavus larvae only occurred after the host resources had become scarce. Typically it occurred after the sixth day of development (fourth‐instar larvae) when the larvae in a clutch had separated from their aeroscopic plate and were freed of their attachment to the host's cuticle.
• 4 Female larvae in the initial clutch appeared more aggressive than male larvae when a second clutch was allocated 4 h after the first clutch. The probability of a larva being attacked and consumed by a brood mate increased as the number of larvae increased in the host. This partial tolerance might allow the members of the initial brood to defend themselves from offspring of a superparasitising female (= competitors ). Such post‐ovipositional regulation of brood size might be interpreted as high‐density intolerance among female offspring.

     

The Race for Females: The Mating System of the Red Mason Bee, Osmia rufa (L.) (Hymenoptera: Megachilidae)

The ecology of a species strongly influences the strategies with which males and females maximize their lifetime reproductive success. When males and females do not invest equally in offspring, the sex with the higher parental investment becomes a rare resource for the other. The spatial and temporal distribution of the limiting sex forms the basis of the mating system. In nest-constructing Aculeata such as the red mason bee, Osmia rufa, females perform intensive brood care, whereas males do not invest in their offspring but instead compete for access to mates. Receptive females of this species are widely distributed and do not assemble at certain places. Therefore, territorial behavior is not an advantageous mating tactic for males, which instead search for females within individual home ranges usually centered around food plants. The unmarked or defended home ranges of different males may completely overlap. Competitive searching leads to a random distribution of matings among males that is largely independent of body size. The mating system of O. rufa can be described as scramble competition polygyny.     

Sex ratio regulation in the waspEupelmus vuilleti (crwf.), an ectoparasitoid on bean weevil larvae (Hymenoptera: Pteromalidae)

In Africa, the seeds and/or pods ofVigna unguiculata andVigna radiata (Papilionacea) are attacked in fields and storage structures by bruchid beetlesCallosobruchus maculatus andBruchidius atrolineatus, on which parasitoid communities can develop. One of these parasitoids is the solitary ectoparasitoidEupelmus vuilleti (Eupelmidae). The storage conditions ofV. unguiculata andV. radiata favor the overlapping of all host stages during several months. These conditions suggest that female parasitoids would vary the sex ratio of their offspring according to the different sizes or developmental stages of hosts. The sex ratio ofE. vuilleti was strongly related to the developmental stage of the hostC. maculatus. Under our experimental conditions, where superparasitism is rare, the proportion of daughters varied between 5 and 25% on the third larval stage but reached 70 to 90% on the pupae. The increase in the proportion of daughters was also observed in the absence of superparasitism. In this case, there was an absolute coincidence between the sex ratio of eggs laid and that of emerged adults. Manipulation of the sex of the egg by the females seems to take place at the time of the egg's fertilization. The relation between host weight and egg sex showed that the male eggs are preferentially laid on lighter host larvae and the female eggs on heavier ones.     

Thermal change alters the outcome of behavioural interactions between antagonistic partners

1. Concerns about climate change often trigger the question whether physiological and behavioural responses of species will enable them to persist. However, species do not exist alone and are largely dependent on interactions with others within communities. 2. In the present study, a mechanistic approach is used to test the hypothesis that inter‐specific differences in metabolic response to unpredictable short‐term thermal changes can change the outcome of host–parasitoid behavioural interactions. 3. The effect of a drop or a rise of 5 °C on resting metabolic rates (RMR) of the main aphid pest of cereal crops in Western Europe, the host Sitobion avenae Fabricius and its main natural enemy, the parasitoid Aphidius rhopalosiphi De Stefani‐Perez was measured. Also, defence and attack behaviours were measured for host and parasitoid separately as well as in interaction, since behavioural strategies of both species largely determine parasitism success. 4. The results showed that, when no change in temperature occurred, parasitoids had the highest oviposition rate. However, only with a rise of temperature behavioural interactions were disrupted: the parasitoid attack rate decreased whereas the aphid defence rate increased. This alteration in behaviour was associated with a stronger thermal response of RMR in hosts than in parasitoids, suggesting that species‐specific thermal responses of RMR could give valuable information on changes in the outcome of species interactions under warm spells but not under cold ones. 5. It was shown that relatively modest thermal changes with non‐lethal effects can have profound consequences for interacting co‐evolved species which may affect ecosystem services, such as biological control of pest populations.