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Summary We investigated how the plant-inhabiting, anthocorid predator, Anthocoris nemoralis, copes with variation in prey, host plant and associated herbivore-induced plant volatiles and in particular whether the preference for these plant odours is innate or acquired. We found a marked difference between the olfactory response of orchard-caught predators and that of their first generation reared on flour moth eggs in the laboratory, i.e. under conditions free of herbivory-induced volatiles. Whereas the orchard-caught predators preferred odour from psyllid-infested pear leaves, when offered against clean air in a Y-tube olfactometer, the laboratory-reared first generation of (naive) predators did not. The same difference was found when a single component (methyl salicylate) of the herbivore-induced plant volatiles was offered against clean air. After experiencing methyl salicylate with prey, however, the laboratory-reared predators showed a pronounced preference for this volatile. This acquired preference did not depend on whether the volatile had been experienced in the juvenile period or in the adult phase, but it did depend on whether it had been offered in presence or absence of prey. In the first case, they were attracted to the plant volatile in subsequent olfactometer experiments, but when the volatile had been offered during a period of prey deprivation, the predators were not attracted. We conclude that associative learning is the most likely mechanism underlying acquired odour preference.

When the chemical cues co-occurring with prey vary in time and space, foraging predators profit from an ability to repeatedly associate chemical cues with the presence of their prey. We demonstrate the ability of a predatory arthropod (the plant-inhabiting mite, Phytoseiulus persimilis) to learn the association of a positive stimulus (herbivorous prey, Tetranychus urticae) or a negative stimulus (hunger) with a chemical cue (herbivore-induced plant volatiles or green leaf volatiles). It has been suggested that the rate at which the integration of information becomes manifest as a change in behaviour, differs between categories of natural enemies (parasitoids versus insect predators: specialist versus generalist predators). We argue that these differences do not necessarily reflect differential learning ability, but rather relate to the ecologically relevant time scale at which the biotic environment changes.

Summary 1. To test whether predatory anthocorids migrate into pear orchards when populations of pear psyllids are building up, a cross-correlation analysis was carried out on their population numbers. Predator and prey population sizes were assessed weekly in 3 consecutive years (1991–93) by sampling pear leaves for eggs and nymphs of psyllids and pear tree branches for adult psyllids, as well as adults and nymphs of predatory anthocorids. The time-series consisted of numbers (per leaf or branch) averaged over preselected pear trees in an orchard and, in addition, over other trees selected along the hedgerows flanking the orchard. 2. The fluctuations in populations of adult and juvenile anthocorids showed strong cross-correlations with those of the eggs and nymphs of pear psyllids, but less correlation with adults of pear psyllids, as expected based on their increased ability to escape from predation. The psyllids always appeared first on the pear trees, resulting in positive phase shifts. The first peak of adult anthocorids on pear trees was always later than the first peak in the hedgerows, and the first peak of nymphal anthocorids on pear trees was always later than the first peak of adults on these pear trees. In each of the 3 years, anthocorids were rarely observed in the pear orchard during the first part of the growing season (April–June), but during the second half of the growing season (July–August) there was a strong numerical response of the anthocorid populations to increasing population densities of pear psyllids. 3. These results provide support for the hypothesis that the numerical response of the predators to prey density is caused initially by migration of anthocorids into the pear orchard and then by a reproductive response. The migrants originate from the hedgerows and other trees elsewhere, where they feed on aphids during the first part of the growing season.

Because Y-tube olfactometer experiments in the laboratory showed a response of anthocorid bugs to odour from Psylla-infested leaves, it was of interest to assess its relevance under field circumstances. This was done by measuring the density of predatory bugs on pear trees adjacent to Psylla-infested or control trees that were covered with fine mesh gauze-screens. In this way odours from these caged trees could spread through the screen, while contact with the Psylla prey in the cage was prevented. The density of anthocorid predators around cages with heavily infested trees was significantly higher than around uncaged control trees and around cages containing uninfested or little infested trees. Covering a cage with Psylla-infested trees by an airtight plastic sheet led to an immediate drop in the density of anthocorid predators, whereas removal of the sheet led to predator aggregation again. The results of these field experiments strongly support the hypothesis that anthocorid predators respond to volatile chemicals emanating from Psylla-infested pear trees.

Behavioural and endocrine parameters were studied in a large colony of stumptail macaques. This paper deals with harassment behaviour during copulation, and its possible underlying motivation. The study corroborates some findings of other studies such as that harassment is triggered by ejaculation and is directed at the mating male. Both males and females harassed most frequently around puberty, but only females continued to harass when adult, although at a lower rate, especially when pregnant. Harassment was seldom retaliated, even when severe aggression to dominant mating males was involved. Social factors that correlated with harassment included family ties, affiliative ties and reciprocity between harasser and female copulant, dominance status and aggression between harasser and male copulant. Motivational factors appeared not to be exclusively associated with the harassers' attitude towards the female copulant, as other studies suggested, but also involved the harassers' attitude towards the male copulant since the behaviour was invariably directed at him. In addition to possessiveness, it is suggested that revanchism may be a motive. Because of aggression received earlier, monkeys take ‘revenge’ when they have an opportunity, i.e. when the opponent is mating and at the moment of orgasm. It is suggested that, as an evolutionary mechanism, harassment reinforces power structures in the group. Harassers may unwittingly serve as sentinels for top-ranking males who thus become better able to monopolize fathership. As an additional effect, high-ranking matrilines can grow at the cost of low-ranking ones because of the preference of top-ranking males for high-ranking females.

Qualitative and quantitative differences among pear cultivars were found in constitutive and Cacopsylla-induced volatiles, depending on experimental treatment of the trees (i.e., uninfested and partly or completely infested by psyllids). Blend differences were also found between pear cultivars and wild-type pear, alder and hawthorn-the latter trees are frequently present in pear orchard hedgerows. Interesting differences were found in the presence of methyl salicylate and (E,E)-alpha-farnesene, two compounds previously found to mediate attraction of predatory bugs towards psyllid-infested pear trees. Methyl salicylate is expressed constitutively and is induced systemically by infestation in the whole plant of all four cultivars. (E,E)-alpha-farnesene on the other hand showed also systemic induction in Bartlett, NY10355 and Beurre Hardy, but in partially infested Conference trees it was induced locally, only in herbivore-damaged leaves. No methyl salicylate or (E,E)-alpha-farnesene were identified in honeydew. In field collected headspace samples of alder leaves infested by aphids and leaf beetles we found methyl salicylate but no (E,E)-alpha-farnesene, whereas in uninfested hawthorn neither were identified. Insight in the variability of damage-related pear volatiles will have important implications for integrated pest management in the field.

When the chemical cues co-occurring with prey vary in time and space, foraging predators profit from an ability to repeatedly associate chemical cues with the presence of their prey. We demonstrate the ability of a predatory arthropod (the plant-inhabiting mite, Phytoseiulus persimilis) to learn the association of a positive stimulus (herbivorous prey, Tetranychus urticae) or a negative stimulus (hunger) with a chemical cue (herbivore-induced plant volatiles or green leaf volatiles). It has been suggested that the rate at which the integration of information becomes manifest as a change in behaviour, differs between categories of natural enemies (parasitoids versus insect predators: specialist versus generalist predators). We argue that these differences do not necessarily reflect differential learning ability, but rather relate to the ecologically relevant time scale at which the biotic environment changes.

Plants provide protection (domatia), alternative food (nectar, exudates, pollen) and chemical lures which benefit predatory arthropods and thereby protect plants against herbivorous arthropods. Experimental evidence for these indirect effects is reviewed and hypotheses are provided to explain why plants invest in attracting, feeding and protecting predatory arthropods despite the fact that (1) other organisms not beneficial to the plant may utilize these facilities too, and (2) also competing neighbour-plants may profit from these investments. It is argued that although the plant may benefit under certain conditions, plant-bodyguard interactions do not have a single anticipated outcome. Instead, these interactions may have a range of positive, neutral and negative outcomes, the exact value of which depends on position in space and moment in time. The benefits to the plant investing in indirect defence depend on the availability and responsiveness of predatory arthropods, the abundance and responses of cheaters, the degree to which neighbouring plants profit from these investments, and the extent to which other plants in the environment invest or harbour profitable prey. Possibilities for indirect plant defence to arise from coevolution are discussed.

Previous work showed that anthocorid predators aggregate around gauze cages containing Psylla-infested trees in a pear orchard. Because anthocorids responded to odor from Psylla-infested leaves in a laboratory test, it was hypothesized that these aggregative responses in the field were triggered by olfaction of compounds associated with Psylla injury. We present chemical analyses of volatiles from damaged and undamaged plants and studies on behavioral responses of anthocorid predators to compounds released by damaged plants. Leaf headspace volatiles from clean and Psylla-infested pear trees were collected on Tenax and identified by GC-MS after thermodesorption. Twelve volatiles were found exclusively in headspace samples from Psylla-infested leaves. Six were present in significantly higher quantities in samples from infested leaves: the monoterpene, (E,E)-?-farnesene, the phenolic, methyl salicylate, and the green leaf compounds, (Z)-3-hexen-1-yl acetate, (Z)-3-hexen-1-ol, 1-hexyl-acetate, and 1-penten-3-ol. These compounds are known to be produced by plants, and damage by pear psyllids seems to trigger their emission. Blend composition varied and was partly correlated with tree or leaf age and degree of Psylla infestation. To study whether compounds associated with leaf injury elicit olfactory responses in anthocorid predators, apple-extracted (E,E)-?-farnesene, synthetic methyl salicylate, and (Z)-3-hexen-1-yl acetate were offered in a Y-tube olfactometer to field-collected adult Anthocoris spp. Significant positive responses were found to both the monoterpene and the phenolic, but not to the green leaf volatile. The results lend support to the hypothesis that predator attraction to herbivore-infested pear trees is mediated by herbivory-induced plant volatiles.

Feeding by the homopteranPsylla pyricola on leaves of pear trees induces the production of volatile compounds, such as (E,E)-α-farnesene and methyl-salicylate, as well as the production of polyphenols. The inference on induction is based on GC-MS and HPLC chromatograms from the same samples ofPsylla infested leaves, leaves from the same pear tree beforePsylla infestation and uninfested leaves from other pear trees.Psylla infestation greatly enhanced the production of volatiles ((E,E)-α-farnesene, methyl-salicylate and others) and triggered the production of new polyphenols, characterized by much longer retention times.

A survey of historical ammonia (NH3) emissions is presented for individual European countries (excl. the U.S.S.R. and Turkey). From 1870 to 1980 the annual total NH3 emission from livestock wastes, fertilizer application and the fertilizer industry has increased from 2.2 to 4.7 Mt of NH3. A Lagrangian long-range transport model is used to calculate the change in concentration and deposition of ammonia (NH3) and ammonium (NH+4) in Europe over the same period. It is shown that the percentage of increase in concentration and deposition during this period varies regionally. The modelled increase of NH+4 concentration in precipitation is shown not always to be in agreement with historical measured concentrations.

A randomized, prospective, double-blind study was designed to compare intravenous administration with intrauterine irrigation using an extended half-life (t1/2 = three hours) cephalosporin, ceforanide. Patients included in the study had a nonelective cesarean section with rupture of membranes for three hours or longer. Sixty-four patients received a single dose of ceforanide immediately after clamping the umbilical cord. Patients were similar in both groups in age, weight, length of labor, and duration of ruptured membranes. The group receiving the intravenous ceforanide had a significantly shorter duration of surgery than the patients receiving the intrauterine ceforanide. Endometritis infection rates were similar, 11.8% (intravenous) versus 11.1% (intrauterine), P greater than .1. Serum levels were as much as tenfold higher in the intravenous group versus the intrauterine group. Intrauterine irrigation with an antimicrobial agent provided no advantage over systemic administration.

The predatory mite Phytoseiulus persimilis is frequently reported to perform poorly on greenhouse tomatoes. As the predators are mass-reared on another host plant (bean), we supposed that they are poorly adapted to tomato, a plant densely packed with poisonous and sticky glandular hairs. This hypothesis was tested by comparing the control capacity of a stain of P. persimilis directly obtained from a mass rearing with the same strain after four generations on tomato. Both strains were released in a tomato crop in two identical compartments of a greenhouse and the population dynamics of prey (a tomato strain of Tetranychus urticae) and predator were recorded at weekly time intervals. It was found that the strain previously exposed to a tomato environment performed better than the unexposed strain: (1) its population increased faster; (2) the prey population declined faster; and (3) the damage to new-grown tomato leaves was considerably lower. To investigate the causes of the difference in performance between the exposed and unexposed strains, oviposition and survival rates were assessed on a diet of two-spotted spider mites on tomato leaf sections. In addition, the unexposed strain was tested on a diet of two-spotted spider mites on bean leaf sections. The difference in oviposition rates of both predator strains was small compare to the overall mean. However, the oviposition rate of the first generation of predators since transfer from bean to tomato dropped to less than half of the original value. Moreover, mortality in the first generation increased from 14% to 89%, whereas it decreased to 0% after four generations. Future research should clarify whether these changes in life history are due to selection or to physiological adaptation.