EJE, vol. 90 (1993), issue 4

Behavioural Ecology of Aphidophagous Insects. Proceedings of the Fifth Symposium of the Global I.O.B.C. Working Group Ecology of Aphidophaga.


Eur. J. Entomol. 90 (4): 1993


Towards a general theory of host acceptance by aphid parasitoids


Eur. J. Entomol. 90 (4): 369-376, 1993

I present the thesis that the most effective means of developing a unified theory of host exploitation by aphidophagous insects would be through a rational, first-principles approach. This approach entails the use of life history theory wherein host acceptance ''decisions'' are evaluated on the basis of contribution to current and future lifetime reproductive success wherein future success is discounted by life expectancy. A simple example involving egg load and host discrimination demonstrates the value of dynamic life history theory as a means of structuring experimental and empirically based research programs. Finally, I argue that a unified theory...

Foraging behaviour in aphid parasitoids: Spatial scale and resource assessment


Eur. J. Entomol. 90 (4): 377-382, 1993

This review examines recent research on the foraging behaviour of aphid parasitoids and highlights current knowledge on host location, searching mechanisms and variation in parasitoid performance. In addition, the theoretical relationships between host spatial distribution and parasitoid behaviour are explored. Predictions from this theoretical framework are compared with results from recent experimental studies on foraging behaviour.

Foraging behaviour of ladybird larvae (Coleoptera: Coccinellidae)


Eur. J. Entomol. 90 (4): 383-402, 1993

Coccinellids, particularly their larvae are very voracious. Their foraging behaviour has been extensively studied in an attempt to determine their potential for controlling pest aphids, which occur in patches that are relatively short lived and within which the aphids are not uniformly distributed but clumped. In seeking aphid prey ladybirds like other insect predators forage both extensively and intensively, and use visual and olfactory cues for orientation. Intensive search follows an encounter with an aphid and serves to keep the predator in the vicinity of a cluster of prey. The success of larvae in capturing prey is dependent on abiotic and biotic...

Long-distance flights in Coccinellidae (Coleoptera)


Eur. J. Entomol. 90 (4): 403-414, 1993

In the period of reproductive activity and foraging for prey coccinellids undertake trivial (appetitive) flights. The irregular long-distance flights of ''swarms'' of ladybirds originate in hypermobility of starving beetles of the new generation. Two types of regular long-distance flights are related to dormancy: diapausing coccinellids migrate to dormancy sites by directional flight and after dormancy they disperse gradually to breeding sites. There is abundant evidence that most long-distance migrants are hypsotactically attracted to prominent landmarks, at least in the closing part of their migratory flight. None of the methods used to quantify...

Flight behaviour of the aphid parasitoid Aphidius ervi (Hymenoptera: Braconidae) in response to plant and host volatiles


Eur. J. Entomol. 90 (4): 415-421, 1993

The flight behaviour of the aphid parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) has been studied in a wind tunnel, in response to the following natural odour sources: broad bean plants infested with Acyrthosiphon pisum (Harris) (Homoptera: Aphididae) (PHC, plant-host complex), damaged broad bean plants from which the aphids were removed (HDP, host damaged plants), aphids (H, host) and uninfested broad bean plants (P, plant). The most attractive odour sources were PHC and HDP, which both stimulated a similar high number of oriented straight flights. In contrast, H and P were much less attractive and did not seem to be important...

Cornicle secretion of Acyrthosiphon pisum (Homoptera: Aphididae) as a contact kairomone for the parasitoid Aphidius ervi (Hymenoptera: Braconidae)


Eur. J. Entomol. 90 (4): 423-428, 1993

Females of the endophagous parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) respond positively to the cornicle secretion of the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae). The parasitoid response has been assessed in a Petri dish choice test by presenting an aphid dummy consisting of a glass bead coated with cornicle secretion along with an untreated bead, which acted as a control. Naive females responded similarly to the treated glass beads and aphids, while experienced females responded less to the treated beads than to aphids. The kairomonal activity of the cornicle secretion decreased as the wax dried....

A general approach to oviposition strategies in solitary parasitoids


Eur. J. Entomol. 90 (4): 429-434, 1993

Foraging theory has largely concentrated on oviposition rate as the currency parasitoids use to maximize reproductive success. Female parasitoids foraging in a patchy environment face a variety of mortality risks that influence the survival of both themselves and their offspring. A foraging model is developed to suggest that patch residence times in parasitoids should be based on the trade-off between female and offspring mortality risks.

The fitness gain of parasitoids that include all mortality risks in their calculation of optimal patch residence time is then compared to the fitness gain of rate-maximizing females, and to the fitness gain...

Responses of the parasitoid Praon volucre (Hymenoptera: Braconidae) to aphid sex pheromone lures in cereal fields in autumn: Implications for parasitoid manipulation


Eur. J. Entomol. 90 (4): 435-438, 1993

Females of the aphid parasitoid Praon volucre were attracted to lures containing synthetic aphid sex pheromone components, particularly (+)-(4aS,7S,7aR)-nepetalactone, when these were placed on water traps in cereal fields in autumn. Trap catches were greatest at a site in S.W.England and fewest at sites in northern England 'and northern Germany, presumably due to climatic differences. Responses to the pheromones were not detected for any other cereal aphid parasitoids in the field trials, although Aphidius rhopalosiphi appears to possess olfactory receptors for (+)-(4aS,7S,7aR)-nepetalactone. A potential strategy for the use of aphid...

6-methyl-5-heptene-2-one, a putative sex and spacing pheromone of the aphid hyperparasitoid, Alloxysta victrix (Hymenoptera: Alloxystidae)


Eur. J. Entomol. 90 (4): 439-442, 1993

Hyperparasitoids are, considered to reduce the effectiveness of primary parasitoids as biological control agents of aphids in a variety of crops. Recently it was shown that volatiles produced by the hyperparasitoid Alloxysta victrix (Westwood) elicit a dispersal in female primary parasitoids thereby potentially reducing primary parasitoid activity in the field at certain times. The active chemical was identified as 6-methyl-5-heptene-2-one (MHO) which is produced by both male and female A. victrix. The function of this chemical in the intraspecific communication of A. victrix was studied. Y-tube olfactometer experiments revealed...

Optimal foraging in ladybird beetles (Coleoptera: Coccinellidae) and its consequences for their use in biological control


Eur. J. Entomol. 90 (4): 443-450, 1993

A model optimizing the number of eggs laid in an aphid colony by an adult ladybird reveals that there exists an optimum number, which maximizes the resulting offspring biomass. This remains true even if the model is expanded to include more than one adult ladybird and several aphid colonies. Adult ladybirds should not continue to aggregate in areas of aphid abundance (Kareiva & Odell, 1987), but should leave an aphid aggregate, even though the aphids are still increasing in abundance, as soon as a certain number of eggs are laid and/or larvae are present. If the ladybirds lay the optimal number of eggs, then their offspring have only a slight effect...

Optimal foraging by hoverflies (Diptera: Syrphidae) and ladybirds (Coleoptera: Coccinellidae): Mechanism


Eur. J. Entomol. 90 (4): 451-455, 1993

Coccinellids and syrphids that feed on aphids and coccids face the same problem: an unstable food supply. Their eggs and larvae face cannibalism and/or starvation if the aphid colony they attack declines in abundance before they mature. Optimal foraging theory predicts that such predators should lay a few eggs early in the development of an aphid colony. Studies on two species of coccinellid and one species of syrphid revealed that they do respond to the quality as well as the abundance of their prey. By refraining from laying eggs in aphid colonies already exploited by predators and those that are shortly to decline in abundance when the aphids disperse,...

Egg and cluster size in ladybird beetles (Coleoptera: Coccinellidae): The direct and indirect effects of aphid abundance


Eur. J. Entomol. 90 (4): 457-463, 1993

Food stress experienced during larval and adult life in Coccinella septempunctata L. results in variation in the rate of production of eggs per unit time and in the size of egg clusters but not in egg size. This lends support to the suggestion that egg size is constrained by the minimum size at which first instar larvae can capture active prey and/or complete their development before prey become scarce. When supplied with an excess of food large beetles produce larger clusters of eggs than small beetles. This is associated with the large females having more ovarioles in their gonads than small females. As the proportion of eggs that give rise...

Comparison of cold hardiness in two ladybird beetles (Coleoptera: Coccinellidae) with contrasting hibernation behaviour


Eur. J. Entomol. 90 (4): 465-470, 1993

The cold hardiness of two ladybird species from the Czech Republic, Coccinella septempunctata and Semiadalia undecimnotata, was measured in terms of their supercooling point (SCP) and survival at subzero temperatures. The SCP was lower in diapausing beetles in late summer than in active beetles, and the SCP of diapausing beetles decreased slowly until mid-winter. The SCP of S. undecimnotata, which overwinters exposed to air, was lower (to -19C), that of C. septempunctata, which overwinters at ground level insulated in plant material, was higher (to -15C). The SCP of C. septempunctata, exposed to extreme fluctuations...

Functional response, multiple feeding and wasteful killing in a wolf spider (Araneae: Lycosidae)


Eur. J. Entomol. 90 (4): 471-476, 1993

Feeding behaviour of the wolf spider Pardosa hortensis Thorell (Araneae: Lycosidae) was studied in the laboratory under different prey densities. Feeding characteristics were monitored by a behaviour registering computer program. The amount of prey eaten in the different prey density treatments indicated a Holling type II functional response. Handling time was negatively correlated with prey density. At higher prey densities spiders sometimes attacked and fed on more than one prey item at the same time. Consumption rate during such multiple feeding events was higher than during single feeding. However, multiple feeding was much less frequent...