In vitro rearing ofExorista larvarum on tissue culture-based diets

Exorista (=Tachina) larvarum (L.) (Diptera, Tachinidae), a polyphagous parasitoid that attacksLymantria dispar L. andHyphantria cunea (Drury), was rearedin vitro from egg to adult on four tissue culture media-based diets (TMM-FH, SCHNEIDER'S, EX-CELL 400, and SF-900). The kind of tissue culture media in the diets did not influence the adult yield (34 to 55%) and puparium weight (26–27 mg). Adult yield and the puparium weight ofE. larvarum developed on TNM-FH and SCHNEIDER'S-based diets containing different amounts ofGalleria mellonella pupal extract (PE) (0, 1.25, 2.5 and 5%), were lower on diets without PE. In diets without PE development times from oviposition to adult emergence, were shorter on TNM-FH (19 days) than on SCHNEIDER'S-based diet (25–26 days). The adults that developed on artificial diets were able to parasitize the factitious hostG. mellonella and produce viable progeny. The results demonstrate thatE. larvarum is the most promising parasitoid ever studied forin vitro mass production.     

伊朗八种跳小蜂及一新种记述（膜翅目：小蜂总科）

报道由伊朗设拉子大学农学院采集饲出的与林木害虫有关的７属８种寄生蜂,它们均属膜翅目小蜂总科、跳小蜂科,扬与林木介壳虫有关的Ａｎａｇｙｒｕｓ ｐｓｅｕｄｏｃｏｃｃｉ,Ｃｈｅｉｌｏｎｅｒｒｕｓ ｃｅｒｏｐｌａｓｉｔｓ,Ｄｕｓｍｅｔｉａ ｆａｓｃｉｐｅｎｎｉｓ,Ｈｏｍａｌｏｔｙｌｕｓ ｅｐｈｉｐｐｉｕｍ,与草蛉有关的Ｉｓｏｄｒｏｍｕｓ ａｔｒｉｖｅｎｔｒｉｓ,Ｉｓｏｄｒｍｕｓ ｃｏｌｌｉｍａｃｕｌａｔｕ     

The oviposition behavior ofAphidius ervi andMonoctonus paulensis (Hymenoptera: Aphididae) encountering different host species (Homoptera: Aphididae) in sequential patches

Two-day-old mated females ofAphidius ervi Haliday andMonoctonus paulensis (Ashmead) were each provided with two sequential host patches. Patches were comprised of plastic petri dishes containing either 15 pea aphids,Acyrthosiphum pisum (Harris), or 15 alfalfa aphids,Macrosiphum creelii Davis. Both wasp species parasitized more hosts in patches containing pea aphids than in those containing alfalfa aphids, regardless of sequence. Females ofA. ervi also laid more eggs per aphid in patches containing pea aphids than in patches containing alfalfa aphids. When both patches contained alfalfa aphids,M. paulensis females parsitized more aphids in the second patch than in the first. Fewer alfalfa aphids were parasitized in the second patch when the first patch contained pea aphids, and fewer eggs were laid per alfalfa aphid. Parasitoid females of both species exhibited consistently higher rates of oviposition into their preferred host species and adjusted their reproductive allocation to hosts and host patches as a function of their experience in previous patches.     

Development of an Oligidic Diet forin VitroRearing ofTrichogramma galloiZucchi andTrichogramma pretiosumRiley

The goal of this research was to develop an artificial diet for rearingTrichogramma galloiandTrichogramma pretiosum,which are important egg parasitoids of several pests in Brazil. The diet was based on different proportions of hemolymph ofHelicoverpa zealarvae, chicken egg yolk, powdered milk solutions, bovine fetal serum, and an extract fromHeliothis virescenseggs. The ideal volume of diet for rearingT. galloiwas also evaluated. The parasitoids showed different nutritional requirements for their development. The best proportion of diet components forT. galloiwas 70% hemolymph, 20% egg yolk, 10% fetal serum, and 0.2% streptomycin, and forT. pretiosumit was 70% hemolymph, 20% egg yolk, 5% fetal serum, 5% egg extract, and 0.2% streptomycin. Egg yolk was found to be essential for the development of both parasitoids, and the powdered milk solution was not an important component in the diet. Development was not obtained in diets with hemolymph concentrations lower than 40%. A 3- to 4-μl amount of diet was the ideal volume on which to rearT. galloiwith the techniques reported.     

To mark the host or the patch: Decisions of a parasitoid searching for concealed host larvae

We found evidence for patch marking in the parasitic wasp Halticoptera laevigata (Hymenoptera: Pteromalidae) foraging for concealed hosts. Wasps attack larvae of the fruit fly Myoleja lucida (Diptera: Tephritidae) in fruits of honeysuckle. A special feature of this host-parasitoid system is the limited food supply of a patch (i.e. a fruit of honeysuckle), which allows the successful development of only a single host fly larva. Females of the parasitoid H. laevigata were found to mark the host patch with a pheromone and to abandon the patch following oviposition into a single host larva. Field data revealed that eggs of the parasitoid were spread out evenly among infested patches, with several larvae of the host fly left unparasitized in those patches that contained more than one host. Since many parasitic insects mark the parasitized host after oviposition, we assumed host marking to be the ancestral character state and studied the patch-marking behaviour of H. laevigata as a derived character state as an alternative foraging strategy. We used stochastic dynamic modelling to investigate under what conditions mutant (patch) markers would be able to invade a population of normal (larval) markers. The models suggested that, under a variety of conditions, wasps marking the patch obtained higher fitness than wasps only marking the larva. Consequently, the results from our model predict the evolution of the patch-marking behaviour found in the empirical investigation. Finally, we discuss alternative pathways to the evolution of patch marking and point out under what circumstances the evolution of a patch-marking behaviour can generally be expected.     

Genetic covariation between effectiveness and cost of defence in aphids

Ecological immunology distinguishes between the long-term evolutionary costs of possessing defences against parasites and the short-term costs of using them. Evolutionary biologists have typically focused on the former in the search for constraints on the evolution of resistance. Here, we show in the peach-potato aphid, Myzus persicae, that short-term costs may be of equal evolutionary importance. Survivors of more resistant aphid clones suffered a higher reduction of fecundity upon parasitoid attack than survivors of more susceptible clones. This genetically based trade-off between benefits and costs of defence may limit the evolution of increased resistance and explain the maintenance of genetic variation for resistance under environmental variation in parasitism risk.     

In situ modification of herbivore-induced plant odors: a novel approach to study the attractiveness of volatile organic compounds to parasitic wasps

Many parasitic wasps (parasitoids) exploit volatile organic compounds (VOCs) emitted by herbivore-infested plants in order to locate their hosts, but it remains largely unknown which specific compounds within the volatile blends elicit the attractiveness to parasitoids. One way of studying the importance of specific VOCs is to test the attractiveness of odor blends from which certain compounds have been emitted. We used this approach by testing the attraction of naive and experienced females of the two parasitoids Cotesia marginiventris and Microplitis rufiventris to partially altered volatile blends of maize seedlings (Zea mays var. Delprim) infested with Spodoptera littoralis larvae. Adsorbing filter tubes containing carbotrap-C or silica were installed in a four-arm olfactometer between the odor source vessels and the arms of the olfactometer. The blends breaking through were tested for chemical composition and attractiveness to the wasps. Carbotrap-C adsorbed most of the sesquiterpenes, but the breakthrough blend remained attractive to naive C. marginiventris females. Silica adsorbed only some of the more polar VOCs, but this essentially eliminated all attractiveness to naive C. marginiventris, implying that among the adsorbed compounds there are some that play key roles in the attraction. Unlike C. marginiventris, M. rufiventris was still attracted to the latter blend, showing that parasitoids with a comparable biology may employ different strategies in their use of plant-provided cues to locate hosts. Results from similar experiments with modified odor blends of caterpillar-infested cowpea (Vigna unguiculata) indicate that key VOCs in different plant species vary greatly in quality and/or quantity. Finally, experienced wasps were more strongly attracted to a specific blend after they perceived the blend while ovipositing in a host. Considering the high number of distinct adsorbing materials available today, this in situ modification of complex volatile blends provides a new and promising approach pinpointing on key attractants within these blends. Advantages and disadvantages compared to other approaches are discussed.     

Entomophagous insects – an introduction

This special issue contains papers presented at the 6th International Entomophagous Insects Conference. Entomophagous insects consume other insects. They are a fundamental component of ecosystems and are extensively used as biocontrol agents. The first article reviews the role of ladybirds in biological control and the second reviews the biological control of stink bugs. The following nine research articles cover the rearing, behavior, life history, and ecology of parasitoid and predator species.     

Is there any evidence that aphid alarm pheromones work as prey and host finding kairomones for natural enemies?

1. The aphid alarm pheromone (E)‐β‐farnesene (EBF) is often considered to be used by natural enemies as a prey/host finding kairomone. However, studies show opposing results, some appear to confirm an attraction of aphid natural enemies by EBF whereas others do not provide any evidence for the kairomone function of EBF. 2. To clarify if aphid natural enemies are attracted by the amounts of EBF naturally emitted by aphids, the existing literature was reviewed about EBF attractiveness to aphid natural enemies with consideration of the amounts of EBF used in the studies. 3. Thirty‐one publications that investigated the ability of EBF, aphid cornicle secretion, and attacked aphids, to attract aphid natural enemies were found. Several studies showed an attraction by EBF, but these used much higher amounts of EBF than usually emitted by aphids during a predator attack. Studies investigating EBF amounts similar to what is emitted by aphids are rare and failed to show attraction. Only two studies document an attraction of natural enemies by attacked aphids. 4. As EBF is emitted in very low amounts, not very stable, and only present after an attack, we suggest that aphid‐derived EBF is not a suitable kairomone for most natural enemy species, especially when they are able to use alternative cues. As EBF, amongst other volatiles, is also emitted by herbivore‐induced plants, we propose that natural enemies might use plant‐derived EBF as a synomone to identify aphid‐infested plants via an altered plant volatile bouquet.     

Can plant–natural enemy communication withstand disruption by biotic and abiotic factors?

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