Detection of refuge from enemies through phenological mismatching in multitrophic interactions requires season-wide estimation of host abundance

The concept of ‘‘enemy-free space’’ (EFS) refers to ways of living that reduce or eliminate the vulnerability of a species to natural enemies. It has been invoked to explain host shifts of phytophagous insects. A demonstrated cause of EFS is escape from enemies in time, through phenological mismatching of herbivore development and enemy occurrence, leading to low percentages of predation/parasitism of herbivores occurring at a certain time. The mere measurement of percentage parasitism, however, is not sufficient to demonstrate EFS in certain cases. Here we present such a case, where parasitism was studied of a phytophagous insect (Phyllotreta nemorum), using two different host plant species in the field: an atypical, relatively rarely used, plant (Barbarea vulgaris), and a more widely used one (Sinapis arvensis). At one location we found a paradoxical result: on each separate sampling day throughout the season the percentage of parasitism of P. nemorum using a patch of B. vulgaris was not significantly different from, or even significantly higher than on a nearby patch of S. arvensis. The overall season-wide proportion parasitism of the flea beetle cohort using the B. vulgaris patch, however, was lower. We conclude that, in the year and at the location we studied, the patch of B. vulgaris provided enemy-free space to the herbivore in the form of a temporal refuge, and that the importance of enemy-free space in the use of an atypical host plant should be evaluated on the basis of season-wide sampling, including estimation of host population size

De wapenwedloop tussen plant en insect

Meer dan de helft van alle bekende insecten leeft van planten. Niet alleen insecten passen zich aan hun voedsel aan. Ook de plant wapent zich tegen zijn belagers. Hoe is deze situatie ontstaan? Hoe verdedigen planten zich tegen insectenvraat, en hoe 'ontmantelen' sommige insecten deze verdediging

Insecten in het veranderende klimaat

Het succes van insecten is rechtstreeks afhankelijk van het klimaat. Daarom mag je verwachten dat klimaatsverandering een heel directe invloed heeft op insecten en andere koudbloedigen. Als je weet hoe belangrijk insecten zijn in ecosystemen dan kun je wel nagaan wat de impact zal zijn van klimaatsverandering op het leven op aard

What does the CBM-maze test measure?

Contains fulltext : 168483.pdf (publisher's version ) (Open Access)In this study, we identified the code-related (decoding, fluency) and language comprehension (vocabulary, listening comprehension) demands of the CBM-Maze test, a formative assessment, and compared them to those of the Gates-MacGinitie test, a standardized summative assessment. The demands of these reading comprehension tests and their developmental patterns were examined with multigroup structural regression models in a sample of 274 children in Grades 4, 7, and 9. The results showed that the CBM-Maze test relied more on code-related than on language comprehension skills when compared to the Gates-MacGinitie test. These demands were relatively stable across grades.13 p

Selection of Bemisia nymphal stages for oviposition or feeding, and host-handling times of arrhenotokous and thelytokous Eretmocerus mundus and arrhenotokous E. eremicus

Host-handling behavior is an important aspect of parasitoid foraging behavior. When a parasitoid encounters a potential host, the handling behavior starts with the evaluation of the host and continues if the host has been judged acceptable. Host handling is usually terminated after egg laying or host feeding and host marking. Host-handling behavior of an arrhenotokous population of two Eretmocerus species, E. mundus Mercet and E. eremicus Rose and Zolnerowich, along with a thelytokous population of E. mundus were compared under laboratory conditions. Several elements of host-handling behavior, including encountering, ascending, turning on host, descending, preening, egg laying, and host feeding were recorded. There were no correlations among the durations of these phases across parasitoid populations/species or host nymphal instars. Duration of different phases of host-handling behavior showed only slight and sometimes significant differences between different Eretmoceruspopulations/species. The actual laying of the egg had the longest duration of all host-handling behaviors, and was longer on third nymphal instars than on younger ones. Females of the three populations/species accepted the first three nymphal stages either for egg laying or for host feeding. Females spent a lot of time to make wounds in the host when preparing for host feeding, and eventually killed the host. The implications of these findings for the use of the different Eretmoceruspopulations/species in biological control are discusse

Chemical defence in ladybird beetles (Coccinellidae). I. Distribution of coccinelline and individual variation in defence in 7-spot ladybirds (Coccinella septempunctata)

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe