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Research article - Peer-reviewed, 2012

Very long diapause and extreme resistance to population disturbance in a galling insect

Solbreck, Christer; Widenfalk, Olof


1. Some insects have a prolonged diapause – a dormancy that extends over more than 1 year. In most species prolonged diapause involves one or a few extra years, but in extreme cases diapause may surpass 10 years. Few cases of very long diapause have been described, and very little is known about the population consequences of the temporal refuge formed by the diapausing individuals. 

2. The gall midgeContarinia vincetoxiciKieffer galls the flowers of a long-lived herbVincetoxicum hirundinariaMed. After completing development, larvae leave the galls for the ground where they enter diapause. Extending an earlier published inoculation experiment, we show that the diapause may last up to at least 13 years, with a median duration of at least 6 years. 
3. The gall midge is attacked by two parasitoid species. Dissections of gall midge larvae for presence of parasitoids revealed thatOmphale salicisHaliday had a maximum 2 year diapause andSynopeas acuminatusKieffer a maximum 4 years. The very long diapause of the gall midge may thus provide a temporal refuge from these enemies. 
4. In a 15-year field experiment all galls were removed every year from six isolated habitat patches. Density changes in experimental populations were not statistically different from control populations for over a decade. After 14–15 years a modest decline could be observed. This slow response illustrates that prolonged diapause inC. vincetoxiciprovides a very strong population buffer against mortality during the galling stage.


Gall midge; perturbation; population density; population resistance; prolonged diapause; swallow-wort

Published in

Ecological Entomology
2012, Volume: 37, number: 1, pages: 51-55

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