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A complex relationship between insects and plants

Carlos Eduardo Nunes / Unicamp Female beetle of the Montella genus deposits an egg in a Dichaea cogniauxiana flowerCarlos Eduardo Nunes / Unicamp

The word pollination brings to mind the romantic sight of bees or hummingbirds flying from flower to flower, speckled with pollen. But the process can be much more dramatic than this, as is the case with the Dichaea cogniauxiana orchid species. Female beetles of the Montella genus, just 2 mm in size, visit the orchids and transfer pollen from the male organ to the female organ of the same flower. They then lay their eggs in the flower, where the larvae are born and devour the fruit—formed thanks to the fertilizing action of the mothers—seeds and all, and the orchid loses its chance to reproduce. In five years of observation, researchers from the University of Campinas (UNICAMP) found that one-third of the fruit infested by these beetles was rescued by parasitoid wasps, which killed the beetle larvae. In these cases, the orchid fruit developed normally, according to a study that was conducted as part of biologist Carlos Eduardo Nunes’s PhD at UNICAMP, supervised by Marlies Sazima (Current Biology, March). The researchers believe that this system compensates for cases where benign pollinators are rare. With the help of the wasps, the orchids pollinated by the beetle are actually more likely to produce viable seeds than those not visited by the insects.