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Group 6

Born a thief: flower fly larvae steal sundews' prey

Wiki site of the practical exercise of the IX Southern-Summer School on Mathematical Biology.

Here you will find the exercise assignment and the group's products.

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Although little is known about the biology of Toxomerus basalis, a species of flower fly (Syrphidae), a recent discovery helped to elucidate it's habits at the larval stage. Larvae of T. basalis were found feeding on prey captured by the traps of some sundews (Drosera spp.), a genus of carnivorous plants which catch its prey by secreting a sticky substance called mucilage. As the larvae have been observed to move freely through the sticky traps, they are thought to have adaptations which prevent them from becoming trapped and also from being affected by the digestive enzymes of the sundews.

www.scienceticker.info_wp-content_uploads_2016_05_toxomerus_basalis_400.jpg This constitutes a kleptoparasitic interaction: when individuals of one species steal food itens gathered from individuals of other species. Although difficult to quantify, this interaction may affect negatively the sundews, diminishing their reproductive potential or even killing individuals.

On the other side, since it is thought that the kleptoparasitic interaction is obligatory for T. basalis, and because syrphid larvae are known to have low dispersal capacity, then the choice of oviposition location by females is very important. Although T. basalis females have not been observed during oviposition, it is thought that they land directly on the sundews to deposit their eggs, making them vulnerable to getting stuck on the sticky traps.


Build a mathematical model that incorporates the effects of the kleptoparasitism by the larvae and the carnivory of adult flies by the sundews.

Suggested questions

  • How susceptible to the lack of nutrients from prey need the sundews be for the kleptoparasitism to threaten its population persistence?
  • How does the retention capacity of the sundews' mucilage affects the flower flies? On the one side, a strong retention means more prey for the larvae to steal, while at the same time it means more adult flies getting caught.
  • How does the theft intensity, either by the population size of the flies or by the stealing efficiency of the larvae, affects the system? How does it relate to the susceptibility and the retention capacity of the sundews?

Further well-grounded questions from the group are welcome.


Fleischmann, A., Rivadavia, F., Gonella, P. M., Pérez-Bañón, C., Mengual, X., & Rojo, S. (2016). Where is my food? Brazilian flower fly steals prey from carnivorous sundews in a newly discovered plant-animal interaction. PloS one, 11(5), e0153900.

2020/groups/g6/start.txt · Last modified: 2020/01/10 19:59 by prado