Paper of the week (50)

Wise MJ, Kieffer DL & Abrahamson WG (2006) Costs and benefits of gregarious feeding in the meadow spittlebug, Philaenus spumarius Ecological Entomology 31: 548-555.

Ecological Entomology is definately my favourite entomological journal, and almost all issues contain some papers worth reading.
The selected paper is about optimal group size in a spittlebug which feed gregariously in shared spittle masses. The authors performed glass house experiments in which group size was manipulated. They found a negative correlation between group size and survival, suggesting that the insects were competing for limited plant resources. However, adult mass, which also is an important fitness parameter, showed a much more interesting pattern, being highest in intermediate group sizes and much lower at both low and high spittlebug densities. One explanation for the lower fitness of solitary individuals may be the difficulty to draw xylem against the negative pressure at which xylem is transported in the plant. Other possible explanations for the reduced fitness of solitary individuals were also presented, and they were all dealing with the difficulty for singles to overcome the physical and chemical defences of the plant.
The results suggest that the insects should display at least a slightly clumped dispersion, but that the benefits of group feeding saturate relatively fast, so that overcrowding should be avoided.

In conclusion: This is a nice and interesting paper which doesn't demand a lot of brain power to read. Have a cup of tea and read it when you need a break.