Spiders eat together and stay together

UBC zoologists have recently discovered that the ability to work together to catch large prey has allowed spiders to live in the flock to expand the law of nature to reach a giant herd size.

The findings are published in this week's issue of the Proceedings of the National Academy of Science. It will explain why the spiders live in the tropics and thrive in the tropics, but their herds shrink as latitudes as well as altitudes increase.

Leticia Avilés - lead author and assistant professor of Zoology, UBC - said: 'The size of the organism seems to be confined to the rate regulation that scientists call' surface ratio and volume''. While organisms often have an energy demand that is directly proportional to the volume, they acquire nutrients through the surface.

'As the organism grows, its surface ratio and volume decrease. This is the way that nature controls the size of different species'.

The same rule can be applied to the herd. The surface area of ​​the three-dimensional spider web that the spiders live in to catch the lip usually does not grow as quickly as the number of spiders in the nest. Therefore the number of prey for each spider decreases with the size of the herd. But the spider Anelosimus eximius - a spider that lives in society is famous for its huge population . Some spiders have up to 20,000 individuals. They have gained the ability to expand the laws of nature by working together, so the number of insects they catch is significant when the herd grows.

Anelosimus spiders live in large groups to work together to catch insects of much larger size than them.

Avilés has studied wild spiders in the Amazon Ecuador with student Eric Yip and graduate student Kimberly Powers. Avilés said: 'The average size of prey caught increased 20-fold when population size increased from less than 100 to 10,000 spiders'.

'So even if the number of prey drops sharply when the population grows, the biomass that each spider gains actually increases'.

The study also found that large prey, while constituting only 8% of the spider's diet, contributed up to 75% of the dietary needs of the herd.

'But this only has a certain meaning'. Avilés adds that the biomass of the prey that the spiders consume peaks when populations range from 500 to 1,000 members.

Because Anelosimus spiders live in colonies that are rarely seen in latitudes and high altitudes, he must be 'these regions do not have enough large-sized insects to maintain the aforementioned hunting behavior ', Avilés said. expression.