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Whirligig beetle (30)
Xplorer Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 125 W: 13 N: 327] (2187)
This is a group of Dineutus indicus Aubé, 1838 a species of Whirligig beetle.

This is a heavily cropped image. The workshop has another image which gives an idea of the location of these beetles and their peculiar behavior pattern. In the hot midday sun the group was place din the shadow of the rock..A few at the edges would be exposed to the Sun and would try to get on the inside in the shadow.

The whirligig beetles are a family (Gyrinidae) of water beetles that usually swim on the surface of the water if undisturbed, though they swim actively underwater when threatened. They get their common name from their habit of swimming rapidly in circles when alarmed. The Gyrinidae are surface swimmers for preference. They are known for the bewildering and rapid gyrations in which they swim, and for their gregarious behavior.

Interesting observation on group behavior from wikipedia:

The positions that individuals occupy within a group are determined by a number of factors, thought to include hunger, sex, species, water temperature, age, parasite level and stress level. Research underway on their behavior is directed at investigating the significance of chemical defense in relation to their position in the group. Such studies are of interest in research into aspects of nanotechnology because the beetles' motion may be expected to provide insights into how groups of robots might coordinate movements.

In particular the beetles make behavioral trade-offs that affect their choices of positions within a group. For example, relatively hungry beetles go to the outside of a group, where there is less competition for finding food, but higher risk of encountering predators. Males are also more likely to be found on the outside of groups (although grouping is not known to be relevant to mating behavior in this family). The economies that the beetles can gain by suitably adjusting their positions within the group, are important when individuals swim against the flow of a stream. By swimming behind other beetles they can take advantage of forward-moving drafts. Such action is called drafting. The determination of forward/backward positioning within a group has been found to be affected in a complex manner by a combination of water speed, sex of the beetle, and the type of predator (bird or fish) that a beetle has most recently observed.

Altered Image #1

Xplorer Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 125 W: 13 N: 327] (2187)
Whiligig Beetle Group Behaviour
Edited by:Xplorer Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 125 W: 13 N: 327] (2187)

This was the large group in which every individual was in continuous motion and jostling to be in the shadow.