April 18 | Hillsborough River: Swarms of the whirligig beetle (Gyrinidae spp.), in chaotic dance, gather in the sunlight on the still, black water of the Hillsborough River. Under canopies of ancient cypress, they roam its pools and eddies for prey, converging as a voracious pack on an upended dragonfly, a stray tent caterpillar—the remains of a fishing spider.

The beetle uses its mid- and hind-legs to propel itself along the surface (and sometimes below it) at some of the fastest swimming speeds in the animal kingdom1,2. In one second, nearly 60 strokes are completed, advancing the beetle upwards of 5 feet, or 120-body lengths. By comparison, the average Olympic swimmer completes about 1.6 strokes per second, advancing 6 feet—or 1.04-body lengths (based on average male height of 5 ft 9 in)3,4.


1. Thorp and Covish’s Freshwater Invertebrates, 4th ed. 2015. Ecology and General Biology.

2. Xu et al. 2012. Experimental studies and dynamics modeling analysis of the swimming and diving of whirligig beetles. PLoS Computational Biol: (https://doi.org/10.1371/journal.pcbi.1002792).

3. Fryar et al. 2018. Mean body weight, height, waist circumference and body mass index among adults in USA. US Dept. of Health and Human Services, US CDC. (https://www.cdc.gov/nchs/data/nhsr/nhsr122-508.pdf).

4. Rhett Allain 2012. Olympic physics: swimming, power and setting records, in Wired, Culture. Retrieved in August 2021 from https://www.wired.com/2012/08/olympics-physics-swimming/.

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