Kieran and I spent several hours exploring Alameda Creek in Sunol Regional Wilderness on Friday afternoon. The creek is large enough to flow year round, even when there’s a drought. We caught a large, grumpy crayfish, probably Pacifastacus leniusculus, and a couple of whirligig beetles. But the most dazzling display of all was the beautiful, metallic colored damselflies zooming everywhere above the water. We observed hundreds of gorgeous American Rubyspots (Hetaerina americana) and lovely blue Vivid Dancers (Argia vivida). This time of year the aquatic damselfly nymphs crawl up on riparian vegetation and the imago emerges from the nymphal shell. The exuvia is left behind — a shell in the shape of the nymph. When damselflies mate, the male grabs the female behind the head with the tip of his long, flexible abdomen, and she bends her own abdomen up to touch his. This awkward-looking position is called the “wheel.” The females lay their eggs on underwater plants, sometimes completely submerging themselves (and their mates!) in the process.

Hiking in Alameda Creek

Hiking in Alameda Creek in Sunol.

damselfly, argia vivida, sunol, alameda creek

Argia vivida.

Argia vivida side view

Argia vivida, the Vivid Dancer.

damselfly, hetaerina americana, sunol, alameda creek

Hetaerina americana, the American Rubyspot. The males use the bright red patches on their wings to attract mates.

damselfly, hetaerina americana, sunol, alameda creek

A male American Rubyspot damselfly.

whirligig beetles, sunol, alameda creek

Whirligig beetles.

Exuvia

The exuvia, or cast-off skin of a damselfly.

queen ant, sunol, alameda creek

A winged queen ant, caught in a spider’s web after her nuptial flight.

queen ant, sunol, alameda creek

A queen ant, rescued from a spider’s web above the creek.

Pacifastacus

A large, grumpy crayfish.

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