I could not figure out how to identify Pagurus hirsutiusculus and Pagurus venturensis, so I scrutinized all 50,000 iNat hermit crab data and found a way to identify them both. Please refer to this page.
Basic characteristics of "Pagurus hirsutiusculus".
- The second antennae (longer) are brown with white stripes.
- cornea (eye) is black and white.
ocular peduncle (eye axis) thick and short, with black vertical lines.
The juvenile ocular peduncle is entirely red with a white longitudinal line.
- shield (back) is dark.
- a blue spot may appear proximal (knee) to the propodus (tibia) of the walking leg.
- distal portion (ankle) of propodus (tibia) of walking leg white, vertical line of propodus inconspicuous, entire propodus appears as a black band.
- The carpus (thigh) of the pedipalps is white as a juvenile, and the black band appears at maturity.
- prefer small shells that hide only the abdomen.
- The dactyl (finger) junction of the right cheliped is darkened and bordered prominently.
Basic characteristics of "Pagurus venturensis".
- The second antennae (longer) are brown with white stripes.
- cornea (eyes) light pink.
ocular peduncle (eye axis) elongate, brown or red.
Juvenile ocular peduncle may be entirely red with a pale white line.
- shield (back) is a bright color.
- distal portion (ankle) of propodus (tibia) of walking leg white with prominent vertical line on black band of propodus.
- The black bands on the carpus (thighs) of the gait legs are conspicuous even in juvenile stages.
- prefer shells with a wide horizontal shell opening.
- The dactyl (finger) junction of the right cheliped is white with an inconspicuous border.
Please point out any errors.
P.S.: Representative photos of Pagurus hirsutiusculus and Pagurus venturensis have been reorganized and replaced with photos that are easier to identify.
Pagurus hirsutiusculus
https://www.inaturalist.org/taxa/63219-Pagurus-hirsutiusculus
Pagurus venturensis
https://www.inaturalist.org/taxa/635130-Pagurus-venturensis