Pterostichus niger above. This is a preserved specimen of a female adult. The adult body length ranges from 15 - 21 mm, it is often found under bark or rotting wood on all kinds of soils except the very dry, and hunts mainly at night. It is seen from spring to autumn, but most commonly in August and September.
It is common throughout the U. K. and Europe, and is also found in North America. Note that it is entirely black except for the last few segments of the antennae.
Pterostichus madidus, above, has the typical ground beetle body shape. If you look at Pterostichus niger above you will see that they differ considerably in the shape of the thorax.
Madidus has an adult body length of 14 - 17 mm, and its legs can very in colour from reddish to black.
It is very common in cultivated soil, gardens, woodlands, grassland and dry moorland. It is omnivorous.