P. algidus is 13–28 mm in length with females usually larger than males and in some areas it is a mainly black wasp with a red spot on the metasoma.

The wasps were observed to switch from Nephila clavipes in July to Parawixia sp., Argiope argentata and Araneus sp.

The wasps hunted by actively walking on the surface of the vegetation, intermittently flicking their wings, but stayed in the outer layers of leaves and did not enter into deeper cover.

Her digging activities got faster as she neared completion of the burrow, occasionally interrupting her efforts to inspect and move the prey.

To move the prey, it was dragged backwards over the ground and under the vegetation while the wasp held it by the base of the hind femur.