P. chrysidiformis is a medium-sized species (15–25 mm) that is the easiest recognisable Belgian species by the predominantly orange-red forewings. The transparent areas on the wings are small and the discoidal spot on the forewing is black. The black abdomen has 3 small white bands in the ♂ and 2 in the ♀. The rather hairy hind-legs are orange-red too as is the middle of the anal tuft. The latter is black at the sides. The proboscis is, as in all species of this genus, well developed and functional.
The males are fairly well attracted to a variety of different pheromone compositions but the one originally developed for S. myopaeformis appears to be more efficient than the other compositions . This species is best lured before noon but the optimal time span is very weather dependent.

The eggs are black and elliptically shaped.

The larva is off-white and has a dark-brown head with some lighter stains. As in all Sesiidae, the prolegs have a double wreath of small hooks.

The caterpillar makes irregular galleries in the root of the hostplant.

This species rarely constructs a cocoon but the red-brown pupa is often in a loose spun chamber at the upper part of a gallery at the transition zone between root and stem or in a stem-base itself.

The eggs are deposited on a stalk of the hostplant or on the upper- or underside of a leaf. The young larva initially lives just under the rind in a flat mine in the transition zone between stem and root. Later on, the caterpillars bore deeper into the root and make fairly long galleries. Initially, since the inside of the roots is yellowish, the frass is yellow but after a while it colours black. This way, infested roots are easily recognised because of the black colouration of these roots. For there are often several caterpillars in one root they can cause such substantial damage to the root system that it is not uncommon they kill the hostplant. After the hibernation, that takes place inside a root gallery, the caterpillars construct an exit gallery to the upper part of the root of in the lower part of a stem. Only occasionally a loose cocoon is constructed. Hence, the development completes in one year. Parasitism by flies (mostly Tachinidae) can be considerable. On hatching, the pupa works its way out through the cocoon and remaining thin bark layer.

The larva bores into the roots of several Rumex species (e.g. Rumex obtusifolius and Rumex sanguineus).

This species prefers xerothermic and not too wet biotopes such as road sides, waste places, embankments, ...