Philodromus cespitum is a species of running crab spider in the family Philodromidae.

Philodromus cespitum is a foliage-dweller, and is the most abundant species found in European fruit orchards.

A diurnal ambush hunter, it preys on aphids, insects, and occasionally competitor spider species.

Sympatry occurs between P. cespitum and P. fuscolimbatus in the northern Alps, a region where the two species overlap.

[3] Philodromus cespitum is a foliage-dweller,[8] and is the dominant species found in Central European fruit orchards.

Both sexes show locomotor activity indicative of a twenty-four hour circadian rhythm cycle.

However, the exact effect of these circadian rhythms on locomotion differs between males and females.

They sometimes engage in intraguild predation, in which they feed on competitor species as well as smaller prey.

However, since the costs are high due to retaliation and risk of injury from the competitor spider, intraguild predation does not often occur.

[14] Foraging aggressiveness in P. cespitum can sometimes lead to overkilling, where the organism kills more prey than it can consume.

Males who have a proportionally larger femur length in comparison to the females they are courting perform more taps than mating pairs who have a more similar ratio.

The male pursues the female until she stops moving and then taps continuously as he climbs over her body.

The male then enters the mating position, in which he faces towards the tip of the female’s opisthosoma.

Since they do not have a complicated shape or structure, genital plugs are low cost for the male to produce.

Plug size and quality are positively correlated with the number of times that the male taps the female’s body during courtship.

Females may determine the amount of plug material that a male deposits by choosing when to end the copulation.

Philodromus cespitum exhibit abnormal web-building behaviors prior to the emergence of the larva parasite.

[19] Philodromus cespitum acts as a biological control agent by feeding on pests in fruit orchards.

[9] Because fruit orchards are one of the main habitats of P. cespitum, they are affected by the insecticides sprayed against the pests that they consume.

This may be due to an impaired sensory system, taste, or mobility as a result of the insecticides.

This may be due to reduced prey availability or behavioral changes as a result of altered internal states or gene expression.