Euspinolia militaris are solitary ectoparasites of mature larvae or pre-pupae of other insects, as is true of other mutillids, with females using the ovipositor to insert eggs into host brood cells, and for stinging (for defense). Like other mutillids, during mating the males are presumed to lift females and proceed to mate while airborne.
This species produces sound in response to threats from potential predators via stridulation, as do other mutillids, though this species is unusual in having a strong ultrasonic component to the sounds it produces.