Ismarinae is a subfamily of wasp

Wasp

The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...

s belonging to the family Diapriidae

Diapriidae

Diapriidae is a family of insects belonging to the order Hymenoptera. These tiny wasps are typically parasitoids on the larvae and pupae of a wide range of insects, especially flies; a few are hyperparasitoids...

, containing only the single genus Ismarus. There are approximately 30 species known in this small relictual group, all of which appear to be hyperparasitoids that parasitize Dryinidae

Dryinidae

Dryinidae is a family of hymenopteran insects with about 1,400 described species found worldwide. These are solitary wasps whose larvae are parasitoids on other insects. The only known hosts are Hemiptera, especially leafhoppers....

 (that attack leafhopper

Leafhopper

Leafhopper is a common name applied to any species from the family Cicadellidae. Leafhoppers, colloquially known as hoppers, are minute plant-feeding insects in the superfamily Membracoidea in the order Hemiptera...

s).

Ismarines differ from other diapriid wasps by lacking a facial projection from which the antenna arise, and characterized by various degrees of fusion of the metasoma

Metasoma

The metasoma is the posterior part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory system, and circulatory system, and the apical segments are typically...

l terga

Tergum

A tergum is the dorsal portion of an arthropod segment other than the head. The anterior edge is called the base and posterior edge is called the apex or margin. A given tergum may be divided into hardened plates or sclerites commonly referred to as tergites...

.