The most compelling trait used to differentiate adult members of the family from its close relatives, the elaterids is how the second antennomere is placed on the basal segment.

Eucnemid beetles will have the second antennomere placed subterminally (off set to the side) from the first one.

Elaterid beetles will have their second antennomere placed at the terminal end of the first segment.

Other traits used for identifying eucnemids from elaterids include the lack of a free labrum and the anterior margin of the prosternum being straight rather than lobed. The anterior margin of the prosternum should not be used as definitive means to separate the two families, since primitive members of Eucnemidae will have that lobed anterior margin of the prosternum much like Elateridae.

LARVAE-

Often referred to as wireworms and cross-grain borers. Four larval forms exist:

Buprestiform -- Larvae are not heavily armored. They are less sclerotized. They are often whitish in color with a well expanded prothoracic segment, much like the larvae of Buprestidae. These larvae will also have extremely small mandibles with outwardly projecting teeth. Some larvae will have some velvety patches on the surface of the segments and also will have elaborately shaped scleromes on the prothorax in the shape of a "T" or an inverted "L".

Elateriform -- Larvae are heavily armored or sclerotized. They are usually yellow-brown in color, wire-like in form and similar to larvae of Elateridae. The best way to identify these larvae from other families is to look at the highly modified head under magification. These larvae will have lateral teeth on the outside edge of the head capsule. Their mandibles are extremely small with outwardly projecting teeth. The surface of each segment will be covered with velvety patches called microtricial patches.

Fusiform -- Larvae are usually not heavily armored. They are often whitish in color with well expanded segments, similar to a hymenopteran or dipteran larval types. Head capsules are either simplified and fleshy or armed with four to six anteriorally projecting teeth. Mandibles are not present, but possess a buccal region with labial and maxillary palpi. Larval types are primarily found in the tropics, but in case of the Nearctic region, may be present in two possibly three pantropical genera.

Onisciform -- Larvae are heavily armored or sclerotized as in the Elateriform larvae. Colorations are similar as well. The larval form is generally flatter, with wider than long thoracic and abdominal segments. The best example of this form is the Dohrn's Elegant Eucnemid Beetle in Southern California.

Range

All continents except for Antarctica; most diverse in the tropical and subtropical regions

Habitat

Found largely in woodlands and forests, especially with a diverse forest structure and plenty of dead wood for breeding. Adults are found in the tree canopies and on/under tree bark. Larvae are either in moist dead wood, hard seasoned wood or thrive in the soil near the roots of dead/dying trees. Fungi are usually present in those situations where larvae have been found.