vertical diving beetle

Vertical diving beetle is a large predaceous diving beetle. It occurs in the United States from Maine to Virginia, west to Minnesota, and in southern Canada from Nova Scotia west to Manitoba.

Adults are active from March to November. They are found in eastern deciduous forests, mostly in permanent ponds but also sometimes in temporary ponds. The larvae are aquatic. They prey on immature amphibians.

Adults are 1 3⁄16″ to 1 7⁄16″ (29.6 to 36.0 mm) in length. The body is elongated oval and broadest near the middle. It is streamlined, convex both above and below. It is dark brown or brownish black with yellowish markings and rarely with a greenish cast.

The head is large, and it is inserted well into the thorax. The eyes are large, and the inner margin is not indented. The antennae have 11 segments. The upper part of the face, corresponding to the forehead, is brown. There is a reddish to yellowish chevron in the middle, and a reddish to yellowish mark above the base of each antenna. The chevron can be distinct to barely visible, but it is always present. The plate on the face above the upper lip (clypeus) is yellowish. The mouthparts are yellowish to reddish brown, and they are directed forward.

The plate covering the first segment of the thorax (pronotum) is wider than long and is wider at the rear than at the front. There is no ridge (carina) in the middle, and the lateral margins are not flattened (margined). There is a broad yellowish stripe on each lateral margin, but there is no stripe on the front and rear margins. The front corners of the pronotum extend forward as rounded lobes on the sides of the head. The triangular plate (scutellum) between the bases of the wing covers (elytra) is small but visible.

The elytra are widest just beyond the middle and rounded at the tip. Unlike most Dytiscus species, they are smooth on both sexes. On other species, the elytra on some or all of the females are distinctly parallel grooved. The color is brownish black to black. There is a broad yellowish stripe on each lateral margin. The lateral stripes continue almost to the tip. Near the tip, there is an oblique yellowish line extending from the lateral stripe rearward and toward, but not reaching, the inner margin. The oblique lines vary from distinct to barely visible, and on some individuals, they are not visible. The underside of the abdomen is brownish to reddish.

The legs are short and broad. The fourth leg segment (tibia) has two spurs at the tip. The last part of each leg (tarsus), corresponding to the foot, has five segments. On the front legs of the male, the first segment of the tarsus is greatly enlarged. It has two large disks and many small disks that are used to grasp the female during mating. On both sexes, the tarsus on the hind legs is greatly enlarged and is fringed with hairs that aid in swimming.

Total length: 1 3⁄16″ to 1 7⁄16″ (29.6 to 36.0 mm)

Permanent and temporary ponds in deciduous forests

One generation per year: March to November

Immature amphibians.

Sources

24, 29, 30, 82, 83.

Common

This is on our front porch - we live about a 1/2 - 1 mile from where the Mississippi exits Lake Bemidji.

Kristen O’Leary
10/8/2024

Location: Bemidji, MN

This is on our front porch - we live about a 1/2 - 1 mile from where the Mississippi exits Lake Bemidji.