striped deer fly

Striped deer fly is a common, relatively small, deer fly. It occurs in the United States and southern Canada east of the Great Plains. It is especially common in the eastern U.S., where whitetail deer provide a plentiful food source. It is common, it is often abundant, and it is sometimes an annoying pest of humans in Minnesota. It can discourage visitors from visiting tourist areas. It has discouraged this visitor from entering the Boundary Waters Canoe Area Wilderness in early July, which is peak dear fly season.

Striped deer fly larvae are aquatic and predaceous, feeding on other insect larvae and on worms. Adults are active from June through August in Minnesota. They are found in open woodlands and wetlands, often near the margins of streams and ponds. Males feed on plant nectar. Females feed on the blood of mammals.

Males are relatively rare, and they are difficult to identify to the species level. Female adults are 5⁄16″ (7.5 to 8.3 mm) in length. The body is stout and reddish yellow with black markings. The wings have dark markings.

The head is broad, and it is covered with golden-yellow hairs. The compound eyes are bulging, iridescent, and brightly colored. On males they meet at the top of the head. On females they do not meet. There are three simple eyes (ocelli). The black area around the ocelli (ocellus spot) is broken up into three individual spots. Females have a large, bare, hardened area (frontal callus) on the front of the head between the compound eyes. The frontal callus is dull and reddish yellow with a dark upper margin. The antennae have three segments. The first segment (scape) is about 4 times longer than wide. The second segment (pedicel) is about two-thirds as long as the scape. Both segments are reddish yellow and are covered with short black hairs. The third segment (flagellum) is long, clearly ringed, and black, at least toward the tip. The large, bare, hardened area on the face (facial callus) and the small, bare, hardened area on each cheek (cheek callus) is reddish yellow. The mouthparts are modified for piercing flesh. The finger-like sensory mouthparts (palps) are reddish yellow.

The thorax is reddish yellow. On the upper side there ane three brown longitudinal stripes. On each side there is a brown stripe between the base of the wing ahd the shoulder (humeral) angle.

The abdomen is reddish yellow with 4 brown longitudinal stripes, 2 in the middle (middorsal stripes) and 1 on each side (lateral stripes). It has 7 segments (tergites). The first segment (T1) has two faint brown spots representing the middorsal stripes. On T2 the middorsal stripes are bold and the lateral stripes are faint or missing. On T3 through T5, all of the stripes are bold. T6 and T7 are black with a narrow yellow rear margin. The stripes on the thorax and abdomen are the features that give this species its common name.

The wings are clear with dark markings, including a dark leading edge (costa), a broad dark band in the middle (crossband) and a dark spot at the tip (apical band). The area between the crossband and the apical spot (hyaline triangle) is clear. Details of the extent and shape of these markings are important identifying features of species in the genus Chrysops. The dark markings are not broken by pale areas bordering the veins. The hyaline triangle is relatively large, extending beyond cell m1. The tip of the hyaline triangle reaches slightly beyond the fork of vein R₄₊₅. The apical spot fills more than half of cell r4. It usually extends into cell r5 but does not completely fill the outer edge of it. Cell cu1a is mostly dark. More than three-quarters of cell br is dark.

Total length: 5⁄16″ (7.5 to 8.3 mm)

Open woodlands, wetlands, the margins of streams and ponds

June through August

Larvae are aquatic.

Other insect larvae and on worms

Males feed on plant nectar. Females feed on the blood on mammals.

Sources

27, 29, 30, 82, 83.

Common and often abundant

Infraorder
Orthorrhapha was historically one of two infraorders of Brachycera, a suborder of Diptera. However, Orthorrhapha was paraphyletic, meaning that it did not contain all of the descendants of the last common ancestor. It was split into five extant (still existing) and one extinct infraorder. Orthorrhapha is now considered obsolete and has not been used in the last decade, but it persists in printed literature and on some online sources. A recent revision of the order Diptera (Pape, et al., 2011) revived the name Orthorrhapha, but this has not been widely accepted.

Striped Deer Fly
Cayman Mickler

Alfredo Colon
6/18/2024

Location: Albany, NY