northeastern hammertail

(Efferia aestuans)

Conservation Status
IUCN Red List

not listed

NatureServe

NNR - Unranked

Minnesota

not listed

 
northeastern hammertail
Photo by Mike Poeppe
 
Description

Northeastern hammertail is a common, “friendly”, medium-sized, robber fly. It occurs in the United States east of the Great Plains and in southern Quebec and Ontario Canada. It is the commonest robberfly in the subfamily Asilinae in the northeast.

Adults are active from May through September. They are typically found in grasslands, in sandy, dry areas, and around human constructions. They can be seen perched on trees, thickets fences, posts, and buildings. Unlike other robber flies, They often land on moving objects, including cattle and human beings. They are considered the most likely robber flies to land on humans.

Adults can be 916 to 1(14 to 28 mm) in length, but they are usually 1116 to (18 to 22 mm) in length.

When viewed from the front, the head is wider than high. There are two large compound eyes and three small simple eyes (ocelli). The compound eyes extend above the level of the top of the head (vertex), making the head appear hollowed out between the eyes when viewed from the front. They do not meet at the top of the head on either sex. The ocelli are arranged in a triangle on a prominent rounded projection (tubercle) in the middle of the head between the compound eyes. The face between the eyes is covered with hairs. There is a dense mustache of long hairs (mystax) at the lower margin. The mystax is mostly black but with many white or yellowish hairs below. The black hairs are stouter and bristle-like. There is also a cluster of forward-directed bristles (a “beard”) on the lower part of the face. The antennae are short and have 3 segments. The first and third segments are longer than the second. The third segment has a stiff bristle (arista) at the tip.

The thorax is broad, high, and only moderately arched. The upper side is covered with mostly yellowish hairs. The plate between the abdomen and thorax (scutellum) is swollen and it has 6 bristles on the margin, 4 black and 2 whitish.

The abdomen is long and slender. It is widest at the base and it tapers strongly to the tip, especially on the female. On the female, the sides and rear margins of segments 2 through 6 are covered with grayish, pollen-like dust (gray pollinose). The rear margin of segment 7 and the upper side of all segments are brown pollinose but appear black. The hairs on the upper side are short and black, while the hairs on the sides are yellowish white. The ovipositor sword-like and ¼ (6 mm) long. On the male, the sides of segments 2 through 4, the rear margin of segment 4, and all of segments 5 through 7 are white polinose. The genital bulb at the tip of the abdomen is black and very large. It projucts upward at about a 30° angle. It is as long as segments 6 and 7 taken together. The lower surface of the abdomen is covered with long white hairs.

The legs are stout and black. They are covered black and yellowish-white hairs, and they are armed with strong black bristles. The fourth leg segment (tibia) on each leg is mostly brown or dull red, black just at the tip. The last part of the leg (tarsus), corresponding to the foot, has five segments. The last segment has 2 pads.

The wings long, narrow, and clear, and they are tinged light smoky brown. The veins are brown. The first and second branches of the radial sector vein (R1 and R2+3) join before the end of R1 creating a closed cell that does not reach the margin. The first branch of the media (M) vein curves backward and ends far behind the wing tip. The subcostal cell is brown. There are 3 complete submarginal cells.

 

Size

Total length: 916 to 1(14 to 28 mm)

 

Similar Species

 
Habitat

Grasslands; sandy, dry areas; and around human constructions

Biology

Season

May through September

 

Behavior

Northeastern hammertail often lands on moving objects, including cattle and human beings.

 

Life Cycle

 

 

Larva Food

 

 

Adult Food

 

Distribution

Distribution Map

 

Sources

24, 29, 30, 82, 83.

9/14/2024    
     

Occurrence

Common

Taxonomy

Order

Diptera (flies)

Suborder

Brachycera

Infraorder

Asilomorpha

Superfamily

Asiloidea

Family

Asilidae (robber flies)

Subfamily

Asilinae

Tribe

Asilini

Genus

Efferia (hammertails)

   

Subordinate Taxa

 

   

Synonyms

Asilus aestuans

Asilus niger

Erax bastardi

Erax incisuralis

Erax tibialis

Nerax aestuans

   

Common Names

eastern hammertail

northeastern hammertail

 

 

 

 

 

 

 

Glossary

Arista

A large bristle on the upper side of the third segment of the antenna of a fly. Plural: aristae.

 

Femur

On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.

 

Mystax

On flies, especially in the family Asilidae, a patch of bristles or hairs (mustache) immediately above the mouth.

 

Ocellus

Simple eye; an eye with a single lens. Plural: ocelli.

 

Scutellum

The exoskeletal plate covering the rearward (posterior) part of the middle segment of the thorax in some insects. In Coleoptera, Hemiptera, and Homoptera, the dorsal, often triangular plate behind the pronotum and between the bases of the front wings. In Diptera, the exoskeletal plate between the abdomen and the thorax.

 

Tarsus

On insects, the last two to five subdivisions of the leg, attached to the tibia; the foot. On spiders, the last segment of the leg. Plural: tarsi.

 

Tibia

The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.

 

Tubercle

On plants and animals: a small, rounded, raised projection on the surface. On insects and spiders: a low, small, usually rounded, knob-like projection. On slugs: raised areas of skin between grooves covering the body.

 

Vertex

The upper surface of an insect’s head.

 

 

 

 

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northeastern hammertail
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Efferia aestuans, robber fly_2022
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Efferia aestuans, robber fly_2022
About

Female of Efferia aestuans, robber fly

 

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Other Videos

Huge Fly
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Jul 11, 2024

Huge Fly Northeastern Hammertail (Efferia aestuans)

 

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Mike Poeppe
8/5/2024

Location: near Houston, MN

northeastern hammertail
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Created: 9/14/2024

Last Updated:

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