Emesaya brevipennis

Short-winged Thread-legged Bug

Emesaya brevipennis, thread-legged assassin bug



Family: Reduviidae

Subfamily: Emesinae

Length: 33-37 mm


Hagerty, McPherson, and Bradshaw (2001) studied the life history of Emesaya brevipennis in the field in southern Illinois and in the laboratory. They reported that the species is bivoltine in their study area, and that it overwinters in the egg stage.

Their study site consisted of a limestone rock face covered in poison ivy as well as trumpet creeper. Many of the bugs positioned themselves on the webs of a spider species, Anelosimus studiosus.

Mating in southern Illinois took place from late September to early November. The eggs were attached to the rock face, to spider webs, and to the vines. Eggs from the first brood began to hatch in early May, while the second brood started to hatch in mid-July.

Emesaya brevipennis preying on a Leafhopper

In the laboratory eggs hatched much more quickly than in the field, after an average of 34 days. From hatching through the five instars to the final molt to adult took an average of 56 days in the lab. Food for Emesaya brevipennis in the laboratory consisted of adult Drosophila pomace flies.

In 1909 H. F. Wickham published his "Notes on a Thread-Legged Bug" in the Ottawa Naturalist. Wickham wrote:

"In about twenty years of collecting at Iowa City, I had never met with a fully grown specimen of the wonderfully emaciated insect that goes by the name Emesa longipes. Therefore there was much rejoicing when my wife picked one up from a somewhat dusty corner of the bedroom floor...

"A neighbor living next door came to see me, bearing one of these curious beasts, which he had found crawling on his clothes. While we were sitting on the porch discussing previous finds, I holding this latest acquisition in my hand, he called my attention to another crawling along my arm. "I wonder if they fly," he said, but I replied that it seemed unlikely since the insect was so ungainly and the wings so very small in proportion, the thoracic segments showing none of the structure common to many small-winged insects of good flight.

"Scarcely had I made out my case, when another of the bugs came along in full flight, only two or three feet in front of our faces, and alighted on one of the pillars."

The following year Wickham wrote more about Thread-legged bugs. He was demolishing a dusty old shed and found many nymphs and adults of Emesaya brevipennis. He made notes on his observations and wrote them up for Entomological News, a publication of the Philadelphia Academy of Natural Sciences:

"Unless disturbed, the bugs were not seen to move much during the middle of the day, but towards the end of the afternoon they would come out and fly slowly and awkwardly through the lane between the trees, their long legs and slender bodies retarding their aerial progress despite the swift beat of the little wings. With the sun glinting against the coating of dust particles they made a curious and interesting sight, like nothing else that I have ever seen."

Hickman also observed mating, and captured the mating pair. The female began laying eggs two days after mating and within two more days had laid nineteen eggs in all. "The male died soon after, without, as far as I know, having resumed relations with his mate who used him as food and may have been responsible for his death." The female also died soon after, and Hickman closed his research note by saying that the hatchlings would be used to start a colony in his new shed (Wickham, 1910).

Mating pair, Emesaya brevipennis, Thread-legged Bug

Above: In this mating pair the female feeds on a moth while the male is positioning his body. The male has jack-knifed his body as his wings continue to stick out straight. Note how much smaller the male is compared with the female.

Map, Emesaya brevipennis

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American Insects site