Black fly larvae characteristics and ecology

Black Fly Larvae

According to William F. Lyon at Ohio State University the scientific name for the black fly is "Simulium vittatum Zetterstedt, Simulium venustum Say, Simulium jenningsi, or Prosimulium sp." According to Lyon there are species of the adult black female fly that are "fierce biters, whereas others are strictly a nuisance by their presence around one's nostrils, ears, arms, hands, and other exposed skin areas." (2000)

TRANSMISSION of DISEASES

When the black fly bites the area will appear "as a small, red, central sport surrounded by a slightly reddened, swollen area." The bite will then become "itchy, swollen and irritating..." (Lyon, 2000) These flies are known to transmit a disease of "filarial worms, onchocerciasis" which can cause blindness and as well may transmit encephalitis. The following labeled Figure 1 is an illustration of the black fly larva (top) and the Pupa (bottom)

Black Fly Larvae and Pupa

Source: William F. Lyons (2000)

SPECIES: HABITS and LIFE-CYCLE

The different species of the black fly have life cycles and habits that are somewhat different from one another. The Simulium vittatum Zetterstedt species is known for pestering horses and cattle and can be found on a wide basis in North America. The second species or the Simulium venustum Say is one that bites fiercely and is distributed throughout New England and Canada. The third species or the Similium jenningsi is one that breeds in large rivers. The states of Pennsylvania and New England along with other states in the area are involved in a "biological larvicide" initiative to control the larvae's spread into the river and streams. The fourth species or the Prosimulium sp is one that is a bother in early spring and both swarms and bites with the larvae being found in smaller woodland streams. (Lyon, 2000) the following labeled Figure 2 illustrates the lifecycle of the black fly.

Lifecycle of the Black Fly

Source: Agriculture and Agri-Food Canada (2003)

III. LARVAE: SUSTENANCE and HABITAT

The young larvae "attach themselves to submerged objects" and molt six times while in the growth process. These larvae are "elongate with the hind part of their bodies swollen" and eat through use of a "head fan [which] sweeps food material into the mouth." (Lyon, 2000) These larvae stabilize their position in the water with "sucker-like discs and tiny hooks at the tip of the abdomen." They also are capable of spinning a type of thread to anchor themselves and may remain larva through the winter. According to Lyon: "Pupation occurs in a cocoon, open at one end. Adults emerge in two to three days when the water is warm. They are capable of immediate flight and mating. The entire life history spans about four to six weeks, depending on species, water temperature, available food, etc. There may be four generations per year." (Lyon, 2000)

IV. The LARVAE SPINS an UNDERWATER COCOON