Chrysops frigidus has a small body compared to other deer flies. The front part of the head is yellow, the mouthparts are brown, and the antennae are brown or black. Their bodies are black and yellow. Their wings are clear with black or brown markings. Males have small differences in their antennae and mouthparts from females, and also have some darker areas in their wings than females. Some of these deer flies have much paler colors, but this is just a variety and they are still the same species.
The larva is 12 to 15 mm long, and pale yellow in color with a greenish tinge. The pupa is 11 to 12 mm long and light brown. (Teskey, 1969; Teskey, 1990; Thomas, 2009)
Chrysops frigidus is a deer fly found throughout Canada and Alaska and in the northeastern parts of the United States in New England. The most southern part of its range is the Rocky Mountains in Colorado. (Teskey, 1990; Thomas, 2009)
This deer fly is found in a variety of wetland habitats. It is most commonly seen in swampy woodlands. The larvae of the fly are also found in a wide variety of wetland habitats but have to live on a certain kind of moss. (Teskey, 1969; Teskey, 1990; Thomas, 2009)
Deer flies have complete metamorphosis and have the life stages of egg, larva, pupa, and adult. Before a female can lay her eggs, she must feed on blood from another animal first. She lays her eggs in moist sheltered areas. This species uses a special moss. Eggs hatch after about 5 days, and the larvae live in the moss. The larvae go through 6 stages called instars. This takes about 9 to 10 months. The larvae then move to a more protected position and become pupae, which lasts about 2 weeks. Adults normally emerge in the morning and their wings soon expand and harden so that they can fly away. ("Tabanidae The horseflies", 2002; Lake and Burger, 1980; Magnarelli and Anderson, 1977; Magnarelli and Anderson, 1981; Roberts, 1980; Teskey, 1969; Teskey, 1990)
Male deer flies fly around looking for females or sit on vegetation, chasing after any passing flies, including possible female mates. Mating likely happens in the morning when temperatures are cooler. Females likely mate at least two times during their lives. (Anderson, 1971; Catts and Olkowski, 1972; Goodwin and Drees, 1996; Leprince, et al., 1983; Teskey, 1990; Troubridge and Davies, 1975)
Before females can lay their eggs, they have to feed on blood from an animal. Four to eight days after the blood meal, females lay the fertilized eggs on the stems or underside of leaves above or near the moss that this species uses. The eggs are usually laid on warm, sunny days in the morning. Deer flies are good fliers and may move as far as 1 to 2 km from where they mated to lay their eggs. (Anderson, 1971; Catts and Olkowski, 1972; Goodwin and Drees, 1996; Leprince, et al., 1983; Magnarelli and Anderson, 1977; Teskey, 1990)
Females feed on the blood of other animals to be able to provide yolk in the eggs for their offspring. They also lay the eggs near the the moss that this species uses. The adults move on after the eggs are gone and provide no more parental care. (Teskey, 1990)
The lifespan of Chrysops frigidus is a little over a year, at most. Adults likely live for several weeks after emerging from pupation.
Deer fly females often gather in groups, especially when looking for an animal to feed on. They are very active and fly a lot, and can be seen flying around from late May to mid-September. They are the most active on warm, sunny days.
Females give painful bites to the animals that they are taking blood from. Because the bite is so painful, it is hard for the female deer flies to finish their blood meal before the animal brushes the fly away. So females have to take blood from several different animals, and they often spread diseases to the animals (and humans) that they bite. (Burnett and Hays, 1974; Krinsky, 1976; Teskey, 1990)
Deer flies can fly up to 1 to 2 km away from where they emerged and mated.
Deer flies use vision and detect chemicals to communicate with others, as well as to gather information about their environment. Males use vision to find mates, and females use vision to find animals to feed on blood from, and also to find places to find eggs. Females are attracted to chemicals produced by animal hosts. They are also attracted to sources of heat, which is one way that they find warm mammals to feed on. (Anderson, 1971; Catts and Olkowski, 1972; Leprince, et al., 1983; Mihok, et al., 2007; Teskey, 1990)
The larvae apparently feed on organic matter in moist soil. Adult males feed mainly on nectar, but also on pollen. Females feed on nectar as well, but also eat rotting fruit and a sugary-liquid called honeydew produced by insects in the order Hemiptera. Adult females feed on blood to produce yolk for their eggs. They feed on blood from deer, humans, cattle, sheep, hogs, horses and other domestic animals. (Lewis and Leprince, 1981; Magnarelli and Anderson, 1977; Magnarelli and Anderson, 1980; Magnarelli and Anderson, 1981; McAlpine, et al., 1981; Teskey, 1990)
Deer flies of the genus Chrysops have been recorded as prey for birds, amphibians, dragonflies, robber flies, and wasps (including Vespula, Crabro, and Bembix). (Teskey, 1990)
Chrysops frigidus males may pollinate the flowers on which they feed. They are also preyed upon by many other animals. Females are parasites and need to eat blood before they can reproduce. They feed on the blood of many large vertebrates, including deer, humans, and many domestic animals. The females can also transmit diseases to the animals they bite. These deer flies are also harmed by many different parasites. (Krinsky, 1976)
Deer flies are known as pests because the female will feed on the blood of certain mammals, including humans. Deer flies in this genus, Chrysops, are known to be able transmit diseases to the animals they bite, including anthrax, tularemia, anaplasmosis, hog cholera, equine infectious anemia and filariasis, and even Lyme disease. In North America, they do not cause many health problems for people, but their bites can be painful and annoying. They are responsible for causing disease in domestic animals and livestock, however. (Lewis and Leprince, 1981; Luger, 1990; Lyon, 2013; Magnarelli and Anderson, 1980)
These deer flies may help to pollinate some plants that humans use, but otherwise they are not helpful to humans. (Teskey, 1990)
Chrysops frigidus is not an endangered species.
Nicholas Gezon (author), University of Michigan Biological Station, Brian Scholtens (editor), University of Michigan Biological Station, Angela Miner (editor), Animal Diversity Web Staff.
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