Diptera- the true flies


Art by: C. Ruth Neudahl
Text by: Valerie Brady

Note the size of the real penny and use it to judge the size of the bugs in the following pictures.

Family: Chironomidae, Non-biting Midges

chironomid larvaAdult Chironomidae

Class: Insecta

Order: Diptera, the true flies

Family: Chironomidae, non-biting midges

Size: Larvae are 0.1 to 0.5 inch (3-10 mm) in length, a few reach 1 inch (25 mm) long

Habitat & Habits: Chironomid larvae occur in most aquatic habitats. Many larvae construct silk tubes within burrows or attached to immoveable substrates. Adults resemble mosquitoes without a proboscis; males have bottlebrush antennae; they do not bite.

Feeding: Most larvae eat detritus and algae, some eat wood. Tanypodinae larvae are active predators. Adults live a few days to a week and feed little if any.

Water Quality Indicator: In general, Chironomidae are moderately tolerant of nutrient pollution. However, some species are very pollution tolerant and some species are very sensitive.

Family: Culicidae, Mosquitoes

mosquito larva

mosquito adult

Class: Insecta

Order: Diptera, the true flies

Family: Culicidae, mosquitoes

Size: 0.25 to 0.5 inches (8 - 12 mm)

Habitat & Habits: Larvae ("wrigglers") generally live in still waters, and are occasionally found in backwater areas of streams. Larvae either remain at the surface or come to the surface for air. Adults are terrestrial.

Feeding: Most larvae sweep mouth brushes through the water to collect detritus and tiny organisms for food. Most adult females need blood to produce eggs.

Water Quality Indicator: Mosquitoes are not considered important water quality indicators.

Family: Simuliidae, Black Flies

blackfly larva
blackfly adult

Class: Insecta

Order: Diptera, the true flies

Family: Simuliidae, black flies

Size: Larvae: 0.1-0.3 inches (3-8mm), some larger

Habitat & Habits: Larvae use their "butt" hooks to attach to silk they spin on rocks in the current of streams and rivers. In good habitat, hundreds or thousands of larvae may cover stream rocks. Adults are terrestrial and live less than 3 weeks.

Feeding: Larvae hold their mouth brushes ("fans") in the current to filter out detritus for food. Adult females bite vertebrates for a blood meal. Their bites have been known to kill animals.

Water Quality Indicator: Larvae live in fairly clean water and are only moderately tolerant of pollution.

Family: Tabanidae, Horse and Deer Flies

horsefly larva
adult horsefly

Class: Insecta

Order: Diptera, the true flies

Family: Tabanidae, horse and deer flies

Size: 0.5-2 inches (11-55 mm); adults: 0.75-2 inches

Habitat & Habits: Larvae are found in streams, ponds, and marshes, especially along the edges.

Feeding: Most larvae are predators on small invertebrates; a few larvae eat detritus. Adults are terrestrial, and are strong fliers. Adult females need blood; they are persistent and have a painful bite.

Water Quality Indicator: Larvae are moderately tolerant of nutrient pollution.

Family: Tipulidae, Crane Flies

adult crane fly

Class: Insecta

Order: Diptera, the true flies

Family: Tipulidae, crane flies

Size: 0.5- 1 inch, up to 4 inches (10-25 mm, up to 100 mm)

Habitat & Habits: Larvae may be either aquatic or terrestrial, depending on species. Most aquatic larvae live in stream bottoms or among stream vegetation. Adults are terrestrial and resemble gigantic mosquitoes.

Feeding: Aquatic larvae may be predators, leaf shredders, or eat algae & detritus, depending on species. Adults do not bite.

Water Quality Indicator: Most larvae are intolerant or moderately intolerant of nutrient pollution, making them fairly good water quality indicators.