Aquatic Insects Dayton Steelman Northwest Arkansas Master Naturalist
Aquatic Habitat Excellent Stream Site Here we find a variety of organisms with very different body shapes and ways of making a living. High biodiversity (or species richness) indicates a site with low human influence: most of the animals on this guide sheet should be present in a riffle sample. Several different types (or species) of stoneflies, mayflies, and caddisflies indicate a healthy site. More than one type of riffle beetle may also be identifiable, some are longer and skinnier than others. Some caddisflies are tolerant of degradation, so a large number of caddisflies does not necessarily indicate a good site, especially if they are the same species.
Moderate Stream Site The total number of different types of organisms (taxa richness) declines as degradation increases. About half to two-thirds the number of species found at an excellent site are found in a moderate site. The primary change from an excellent site is that there will be many fewer species of stoneflies. Mayflies will be present, but probably fewer species as well. Several types of caddisflies may be present depending on the type of degradation. The relative proportions of soft-bodied worms, Baetidae (family of mayflies), simuliid flies, or amphipods may increase. Beetles are probably still present; mollusks are not.
Poor Stream Site The total number of taxa will be low. Most of the taxa found are soft-bodied animals, e.g., fly larvae, oligochaetes, nematodes, and in very poor sites, leeches and planaria. Worms are often difficult to distinguish from each other because their shapes are similarly adapted to living in soft sediments. Stoneflies are absent entirely. The only mayflies present are probably Baetidae (a family of mayflies). Caddisflies may be present, but only a few tolerant types. Amphipods are often present. There may be a large proportion of a single type of animal. In general, animals present may be smaller than those found at an excellent site.
Orders of Common Aquatic Insects Found in Streams Stonefly (Order: Plecoptera) Mayfly (Order: Ephemoptera) Caddisfly (Order: Tricoptera) Dobsonfly (Order: Megaloptera)-rare Fishfly & Alderfly (Order: Megaloptera)-rare Dragonfly (Order: Odonta) Damselfly (Order: Odonta) Beetles (Order: Coleoptera) Butterflies/Moths (Order: Lepidoptera) True flies (Order: Diptera) Water Striders (Order: Hemiptera; Family: Gerridae)
Mayfly (Order Ephemeroptera) 2500 Species Mayfly diversity declines as streams are degraded; mayflies are particularly sensitive to mine waste.
The four stages of a Mayflies life cycle are; egg (Ovum, 1 to 3 weeks), Nymph (Nymphal 11 months to 24 months with 20-30 Moults), Dun (Sub-imago 1 to 4 days) and Spinner (Imago about 1 day). The eggs are deposited on or in water differently depending on the species. In some species the female will skim across the surface of the water in order to dislodge the eggs from her abdomen. Another species will fly across the waters surface and drop yellow or orange egg masses onto the waters surface. Some female mayflies will even use a protruding stem, leaf or other organic structure to crawl into the water in order to safely deposit her eggs at the bottom of the water column and others will actually dive into the waters surface in order to break the surface tension, then release the eggs underwater.
Dragonfly and Damselfly (Order Odonata) 6500 Species
Damselfly (Order: Odonata)
Dragonfly Life Cycle A male and a female dragonfly will mate while they are flying in the air. After two dragonflies mate, the female dragonfly will lay her eggs on a plant in the water, or if she can t find a suitable plant she will just drop them into the water. This portion of the dragonfly life cycle can take up to four years to complete, and if the nymph cycle is completed in the beginning of the wintertime, it will remain in the water until spring when it is warm enough to come out. Dragonfly nymphs live in ponds or marshy areas because the waters are calmer than in a stream or river. Sometimes they can be found in the calmer backwaters of rivers, too. Dragonfly nymphs may eat smaller dragonfly nymphs as they develop.
Damselfly Life Cycle Immediately after mating, the female will crawl down the vegetation, and 'into' the water to lay her eggs on the submerged portion of the vegetation. Most damselflies complete a life cycle in one year but some species take two years. The nymph will proceed through 10 to 12 "instars" or molts before becoming fully developed and ready to emerge as an adult. With each molt the nymph becomes somewhat darker in color. Finally the nymph will swim towards the shore and crawl up the shoreline vegetation. The damselfly nymph is very predacious.
Stonefly (Order Plecoptera) 2000 Species
Plecoptera (stoneflies) (2,000)
Water Striders - 500 species Hemiptera-True Bugs
Giant Water Bugs- 10 Species-Hemiptera There are two substrates of oviposition, females of species pertaining to the ancestral subfamily (Lethocerinae) oviposit on emergent vegetation. On the other hand, Belostomatinae females oviposit on the males' dorsum. The male will raise the eggs exposing them to air periodically to discourage the growth of fungus and maintain the viability of the eggs, or conduct a series of movements below the water known as brood pumping that increases the amount of oxygen diffusion.
Waterscorpion- 150 Species - Hemiptera Waterscorpions feed primarily on invertebrates, but occasionally take small fish or tadpoles.
Water Boatman- 525 Species-Hemiptera Habitat of Naiad: Ponds and slow moving streams. Habitat of Adult: Ponds and slow moving streams. Characteristics: They are mostly plant-eating insects but also eat small animals such as tadpoles. They swim right-way-up near the bottom. Like all aquatic bugs, water boatmen lack gills; they breathe air when at the surface of the water. They frequently carry an air bubble on their body surface or under their wings, and draw oxygen from this bubble while they are underwater.
Backswimmer 32 Species - (Order Hemiptera) They are predators and are up to nearly 2 cm in size. They are similar in appearance to Water Boatmen but are easily identified by swimming on their back and the modifications of their legs. They attack prey as large as tadpoles and small fish, and can inflict a painful "bite" on a human. They use a unique system to stay submerged: using the extra oxygen supply from hemoglobin in their abdomen, instead of using oxygen dissolved in the water. The size of these air bubbles, which provide buoyancy, changes as the nitrogen dissolves into the blood and the oxygen is used in respiration. This allows for regulation of the size of the air bubbles and their concentration of oxygen.[
Midges - 817 Species - (Order Diptera)
Caddisfly 1350 Species- (Order Trichoptera)
Although caddisflies may be found in waterbodies of varying qualities, species-rich caddisfly assemblages are generally thought to indicate clean water. Together with stoneflies and mayflies, caddisflies feature importantly in bioassessment surveys of streams and other water bodies. Caddisfly species can be found in all feeding guilds in stream habitats, with some species being predators, leaf shredders, algal grazers, and collectors of particles from the watercolumn.
Predaceous Diving Beetle 4000 Species - (Order Coleoptera) When hunting, they cling to grasses or pieces of wood along the bottom, and hold perfectly still until prey passes by, then they lunge, trapping their soon-tobe-food between their front legs and biting down with its pincers. Their usual prey includes aquatic insects, tadpoles and glassworms, among dozens of other smaller water-dwelling creatures.
Water Scavenger Beetles 260 Species - (Order: Coleoptera) The adults and larvae look like the Predaceous Diving Beetles. With rare exceptions, the larvae are predatory while the adults may be vegetarians or predators in addition to scavenging. Several species are voracious consumers of mosquito larvae, and other aquatic insects.
Rat-tailed Maggot (Order Diptera) Generally one species of rat-tailed larvae is found. It indicates a high level of animal manure is contaminating the aquatic habitat.
Black Fly Breeding Habitats Most species select aquatic habitats that have fast moving highly oxygenated water that is potable or almost potable however, there are species that are found in slow moving water in the south.
Black Fly -3 Species (Order Diptera) Eggs are laid in running water, and the larvae attach themselves to rocks and other submerged substrates. The eggs are commonly laid in batches of 200-300, in a range of 30 to 800, on objects in or near running water or directly onto water or on the surface. Eggs are either dropped directly into the water and sink to the bottom or are laid on emergent objects close to the waterline, where they are either directly wetted by water or are in the splash zone. Communal egg masses may be formed by several females ovipositing in close proximity, and there is some evidence that gravid females may be attracted to eggs laid by the same species, probably due to the presence of a pheromone. Females of several species crawl up to 15 cm below the water surface to oviposit on submerged substrates.