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Artwork by: Joann Wheeler 2001
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Fast Fact:
Stoneflies are often biological indicators of
water quality because they require highly oxygenated water for respiration. As a result
these macroinvertebrates are labeled "Sensitive to Pollution" and their presence
in a water system typically indicates good water quality. |
| Size |
12.7 to 38.09 mm, 1/2
to 11/2 inch |
| Habitat |
Stonefly larvae are typically crawlers. Larvae
are weak swimmers when forced to swim and do so by undulating their abdomen back
and forth (similar to how fish move in water). Larvae inhabit the benthic areas of
streams, lakes and rivers seeking cover under leaf debris, fallen trees and most commonly
under rocks. |
| Reproduction |
Stoneflies are a hemimetabolous order (Egg, Larva,
Adult) with all species having aquatic larvae. When stoneflies have metamorphed
into their adult form, mating will most often occur in nearby trees. In several species
males will crawl around and create a drumming noise with abdomens to aid in finding a
mate. After mating, females return to the water to deposit eggs. There are several methods
for depositing eggs and it often depends on the species. Most females will touch the tip
of the abdomens to the surface of the water while flying low. Upon contact with the water,
she will release the eggs. Others release the eggs while hovering over the water. Some
species will crawl into the water and deposit the eggs on top of submerged objects, such
as SAV. Larvae can take from six months to three years to fully develop. Once
developed, larvae crawl to shore and out of the water to dry off. Once the exoskeleton
dries and cracks, the adult climbs or flies away. The adult portion of the life cycle can
last two days to two weeks. |
| Feeding |
Some species are carnivorous and feed on
mayfly and dipteran larvae while others are herbivorous, feeding on algae and vegetative
detritus. As larvae develop and food sources change, stoneflies will "drift"
downstream in search of better resources/habitat quality. |
| Predators |
Fishes and other invertebrates feed on stonefly larvae. |
| Description |
Depending on species, stonefly larvae can be shades of yellow,
orange, brown or black and often appear two toned, such as black on the dorsal and
yellow-orange on the ventral side. Stonefly larvae can be distinguished from other
aquatic insect larvae by the two long hair-like tails and their elongate or flattened
shape. They have long antennae and if the gills are present they are located on the head,
thorax and/or abdomen. Oxygen is obtained from the water through the cuticle
or gills and most larvae are only found in oxygen rich waters. The adults are very similar
in appearance to the larvae, except that the adults have two pairs of net-veined wings
that can fold flat. |
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