Entomology - The life of insects

On this page will be described some of the insects that are common here in Sweden, what they look like, how they develop and of course how they live.

Mayflies - Ephemeroptera
The mayfly lives in freshwater, just like the caddis. At first it lives as a larvae/nymph under water for 1-3 years. The nymph has two or three long tail antennas and respires trough gills that point out from the body at the sides. The different species are specialized at different techniques of motion, those are swimming (Baetidae, Siphlonuridae), creeping (Heptageniidae), crawling (Ephemerellidae, Leptophlbiidae and Caenidae) and digging (Ephemeridae).

 The mayfly has a phase that is unique just for mayflies, it's called sub imago (dun). The sub imago phase occurs when the last nymph phase hatches into an insect that has wings and can fly. The sub imago is not sexually mature, it has to change skin first, and then it gets its true colour as an imago (spinner). At this stage, when hatching into sub imago, it is the most dangerous phase for the mayfly. If something goes wrong at the surface, and the nymph gets caught in its own shell and capsizes, it has no defence. These helpless insects, that are easily captured by predators, are called stillborns. When the mayfly dies, directly after the egg laying, it ends up on the surface with the wings laid straight out to the sides, the so called "Spent spinner". The imago has two pair of wings that are compound over the back when resting. The male mayfly has fore legs that are elongated, used to grasp the female in flight.
Imitations:
A "Gold Head Hare's Ear " imitates the nymph stage. When it is dead and has the wings to the sides, the "Mayfly, spent spinner" is a good imitation. Living mayflies are imitated with those flies named "Mayflies". Other good imitations are the Wulff flies.

Caddis flies - Trichoptera
The caddis fly lives as larvae in freshwater, either free living (Rhyacophilidae) or house building (Phryganeidae , Brachycentrus, Sericostoma, Notidobia and more). Some of those who are free living build capture nets in running water (Hydropsychidae, Philopotamidae, Polycentromidae and Psychomidae) while the house building live in shells from snails, gravel/sand, pieces of leafs etc. The caddis larvae are often easy to identify from other larvae's, but if you are confused over some larvae's that almost look the same, those might be mosquito larvae's. One characteristic is the two claws that are at the end of the body. The free-living larvae hatches, after a 2 -3 week pupae stage, by creating an air bubble and slowly drifting towards the surface where the skin cracks and the imago breaks free. During this transportation phase to the surface the free-living pupae is an easy prey for predators. Other caddis nymph tries to reach land before hatching. As an adult the caddis has two pair of wings that are laid as a roof (up-side-down V) over the body, and two long antennas that point forward. The imago can feed itself, and as such has a longer life span than the mayfly. The wings are one-coloured or speckled. Colours usually vary in grey, brown and black.
Imitations:
As a free-living larvae there is a fly that is named "Free living caddis larvae". When the caddis fly hatches free in the surface a "Klinkhamer" is a good imitation and so is the "Super pupae". Adult caddis, that flies above the surface, are sometimes imitated by for example "Nalle Puh (Winnie The Pooh)", E12 and different variants of "Caddis" 

Stoneflies - Plecoptera
The stonefly lives in running water, it has a flat and wide head, long antennas (at least half length of the body), two tail antennas and two pair of wings that are folded horizontally back over the body. The larvae's are predators and detritus-eaters, and can capture small fish brood. Stoneflies hatch directly from the larvae stage without stages pupae and sub-imago. The stonefly is a very early insect, it can crawl up on the edge of the ice in spring to walk or fly upstream and lay eggs. Finally, it should be stressed that because stoneflies depend upon cool, well-oxygenated water for their nymphal development, they are very susceptible to human abuse of water courses.
Imitations:
Yellow Sally (Isoperla grammatica)

Dragonflies - Odonata
The head is large, concave behind, on a flexible neck. The compound eyes are large and either widely separated. The Dragonfly has projecting facet eyes, short antennas, biting mouthpart and two pair of thin wings. They are predators and live on other insects, even small fish (brood) when they are larvae's. The Dragonfly also has a capture arm that is folded in under the head and is thrown out towards the catch when it is within reach. There are two different kinds of Dragonflies, the proper Dragonfly (Odonata Anisoptera) and the Damselfly (Odonata Zygoptera). All of them hold their wings folded back when resting, one of the largest Dragonflies has a wingspan of 75 mm. Damselflies are smaller than the proper Dragonfly. As they grow, larvae undergo approximately 10-20 molts, over a time between 3 months and about 6-10 years depending on species.
Imitations:
The well-known "Montana" imitates the larvae phase very well. 

Alderflies, dobsonflies, fishflies - Megaloptera
Adult fishflies and dobsonflies are generally nocturnal and secretive, while alderflies (Sialis lutaria) are diurnal. In Sweden the alderfly is the only fly interesting from a flyfishing point of view. When mature, the larvae leave the water and build a chamber under a rock or log, not too far from the aquatic habitat. In these chambers they spend several days as prepupae (generally about a week), then they molt and become decticous and exarate pupae which are capable of limited movement, including a strong defensive bite. After several more days the adults emerge and the life cycle is completed. Adults are short-lived (slightly more than a week) and generally do not feed, though they may drink water or sweet solutions. The adult alderfly remind of the caddis fly in a sense, since it has its wings folded in a similar manner. The wings are naked and shimmering brown with prominent streaks of brown.
Imitation:
Appropriate caddis flies.

True Flies / Mosquitoes / Gnats / Midges - Diptera
They are small, sometimes very small with big eyes, sticking or sucking mouth part and a pair of transparent wings. The Diptera's have a complete development cycle, they live as larvae, pupae and finally as a fully-grown insect. The larvae lack both head capsule and legs. They typically consume liquid food such as nectar and other plant exudates, or often decomposing organic matter. Usual species in Sweden within this family are the (Chrironomidae), the (Simulium) and the (Bibionidae). It's hatching in the surface with the head-part in the surface and the body hanging down. It is totally defenceless against the fish that often sucks in the hatching insect very carefully. It may seem like it's a very small fish, but often prove to be a big one.
Imitation:
As a hatching pupae it is possible to use the "Mosquito Klinkhamer".

Ants, bees, wasps, sawflies and horntails - Hymenoptera 
The Hymenoptera also have a complete development cycle, they live as larvae, pupae and finally as a fully-grown insect. This is called being a holometabolous (having a complete metamorphosis).  The first stage larvae lack legs, whilst the pupa have free appendages and developes into a cocoon before hatching. The adults or imagos have two pairs of membrane wings, except for work-ants, the hind wings are smaller than the fore wings which they connect to by a series of interlocking hooks. They generally have biting mouth parts sometimes also adapted for lapping and sucking. They are normally thin waisted to some extent and with a tail part often adapted for sawing and or piercing and stinging.
Imitations:
Balsa wasp. Black ant.

Cranefly Daddy long legs - Tipulidae 
One of the largest insects belonging to the two-winged species. The larvae is of little use for the fly-fisherman but the fully-grown insect can be very rewarding, mainly due to its size.
Imitations:
There are a large number of Daddy long legs imitations that will do.

Sow bugs and gammarus - Asellus and Crustacea
Mostly found in vegetation rich waters, lakes and slow running waters.
Imitations:
Corixa, a slow figure-of-eight retreive will do the trick.

Bugs and beetles - Coleoptera
The bug has a biting mouth part, facetted eyes and often antennas. It has a complete development cycle with larvae, pupae and adult insect. It has a panzer-like shell as an adult, the wings are folded under the shell while resting. Only a few are water living and then in freshwater. The larvae are soft and has often well developed legs and a movable body.
Imitations: