Beastie-hunt

Up the hill again tonight, this time with kids, a jamjar and a magnifying glass to capture and get a better look at one of those shiny black pencil-skirted bogflies. But by the time we'd gotten up there the wind was blowing up and the sun clouded over. Those exothermic invertebrates get sleepy and torpid under these circumstances, and laze in their camouflage instead of reacting. We got a hoverfly and a shieldbug by Dunstan's Loch

Ephemeroptera such as mayflies are comparatively easy to classify with magnification due to their absence of functional mouthparts and digestive system in their shortlived imago* state. They only live a few days in this adult, reproductively-capable form, but it's a pinnacle acheivement for any individual mayfly, its influorescence and goal. It comes after at least a year's gestation, metamorphosis from an egg to aquatic nymph to transitional dunfly to aerial mayfly. The adult mayfly who survives to reproduce is one in a thousand, its martyred siblings and now its angel-winged flight rare epiphenomena, and all to facilitate a simple admixture of genes.



Sub-adult stages of the mayfly


More mayfly-lore from http://www.roberth.u-net.com/Exopterygotes.htm- ignore the spelling for the detail.

Mayflies are the oldest of the winged insects and are unique in being the only known insect group which has a sub-imago* stage. This is a pre-adult stage which undergoes a final moult even though it has fully functional wings. The sub-imago stage is also called a "dun", whilst the imago is reffered to as a "spinner", being brighter and shinier than the sub-imago. Mayflies are associated with an aquatic environment, with the nymphal stages living in rivers and streams, and the adults which are found flying along waterways. The adult stage of mayflies is extremely short, often lasting for only a day, or even only a few hours. Adults have no functional mouthparts and there only purpose is to mate, which takes place on the wing after which the females may lay eggs in less than an hour. Their purpose fulfilled they quickly die. Eggs are laid in a variety of ways by females. Some scatter eggs singularly along streams and rivers, other lay their eggs in batches, whilst others actually crawl under the water surface, using emergent vegetation and lay their eggs directly onto water plants.

Nymphs vary in morphology according to the life strategy they use within the water. Nymphs either burrow in the river bed, these being cylindrical in shape. Crawl on vegetation, these nymphs are usually sturdy with strong legs and tarsi to obtain good purchase against the current. Some nymphs swim and are therefore very streamlined to aid passage through the water. Others live in the fast currents feeding on algae films and detritus which passes in the current. These nymphs are dorso-ventrally flattened and capable of clinging to rock surfaces against considerable forces of drag. Nymphs breathe using a series of gill filiments which can easily be seen extending from the sides of the abdomen. The gills are flat leaf like organs and house numerous tracheae into which oxygen from the water diffuses. There are usually seven pairs of gills and the nymph will often flick them periodically if placed in still water, this removes the oxygen deficient water immediately next to the gills and replaces it with more oxygen rich water. The nymphal stages are considerably longer than the adult stage. Ephemera danica takes two years to mature to the short lived adult stage. Some nymphs moult over twenty five times before becoming adults.

*Imago- defined as '2. (Zo["o]l.) The final adult, and usually winged, state of an insect.'