Where is the Joy in a Fly? Sue Parker observes some adolescents with very limited prospects
Based on an article by Sue Parker in Algarve Resident, May 2017. Algarve Resident is the leading English-language newspaper and the source of essential information for Residents and would-be Residents in the Algarve.
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Ouch! A reverse blood transfusion performed by a female mosquito
Drat! Another mosquito bite... and like many people I react badly to these pesky insects. For some, the pain is short lived, a slight bump on the skin that itches for a few hours. Those less fortunate end up with weeping sores that persist for weeks.
In the Algarve, these minuscule vampires (it’s only the female mosquitoes that seek blood) are unlikely to cause serious illness - unless they arrive by plane and are themselves already infected with disease. Even so, wouldn’t it be nice if we could rid the world of these winged warriors and all other biting, stinging, bothering bugs. Who needs insects at all?
But of course, we do need insects. They pollinate most of our fruit trees and vegetables. A life without bugs would be impoverished in other ways, too. Many of our lovely songbirds feed on insects, and so do bats. Dreaming on, let’s be selective. Imagine a world without insects that sting. We would have to make an exception for bees, of course, for the sake of the fruit and veg (and yummy honey). Oh, and wasps get a pardon too, because some of our loveliest wild orchids are pollinated only by particular kinds of wasps. Okay, so maybe we just reinvent the world without aquatic insects – no mosquitoes, no ‘No See Um’ biting midges. Malaria and Dengue Fever? Vanquished. Zika virus? No worries! What’s the down side?
Nymph of the mayfly Ephemera danica
Well, there would be no food for small amphibians and reptiles, so in turn a famine for many bigger birds and mammals. There are even one or two wetland plants that supplement their meagre rations by snacking on flies. From Pete Seeger’s song Turn, Turn, Turn (via Ecclesiastes) we get, “For every thing there is a season, and a time for every purpose under heaven.” That must include aquatic insects. So where is the joy in a fly?
Mayflies, insect order Ephemeroptera, are joyful waterside sights. Years ago they were known as ‘dayflies’, which seems a more appropriate name: you can see them in every month of the year, and yet an individual mayfly can have an adult lifespan of just a single day. One of the largest mayflies, Ephemera danica, is sometimes referred to, confusingly, as The Mayfly. In Northern Europe this fly is most plentiful in the month of May, but even there some sentinels show up in March or April while late developers defer their debutante ball until September or even October.
A female mayfly dun
A female mayfly (there are 369 European species) lays her eggs in a freshwater lake, pond, river or stream. The eggs soon hatch into a tiny wingless insects known as nymphs. From then on those aquatic insects have but two aims in life. The first is to avoid being eaten (most fail), and the second is to eat enough dead leaves, algae and micro organisms to grow big and strong.
A nymph of Ephemera danica takes a year or sometimes two years to reach full size (about 2cm long). With no inner skeleton, its internal organs grow continually until they burst the skin (exoskeleton); then the nymph sets about growing a new, larger exoskeleton. This process is repeated many times, rather as growing crabs shed carapaces.
There comes a special day in the life of our aquatic chum, when it swims to the surface and its last nymphal shuck bursts. Out crawls a drab insect with wings and with tails much longer than those of the nymph from which it emerged - one of Nature’s conjuring tricks, but for our mayfly not quite the last.
Mayfly spinner - male
Flying into a waterside bush, the adolescent mayfly dries itself in the sunshine (or more slowly under a leaf if it has chosen a wet wedding day). Watch if you can as the mayfly moults yet again. Slowly a more beautiful insect emerges, leaving a flimsy dull shuck to blow away on the breeze. Not only are its wings now translucent and sparkling, but the legs are longer and those tails have more than doubled in length. This is the adult, known as an imago or spinner, and now is the time for its sole purpose under heaven: to breed. Swarms of mayfly spinners dance above the water, mating in flight before the females release the next generation to begin the whole process again.
When we sit by water on a sunny afternoon and watch the nuptial dance of mayflies, we are witnessing something that fossil records tell us dates back more than 300 million years – long before there were any dinosaurs. The dance will go on even when our planet is unable to support human life.
Meanwhile mosquitoes continue to make us dance, as the search continues for the perfect bug spray. So far, no joy!
