Why do Flies have Compound Eyes?
Just like a man woos the woman he loves, takes her to nice restaurants, buys her presents, and courts her to impress her before marriage, animals too choose their mates through courtship.
Since animals cannot do all these, they do it differently. Some animals put up a colourful display, while others give little gifts to their beloved – a choice worm, a designer nest and so on. A few species display their love through a series of grunts and others, like the Saurus crane or the stickleback fish, perform an intricate courtship dance.
Bowerbirds of New Guinea and Australia, create a small tower with twigs, shells, and flowers to attract the female and the tailorbird builds an intricate cocooned nest. Looking at nature’s numerous examples, one thing is quite obvious – impressing the other sex is quite a challenge.
Scientists have been studying the mating habits of animals and insects for years. Very few species can claim to have it easy. However, a recent study shows that the male houseflies have always had an eye out for the female of the species.
The eye of the fly is quite complex. Flies eyes’ are compound in nature – they contain as many as 28,000 light-sensitive structures called ommatidia (pronounced: om-ha-tee-dee-ya) grouped under the cornea.
The cornea in turn is composed of an equal number of hexagonal prism-shaped structures, each forming a separate image. The final image thus formed is actually like a mosaic image.
Compound eyes are only found in invertebrates (animals lacking a backbone). Entomologists (scientists who study insects) point out that compound eyes are adapted to spot swiftly moving objects, whereas simple eyes (the kind you and I have) are better adapted to see nearby objects and detect changes in light intensity.
The study reveals that specific region in the male fly’s eye helps them keep track of fast moving objects – a mechanism which they use to track female flies.
Unlike female flies, which generally glide along minding their own business, male flies are constantly on the look out for a partner. American scientists have named this specific region of the male fly’s eye, ‘the love spot’. They say that this region is enlarged to process incoming visual signals 60 per cent faster than females.
Since the cells of the ‘the love spot’ work much faster than those of female flies, male flies have an edge in zeroing in on potential mates.
However, whenever there is a good thing going there is a small catch, and for the male flies too the catch is that this specialised region in the eye consumes a lot of ‘metabolic’ energy.
Scientists theorise that since the male flies are not involved in laying eggs, the excess energy saved is put to use into other activities. Whereas in the case of female flies, they need to save up their energy to lay eggs.
The fly family can be divided into two major suborders – one consists of slender insects with long antennae, such as the mosquito and gnat, while the members of the other order, like the housefly, have stouter bodies and short antennae.
Flies make up one of the largest insect order for they contain about 80,000 known species and are found throughout the world, including Antarctica.
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