SIGNALS USED BY INSECTS TO ATTRACT A MATE FOR SEXUAL REPRODUCTION

Insect use sight, smell and sound for their courtship. A combination of any of the three or a single one is used by a particular group to achieve attracts members of the opposite sex.

Pheromones is a chemicals released by organisms to send a message to members of similar species¹. They serve different purposes like alarming other animals, marking territories, marking food trails, sexual attraction among others. Sexual pheromones are mostly produced by females indicting their availability for mating and this applies also for insects but males also produce pheromones to indicate what species they are¹. An example of insects that use pheromones are the moths which when produced will be detected by males using their feathery antennae which are large⁶.

Other insects make calls (noises) which attract members of the opposite sex and repel competing members of same species. The calls vary from species to species as they are produced differently. Male Crickets make calls known as chirp using their wings which have ridges that is more similar to a "comb and file" instrument. They achieve this by rubbing their wings or legs over each other, and the calls are conspecific (for similar species). This type of calls are for attracting females and repelling males (calling song) and are loud as compared to the courting song which is produced when the male is near a female and the sound is more quiet. The chirp sounds vary from species of cricket to the other and depend on temperature of the environment. The chirping in most cases is temperature dependent and is higher at higher temperatures and less in lower temperatures. This relationship between the chirping rate and temperature is described by a law known as Dolbear's Law.²

Cicadas and grasshoppers produce sounds just like the crickets do. Sound in grasshoppers is produced by rubbing the notched edge of the legs against the wings⁶. Sound is received by a membrane located between the two deep slits on the first thigh pair. Sometimes they use the visual display of their sometimes brightly coloured legs⁵. As for the cicadas the stomach has got two chambers. The inner wall of every chamber is stiff and pulled by a big muscle found in the stomach moving up to six hundred times per second and as it is pulled it makes a click. ⁶ The click (stridulation) is created is made loud in the abdomen “by a hollow vibrating plate and two hollow rectangular resonators and sound is received from eardrums on either side of the thorax of the cicadas” ⁶. Male cicadas are called tymbals and modulate their calls by moving their abdomens to and away from the tree that they sit on³. The sounds produced are different for each and every species hence its success and they can be amazingly loud. The different kinds of rubbing the body to produce sound are known as stridulation³.

Other species like the moths, butterflies and mayflies display their wings especially during the mating season. The wings are created in such a way that they have scales that have pigments and microscopic structures that split light reflect different form of light rays displaying different kinds of colours. These colours are conspecific and serve to attract species of the same species for mating. This members display sexual dimorphism (males having different colours and structure than the females). The displaying of colour is used during the mating season⁶.

References:

1. Wikipedia contributors. Pheromone [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 13:28 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Pheromone&oldid=51522169.

2. Wikipedia contributors. Cricket (insect) [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 14:55 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Cricket_%28insect%29&oldid=51531343

3. Wikipedia contributors. Cicada [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 19:47 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Cicada&oldid=51568000. .

4. Wikipedia contributors. Stridulation [Internet]. Wikipedia, The Free Encyclopedia; 2005 Sep 24, 16:53 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Stridulation&oldid=23924839.

5. Wikipedia contributors. Grasshopper [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 27, 13:10 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Grasshopper&oldid=50416744.

6. Knight, R. BCB Biodiversity chapter 2 The Swarming Hordes (Cited 2006 May 4) http://planet.uwc.ac.za/nisl/biodiversity/Chapter2/page_40.htm

VINCENT MUCHAI WAIRIMU

Biodiversity and Conservation Biology

University of the Western Cape

Private Bag X17 Bellville

TEL: +27825103190

Email: 2648463@uwc.ac.za

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