Biodiversity

Thursday, April 27, 2006

INSECT ATTRACTION

How do insects attract a mate? Different insects use different strategies and what seems attractive to one group goes unnoticed to another. But they all serve the same purpose: to find a mate and complete their life cycle. Here are a few examples of the diversity in attraction methods that have evolved from colour, to smell to sound.

Butterflies and moths are the adult stage of a group of insects called the Lepidoptera. The sole purpose of this stage is to find a suitable mate, sexually reproduce and secure the maximum amount of offspring. There is no simple distinction between moths and butterflies, but generally moths are mostly nocturnal and their larvae construct intricate cocoons to protect the pupae. The wondrous colours of most butterflies and some diurnal moths are produced by small scales that cover the wings and body. “These scales have pigments that produce the white, red, yellow and orange colours with the brighter metallic and iridescent colours being produced by fine grooves and ridges on the scales that diffract light.” (1) In some species the males have modified scales in the form of long scent hairs that release chemicals to attract females during courtship.(1) This is a species specific communication, where females respond only to the chemicals release by males of their own species. (1)

Wing patterns and colours in butterflies play a role in attracting a mate. In some species the specific wing patterns allow a mate to recognize a partner of the same species. (2) In others it seems that the brightness of the colours influences the selection of a mate. (3) Some species have ultra-violet reflecting colours which indicate their sex allowing females to recognize a male and males to recognize each other. (4) Polarized light for mate recognition is used by some species of butterfly that inhabit deep forests where lighting can be tricky. (5) But is not only colour that is used to attract the opposite sex. Many butterflies perform elaborate courtship displays to attract females.

Moths use pheromones to attract each other. The sex pheromones are produced and released by the female moths to advertise their readiness to mate. These sex pheromones can be picked up by male moths over very long distances. They have thus adapted a “smell strategy” compared to the butterflies, who have perfected their “colour strategy”.

Insects in the order Orthoptera use sound as their attraction strategy. Grasshoppers and locusts produce sounds with special sound producing organs on their hind legs.(6) They do this by rubbing these special organs on their hind legs against the strong veins of their wings. Crickets and katydids have specialised sound organs on their wings.(6) With these organs the katydids produce a sound that sounds like “Katy did, Katy didn’t”, hence its name. (7)
Cicadas are of the order Hemiptera. The male cicadas also have specialized sound organs and are the master singers of all insects. These organs produce the sound through vibrating the membranes with the help of strong muscles. They have two hollow resonators in their abdomen that amplifies the sound, and some species have the capability of producing sounds exceeding an incredible 106 decibels.(8)

References:


1. Picker M, Griffiths C, Weaving A. 2002. Field Guide to Insects of South Africa. Cape Town: Struik Publishers. Page 314

2. Fordyce JA, Nice CC, Forister ML, Shapiro AM. 2002. The significance of wing pattern diversity in the Lycaenidae: mate discrimination by two recently diverged species. J. Evol. Biol. 15: 871–879.

3. Knüttel H, Fiedler K. 2001. Host-plant-derived variation in ultraviolet wing patterns influences mate selection by male butterflies. J. Exp. Biol. 204: 2447–2459.

4. Silberglied R, Taylor O. 1978. Ultraviolet reflection and its behavioral role in the courtship of the sulfur butterflies Colias eurytheme and C. philodice (Lepidoptera, Pieridae). Behavioral Ecology and Sociobiology 3: 203-243

5. Sweeny A, Jiggins C, Johnsen S. 2003. Nature 423: 31

6. Picker M, Griffiths C, Weaving A. 2002. Field Guide to Insects of South Africa. Cape Town: Struik Publishers. Page 74

7. Wikipedia contributors. Katydid [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 27, 02:10 UTC [cited 2006 Apr 27]. Available from: http://en.wikipedia.org/w/index.php?title=Katydid&oldid=50357634.

8. Wikipedia contributors. Cicada [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 27, 12:00 UTC [cited 2006 Apr 27]. Available from: http://en.wikipedia.org/w/index.php?title=Cicada&oldid=50409567.

Karen Marais

E-mail 2657211@uwc.ac.za

Web http://brit-journal.com/karen2006bcbnisl/

3 Comments:

  • the way the insects mate is different from us(humans)

    By Blogger lethabo, at May 15, 2006 10:28 AM  

  • Hey there

    Again, good work. On-topic, well-written, and a good spread of references consulted. No real complaints on my part.

    Nick

    By Blogger NcK, at May 17, 2006 2:00 PM  

  • Hi Karen

    I am really impressed with your work. "Insects in the order Orthoptera use sound as their attraction strategy," do not think there might be communication break down, you know some man, conclude according to the way the ladies dressed and they rape them, which is totally wrong?

    Maybe those insects might be using that sound as they way of celebration.

    Chao

    By Blogger Maleka Evelyn, at May 22, 2006 9:00 AM  

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