Catherine's writing reflects her life-long love of nature and gardening. She advocates for sustainability and respect for all living things.
Silkworm Moth "Flutterdance"
Tiny But Mighty
It is often said that insects will outlast us all, but how can such small creatures survive among larger and more aggressive predators? Let's take a look.
- Their small size allows them to go unnoticed.
- Insects are able to reproduce several times per season. Hot, humid weather can accelerate this process.
- Insects also become immune to controls as they adapt.
- Insects are masters of camouflage and mimicry.
Many species are equipped with irritating hairs or sharp spines to repel predators, especially in the vulnerable larval stage. Some, like Atlas moths and many butterflies, have bold markings or shapes which mimic larger and more dangerous stalkers. Others blend in with their environs, matching leaves or twigs like stick bugs, mantises, and katydids. The house centipede is an arthropod with a creepy deterrent. It will detach its legs which wiggle independently once dropped.
The Monarch butterfly caterpillar feeds exclusively on the milkweeds of the Asclepias family. The leaves of these plants impart a foul taste to the butterflies making them unpalatable to predators. Its toxin acts like an emetic, strong enough to make a blue jay vomit, and serves to teach avoidance.
The most sophisticated means of survival, however, comes from the use of naturally produced chemicals.
Meet Thomas Eisner
Thomas Eisner, reverently referred to as the Father of Chemical Ecology, left us a great legacy from his studies of how insects use chemicals. He claimed that each species of insect relies on 100 or more chemicals during its lifetime.
His most famous discovery was the weaponry of the bombardier beetle. This insect was found to have two separate internal reservoirs: one for hydrogen peroxide and the other for hydroquinone. When threatened, this beetle sprays both together where they combine with an enzyme in an exothermic reaction to produce a burning spray of 210 degrees.
Using a similar line of defense, the wood ant produces formic acid from its rear end when its mound is threatened. The acid is so acrid that one can actually smell it!
The Discovery of Pheromones
Chemicals can be used in ways that are imperceptible to humans unless carefully studied in the lab; however, these same chemicals are used by insects for communication.
Whereas humans use eyes, ears, and voice, insects use these "messenger chemicals" called pheromones. They are involved in mating, finding food, detecting enemies, protecting offspring, and escaping predators. The queen bee actually uses pheromones to direct hive activities to her worker bees.
The first of these attractant chemicals was discovered in 1936 by Adolf Butenandt and a team of German scientists. They worked for 20 years to isolate enough fluid from the abdominal glands of female silk moths to conclusively analyze its chemical make-up. The substance was named "bombykol" after the species of moth from which it was derived.
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They observed that a tiny amount would make a male respond with a "flutter dance." In 1959, Peter Karlson and Martin Luscher named these chemical attractants pheromones from the Greek meaning "I carry stimulant."
It was stated by Lewis Thomas in his book, The Lives of a Cell, "if a female were to release all of her pheromone at once, she could theoretically attract a trillion males in an instant." Now that's some powerful perfume!
Unlike sight or sound, pheromones last longer and extend further distances, permeating in many directions at once where they cast a larger net. A male silk moth has been found to travel over 30 miles to mate!
Sex pheromones can also be used as a mating deterrent by overwhelming the male with too much scent. In areas of heavy cotton production where the beet armyworms are a serious problem, farmers often spray their fields with a female sex attractant chemical. The poor male is so confused that he is unable to single out a mate. The result is a pretty effective birth control.
Honey bees communicate with members of the hive through the use of pheromones too. There are many types, each specific in its message. They send information about the health of the queen and the hive in general. The queen can relay messages regarding mating behavior, egg-laying, and swarming to reduce colony size.
Bees relay food sources to other hive members through a waggle dance. The movements, in relation to the position of the sun, relay both distance and exact direction. This information, however, is not enough. The bees must also carry the scent of the flowers for the actual pollination source to be found. Communication within a bee's social network is highly complex.
Examples of Chemical Defense
Bola spiders can produce a pheromone that mimics that of a female moth so that a male in search of a mate will find himself in a web instead.
There is the female rattlebox moth, Utetheisa ornatrix, which feeds on plants containing poisonous alkaloids during her larval stage. She retains her poison through metamorphosis into adulthood. During mating, the male passes on more alkaloid toxin which she, in turn, passes to her eggs. This chemical transfer protects the eggs from predators and makes the adult moth distasteful to spiders. Rare is the spider who will free a moth from his web, but this clever moth gets a ticket to freedom. Now that's brilliant strategy!
One species of female firefly that doesn't produce toxic chemicals of her own has learned to fake a mating signal to lure an unsuspecting male. She then kills and eats him in an effort to steal his immunity. How shrewd!
Ladybugs, like Monarch butterflies, use foul taste as a defense by producing a chemical to make it distasteful to birds. Aquatic beetles produce one that makes fish spit it out.
Pheromones are also used to protect eggs in order to perpetuate a species. An example is the aforementioned rattlebox moth and her foul tasting eggs. Another twist comes from the male mealworm beetle who will mate with a female then mark her with a pheromone that makes her unattractive to any other potential mate.
Through clever design, the earwig will always be guaranteed an accurate one-two punch because its defensive spray comes from between the two rear pinchers. That's a defensive double whammy!
In an interesting self-sacrificing maneuver, the Asian formicine ant, Colobopsis saundersi, will blow itself up to disperse its sticky acid remains and entrap threatening enemies in the residue to protect the colony.
Nature's Pest Control
Parasitic wasps have evolved to recognize and follow the sex attractant of host insects. Once they locate them, they lay eggs inside the host or parasitize and eat it. They have become one of the best biological controls we have today against aphids, scales, caterpillars, and whiteflies.
Pheromone traps are widely used by the USDA to trap insects for study and population assessment. We also use them to attract ladybugs, lure yellowjackets and fruit flies, and to catch Indian meal moths and citrus leafminers onto sticky strips.
Observe and Learn
I am always in awe of the many fine examples of nature's ingenuity and encourage taking the time to observe. This summer you might see a wasp hovering around your tomato plants. Don't panic and run for the bug spray! Instead, watch as it carefully positions itself to lay its eggs into the body of that ugly green hornworm. You are witnessing a biologic predator in action just as nature designed it.
Agosta, William C. (1992) Chemical Communication: The Language of Pheromones
Eisner, T, Eisner, M, & Siegler, M, (2005) Secret Weapons: Defenses of Insects, Spiders, Scorpions, and Other Many-Legged Creatures. Harvard University Press.
http://ipm.ucanr.edu- parasitic wasps
http://www.sciencedirect.com/science/article/pii/S096098221000240X- honeybee communication
https://www.si.edu/Encyclopedia_SI/nmnh/buginfo/pheromones.htm- beetworm mating
https://en.wikipedia.org/wiki/Utetheisa_ornatrix- rattle moth behavior
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2011 Catherine Tally
Catherine Tally (author) from Los Angeles on January 21, 2012:
Cardozo7, Insect behavior fascinates me. Thanks for stopping by and reading. I appreciate your comment!
Cardozo7 from Portugal on January 20, 2012:
Insightful hub. Lots of knowledge in here. Thanks for the info
Catherine Tally (author) from Los Angeles on May 25, 2011:
I appreciate the nice comment. Thanks for reading!
mabmiles on May 25, 2011:
Very wonderful hub, Thanks for sharing this.
Catherine Tally (author) from Los Angeles on April 22, 2011:
I'm so glad that my hub peaked your interest in bugs. Thank you Vitamin Monkey for following me :>)
Vitamin Monkey from San Francisco, CA on April 22, 2011:
quite fascinating! never new so much about insects!
Catherine Tally (author) from Los Angeles on April 20, 2011:
Thank you,Isabel! Design in nature is really complex and amazing.
isabelprontes on April 20, 2011:
A very interesting read!
Catherine Tally (author) from Los Angeles on April 13, 2011:
You're welcome, Alicia! Thanks for reading. I'm really glad you enjoyed my hub as much as I enjoyed writing it :>)
Linda Crampton from British Columbia, Canada on April 13, 2011:
Thank you for a fascinating hub with excellent information and a great video!
Catherine Tally (author) from Los Angeles on April 13, 2011:
I am so glad you enjoyed this. When I read Thomas Eisner's obituary, I felt compelled to write about this topic that has always interested me. Thanks for your comments :>)
I appreciate your nice comments and am glad you found the information interesting. Thanks for reading.
Teylina on April 13, 2011:
Really, really good info. Thank you.
Teylina on April 13, 2011:
Really, really good. Thank you!
Harlan Colt from the Rocky Mountains on April 13, 2011:
This is excellent. I love this kind of study. Very nice job and a decent read! Excellent!