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On Six Legs by Tom Turpin - cockroaches

To most people, the word cockroach is sure to elicit some expression of disdain, if not outright revulsion. Indeed, cockroaches are a group of insects that are almost universally viewed as some of the most disgusting creatures on the surface of the earth.

It is not real easy to explain why cockroaches have managed to become one of the most reviled of all the insects. It is fairly obvious why we humans don't like those insects, such as the bees and wasps that sting. Insects such as mosquitoes that suck blood and can transmit disease organisms certainly have earned the wrath we bestow upon them. And those insects that eat our plants or our possessions, well grumbling about them seems justified.

But cockroaches don't really do much to harm us. For sure, some people, especially children, develop an allergic reaction to the chemicals produced by cockroaches, and this is a health issue.

The real reason we don't like cockroaches is that they are cockroaches! Yes, it seems that the very word cockroach is the basis of our hate, with or without any real association with the insect.

Years ago one of my students did a study of people's reaction to insects. She showed people 10 pictures of unnamed insects and asked them to rank the insects from 1 (most willing to hold) to 10 (least willing to hold). One of the insects was a cockroach.

Based on insect pictures, the average willingness-to-hold ranking for a cockroach was fifth on the list. Only four insects, including a butterfly and a ladybug, ranked above the cockroach in this survey.

When the participants in the study were asked to repeat their ranking using only the common names of the insects, such as butterfly, ladybug or cockroach, the relative ranking for the cockroach changed dramatically. The cockroach dropped from No. 5 to No. 9, next to last of the insects on the list. Only an obvious stinging insect, a wasp, was ranked lower by name.

Based on these results, it appears that just the word cockroach is reason enough for people to not want to hold such an insect. The results suggest that some people did not correctly identify a cockroach from a picture and not knowing the name for the insect would have been willing to hold it relative to other insects shown.

In another example, when people are given the opportunity to touch a large species of cockroach, almost three times as many people will do so if they are told the insect is a beetle than if they are told it is a cockroach. Again, it is the name cockroach that makes all of the difference!








But in spite of our disdain for cockroaches, one cockroach species has become a favorite insect for classroom colonies, insect zoo displays and exotic pet. This species is Gromphadorhina portentosa, known by many people as the Madagascar hissing cockroach.

Hissing cockroaches have risen above the other 3,000 or so species of cockroaches known worldwide to at least be tolerated by a few humans. There are probably several reasons for this. The hissing cockroach is the largest species of cockroach in the world. It is a wingless species. It is easy to keep confined to a cage. It doesn't reproduce as rapidly as many other species of roaches. Colonies of hissing roaches don't produce the odor that many other cockroach colonies do. And you can handle these roaches without fear of them getting away and infesting the premises.

Madagascar hissing roaches are useful in the classroom to study the biology of arthropods. The insects can be used to observe the process of invertebrate growth, including metamorphosis and the shedding of the exoskeleton. This process frequently results in students finding a white cockroach in the colony. This white individual has just emerged from its old exoskeleton and has not yet had time for the new exoskeleton to expand, harden and color.

The fact that these cockroaches make a hissing sound also is intriguing to some people. Other insects produce sound but none do so by expelling air out of breathing orifices, which are called spiracles. The sound is used to attract a mate, establish territory or scare predators – think snake here.

At Purdue University, we harness these big cockroaches and have them pull tractors in a cockroach version of a tractor pull. I say if cockroaches are that size you might as well put them to work!