Analysis of the entomological accuracy of the article : Survivors; 350 Million years later, Cockroaches are still going strong. Dr Houseman Bio3323

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1 Analysis of the entomological accuracy of the article : Survivors; 350 Million years later, Cockroaches are still going strong Dr Houseman Bio3323 Department of Biology University of Ottawa January 28 th 2005

2 Introduction On November 10 th, Susan Okie from The Washington Post wrote an article for the general population about cockroaches. It explains how the cockroach with is fabulous adaptive expertise survived the dinosaurs, the ice ages and other obstacle that larger and smarter animals were incapable of surviving. It explains how the cockroaches lives and survives in very details. Although, the main goal of the author is clearly to make us like them even less than humans already do. The scientific readings used to compare the bare facts with those emitted in the article where Cockroach by Marion Copeland, Insecticide resistance mechanisms in the German Cockroach, Blatella germanica by Siegfried D. Blair and Jeffrey G. Scott and Aggregation agents in German cockroach: examination of efficacy The article is written for the general population; so while it has a lot of details, they are not relevant and not explained in depth. Emphasis in this article is placed more on the disturbing habits that cockroaches had to gain to survive so long. Although the scientific information is genuinely accurate, it only skimmed the surface about the resistance to insecticide for cockroaches, or about the scent emitted by cockroaches that is so strong. Knowing how they adapt to insecticide and gain resistance would help get rid of a cockroach infestation (which are not uncommon) and what not to use because cockroaches are known to have adapted to it. Helping our environment and yours. Also, knowing about that scent might help you realize the pheromones being the mode of communication it is, we might use it to get rid of the cockroaches with pheromone traps.

3 Scents emitted by cockroaches Cockroaches emit a very peculiar and distinct scent called pheromones. Pheromones are used to convey information from an individual to another (Bell, 1981). There are 3 types of pheromones induced by cockroaches: (1) sex pheromones: extracted from the cuticle of females that induces wing-raising in males; (2) dispersal pheromones found in saliva of nymph and adult. The high dispersion activity was found in a protein in the saliva. (3) Aggregation pheromones that are still a dark subject and contradictory (Scherkenbeck et al, 1999). The aggregation pheromone and reduced locomotion activity is found in feces which was proven before by using traps with feces and without for example. The aggregation pheromone consists of a multi-component mixture separated in volatile, attractive principle and non-volatile, arresting principle (Scherkenbeck et al, 1999). The sex pheromones clearly play a role in the hierarchy status in the cockroach colony. But here, the pheromones emitted by more passive males are preferred than the scent emitted by dominant aggressive males (Bell, 1981). Males compete for females favours in dominance rituals. As soon as you put two males together, one of the males will chase after the other, jumping on him and charging with his head structure like a ram (Discover, 1998). Something might dictate the outcome from the start. It is sex pheromones that determine which male will dominate and which male will run. They verified that hypothesis by putting patches of the 3 ingredients of sex pheromones separately and in combination. One of the ingredients had no effects but when you put the two others alone or in combinations, the male suddenly begins to fight, butt and kick other males. But why create a pheromone that is less approved by females. The males with the three components are preferred to the other super aggressive males. After all, the female risks being injured by those dominant males What happens is that the dominant males use their 2 components of the pheromones faster and use them much faster so when the dominant males have ran out of

4 pheromones than the passive males become dominant and can at their turn win the females. Patience is a virtue even in the cockroach world ( Moore, Discover, 1998). Resistance to different insecticide One of the reason for the evolutionary success of cockroaches is due to their quick ability to adapt to different circumstances. Cockroaches are considered like serious pests and even more since they have developed different resistance to insecticide used against them (Copeland, 2003). Different resistance mechanisms are used to get accustomed to the insecticides like increased metabolic detoxification, decreased penetration and target site insensitivity. Over the years the German cockroach has acquired resistance to the insecticides of different groups: the organochlorines, the organophosphate, the cabamates and the pyrethroid ( Siegfried and Scott, 1992). The acquisition of resistance started with the DDT in the 1950s and propagated quickly so that all cockroaches are now resistant to DDT. Because of their ability, the German cockroach is now resistant at different degrees spread out sporadically in the US to different insecticide like diazinon, fenthion, malthion, and propoxir ( Siegfried and Scott, 1992). Target site insensitivity was observed by comparing resistance strain with sensitive strain to malthion. It resulted with increase in the rate of inhibition of acetylcholine esterase in the susceptible strain. They then tried the same experiment with organophosphate and carbamate and did not distinguish any significant difference in the inhibition rate of the acetylcholine esterase. The controversial results obtained are explained by the minor role of target site insensitivity in the cockroach. It is used more in other insects, but this mechanism of acquisition is very rarely used among cockroaches. Another type of target site insensitivity is by nerve insensitivity which is the mechanism acquired by German cockroaches to be resistant to cyclodiene insecticides ( Siegfried and Scott, 1992).

5 The penetration barrier is linked to a lot of insecticide resistance but most of the time it is enhanced with other mechanisms; so that it is hard to tell up to what point is the real contribution of the barrier resistance. The barrier resistance is tested by comparing the resistance to different insecticides injected vs topically applied. For DDT the resistance was 20-fold higher then the one injected and 4-fold higher for diazinon. Finally, the metabolic detoxification in German cockroaches as been established for a few compounds only but the information available on this mechanism leads us to think that it is involved in resistance to other insecticides. The experiments done to verify this kind of resistance are mostly synergism studies where the cockroaches observed are strain of multiresistant to insecticides. The multiresistant strain saw their resistance level suppressed because of the combined metabolism (Siegfried and Scott, 1992). Conclusion While the article is written for a very broad audience, the details concerning the cockroach in general are very uninteresting. It is a long list of facts that are pretty irrelevant except for the fact that it makes us hate the cockroach even more because it has lived longer than us, humans. Although it surfaces some interest points, I think it would have been better to go in more depth of certain facts like the pheromones which is an interesting phenomenon that is more and more adapted to the humans. Also the resistance to insecticides would have been a very important to go further into the subject to learn about the environment problem that concerns us all. It is unfortunate that the author of this article did not put in perspective the amazing abilities that cockroaches have obtained during the millions of years they have been on this earth without changing significantly their physical traits and adaptations. Instead, the cockroach will always stay to the untrained eye the human world s biggest pest

6 References Okie, S., Survivors; 350 Million Years Later, Cockroaches Are Still Going Strong, Washington Post, November 10 th 1999, page H.01, document URL: Discover, February 1998 Copeland, M., Cockroach, Reaktion books ltd, London, England, 2003 Bell, W.J., The laboratory cockroach; Experiments in cockroach anatomy, physiology and behaviour, University of Kansas, Lawrence, Kansas, 1981 Siegfried, B.D., Scott, J.G., Insecticide resistance mechanisms in the German cockroach, Blattella germinica, Molecular mechanisms of insecticide resistance, February 18 th 1992, American chemical society, Washington Scherkenbeck and al, Aggregation Agents in German Cockroach Blattella germanica: Examination of Efficacy, Journal of Chemical Ecology, Volume 25, Issue 5, May 1999 Bayer AG, Central Research, Leverkusen, Germany, Zoological Institute, University of Cologne, Weyertal 119, D Köln, Germany, document URL: , Journal of Chemical Ecology (Vol: 25, Issue: 5) pp

insect pests. Cockroach control has been extensive with many available types of traps, chemical

INTRODUCTION When it comes to dealing with irritating insects, cockroaches are among the most loathed insect pests. Cockroach control has been extensive with many available types of traps, chemical control