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Sunday September 2, 2012


Mr Pest Control


There is a debate going on between myself and another pest control company here in the Southwest. He claims and tells his customers that our bark scorpions come up the house drains and this is the reason they find them in sinks and tubs. My belief is they do not and cannot come up the drains from the sewers and the reason people find them in sinks is that they crawl in or fall into them. Please settle this issue!

susan, NV

Mr Pest Control


I really do feel uncomfortable getting in the middle of disagreements, so I'll try to be diplomatic with my response. Let's examine one thing first, based on my basic knowledge of plumbing. ALL sinks and drains in a structure should have, if properly constructed, a "P" trap below the drain. This is a u-shaped curve in the pipe that retains water, and the purposes of this P-trap are to keep out odors from the sewer and to prevent insects from coming up that pipe from the sewer. Now, I never say never when it comes to bugs, and I used to feel confident stating that even American Roaches should not be able to swim past that water barrier in the P-trap, and therefore "should" not be able to enter homes directly from the sewer. However, I have been corrected twice now by technicians who claim they have personally watched American roaches go down into a drain and continue walking right down into that water barrier. In one case the roach returned within about 30 seconds and in the other it never reappeared, suggesting that it just continued down through the water and on toward the sewer. 

So, what is the chance that a scorpion will be living down in a sealed, enclosed sewer or perhaps in a septic tank in the first place? I think this would be very out of character for scorpions, which definitely prefer a warmer, drier environment, particularly in your area in the southwest deserts. It is impossible for them to be in a sewer? Well, I wouldn't go quite that far, but it just seems that it is much more likely that they are living above ground and finding ways into the structure that are more in keeping with their life style. It also would seem out of character for a scorpion to willingly take the plunge and move into a water barrier like you have in the plumbing. 

What I believe definitely CAN happen is for scorpions and many other insects to fall into a slick-sided sink or tub of porcelain and not be able to climb back out again. This is why we find silverfish and so many other bugs in tubs and sinks. They fell in, perhaps detecting moisture there that they were seeking or perhaps just being clumsy. I think that given the two choices - up from below or down from above - the far more likely reason the scorpion is there is because it was wandering around in the home and just fell in. 

Bark scorpions in the genus Centruroides are excellent climbers, and their name is given due to their tendency to climb trees and shrubs outside. If branches then touch the structure this enables them to get onto the structure, perhaps the roof, and from there easily find some gaps where they can enter the attic or into wall voids. The bark scorpions, according to some resources, can squeeze themselves down so flat that they can move through a gap only 1/16th inch wide. Clearly this is hardly anything, and it makes your job of providing exclusion that much more of a challenge. But, permanent exclusion for the structure and habitat modification for the landscape are two of the keys for managing scorpions long term. 

In this case I think I need to side with you and go with the more logical approach that the scorpions have found their way inside via holes and gaps around the exterior of the structure, and then in their wanderings have fallen into these places where they cannot manage to get back out of. 

Mr. Pest Control

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