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  • Writer's pictureChelle Hartzer

Sweating the Small Stuff (AKA: No sweat!)

I was outside this past weekend getting some yard work done. It was supposed to be a bit cooler than it had been for the past few months. It wasn’t. By the time I was done, I was literally drenched in sweat. Really, you could wring out all my clothes and fill a small bucket with what I had sweated out. This morning I heard this on NPR. So we have to talk about pests and water loss.

Let’s start with something that doesn’t sweat: rodents. Humans sweat to keep us cool (though it certainly didn’t feel that way this weekend when I was working). Rodents are able to thermoregulate by decreasing or increasing their metabolism or avoidance. So instead of being out in the sun working their little butts off weeding, they are smart and stop moving so much and head for the shade.

It’s commonly accepted that rats need a daily source of water while mice can survive off the moisture in their food if they need to. There has been quite a bit of research on this because laboratory rodents need to be kept in humane conditions. Apparently, rats can go about two weeks without water before succumbing to dehydration assuming they have food. Mice “adapt to chronic water restriction of as much as 50% of the ad libitum daily ration that is imposed over an interval of as long as 8 d.” I needed about two gallons of water when I was finished weeding.

Stored product pests like flour beetles, Indian meal moths, warehouse beetles, and more survive in very dry environments. Your box of breakfast cereal or bag of flour has very little water content but these insects are able to survive in these habitats. Through a complicated process of eating starchy foods, breaking down starch into sugar and water, they are able to essentially extract water from their foods. There is a really good explanation of that here. Additionally, the beetles are covered in a waxy layer over their exoskeleton which helps hold moisture in. They don’t sweat like I do.

The larvae are a bit more susceptible to water loss and need a minimum level of humidity to complete their development. For flour beetles, the eggs can’t survive below 10% RH, and larvae didn’t make it to adult stage at below 30%. There is one more way that some of these insects are able to avoid water loss and other unfavorable environmental conditions. Some Dermestid beetles can actually reverse their growth and go into a diapause until conditions are better. The Khapra beetle can do this for 8 years! (I wish I could sleep through the entire summer.)

Other pest species are very reliant on moist conditions and will “follow” moisture. Springtails and psocids (AKA booklice) are great examples of this. They are very soft bodied and live in soil and leaf litter. When conditions start to dry out in one place, they start moving to areas of higher moisture. This can lead them below buildings and up through expansion joints and other tiny cracks. Having dehumidifiers and fans to move the air can significantly reduce their numbers.

Another way insects may lose water is through reflexive bleeding. Lady beetles are a pest in late autumn when they enter structures in high numbers. When they are disturbed, they can exude a fluid through their leg joints. This is to deter predators. It makes sense if you are losing your body fluids, there is going to be a drawback. In this case, studies have shown that this will weaken their immune system leaving them more susceptible to pathogens.

There are plenty more pest species that can survive with very little water, can resist water loss, or are able to seek out the water they need. Thinking about moisture and water sources as part of a comprehensive pest control program is important to successfully manage them. And we can help you with that, click here now to schedule a complimentary meeting. I promise to shower off the sweat before our meeting!

Lagniappe – “Juicing” dead spiders with water turns them into a claw machine:

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