Field Stories: Collecting Giant Water Bug Eggs for Study

I’ve found that there are two types of field biologists.  There are those that have cushy, fabulous research positions that everyone is jealous of.  The husband of one of my good friends works with squirrels in Arizona.  He spends a good part of the summer on top of a gorgeous mountain hiking through the forest studying adorable little frolicking squirrels.  If you’re an outdoorsy person, this job is one little slice of heaven.  His wife, on the other hand, is my coworker for one of my jobs.  We are on the other end of the spectrum – field biologists who tell people what we do and watch them cringe in horror or utter disgust.  We’re the ones that get questions like, “Ugh!  Why would anyone want to do that?”

In order to stay sane, I find that biologists like us revel in the intensity or relative digustingness of our work.  We share stories and try to one-up each other so that we can convince people that we have the worst field assignments ever.  We are martyrs to science, gosh darn it!  Many of our conversations involve the words, “You think that’s bad?  Let me tell you about MY field site!”  So before I get to my post on why brooding is bad for male water bugs, allow me to tell you about my lovely field site and my experiences there.

This is the pond at my field site:

My field site!

My field site!

Isn’t it lovely?  Let me tell you about this pond.  This is what’s considered a “cattle tank” in Arizona.  If you’re not from AZ, you probably think a cattle tank is a round metal container that is filled with water from which cattle can drink.  I certainly did before I moved here.  No, in Arizona, cattle tanks are little man-made ponds.  Farmers basically pile up dirt at the low point of a natural depression to create a pond that fills with water during rains.  My particular pond collects an amazing amount of overland flow.  It can go from almost empty to completely overflowing in a single rain event, so it’s a great example of a cattle tank.

All that green stuff on top is algae.  Because it is fed by overland flow, the water brings a lot of organic materials, soil, and nutrients with it as it flows into the pond.  When the pond first fills up, the water is opaque brown from all the dirt.  But when you have a body of water with a whole lot of nutrients in it, you get algae.  LOTS of algae.  If you get into my pond, you come out green!

And then there’s the livestock.  This pond is used by cows and horses.  They don’t seem to have any problems with using the pond as both their drinking water and their toilet.  If you get into the water, you have to watch for floating road apples and cow patties and you smell like urine for the rest of the day, sometimes even after you shower.  It’s lovely.  And all that stuff the livestock dump in the pond contributes to the algae growth, making it even more green!

Finally, there is the mud.  Between the cow and horse “contributions,” the dirt flowing into the pond with the rainwater, the algae that dies and falls to the bottom, and the decaying plants and wood that fall in, the mud in the bottom of the pond is sticky, stinky, and deep.  Every time you take a step, you sink into the mud, almost up to your knees.  It’s hard work moving through this sort of mud.

Did I mention the tempature of this pond?  The water is really warm, a lot warmer than you would expect it to be from the air temperature.  All the cows and horses and other lovely things that are in the water promote the growth of bacteria.  The water is so hot in part due to the fermentation and other bacterial processes that are occurring in the water.  All those chemical reactions produce heat, so the water becomes warmer than it would be if it were clean.

There’s nothing  quite like getting into hot, stinky, opaque green-brown water and sinking into putrid mud, let me tell you.  I dread getting into my pond.  If I have to meet with people after I go to my field site, I have to warn them that I’m going to my field site in case I show up covered in mud and scented with urine.  I complain about it to my collagues and definitely drag out the list of offenses my field site provides in those one-upping conversations – and often win!  So, why do I do it?  This is why:

Lethocerus medius

Lethocerus medius brooding eggs

My pond is a fantastic place to collect Lethocerus medius eggs!  If you recall from my post on giant water bug parents, Lethocerus are emergent brooders and lay their eggs on emergent vegetation.  This means the bugs require emergent vegetation if they want to reproduce, and Lethocerus medius is no exception.  It is worth putting up with the nasty conditions of my pond for this reason: there are tons of Lethocerus medius, but almost no emergent vegetation!  This means there are lots and lots of bugs looking for places to lay eggs, but almost nowhere to lay them. This creates great conditions if you need to collect eggs from a Lethocerus species, which are notoriously hard to breed in the lab.  All you need to do to get eggs is provide artificial emergent vegetation.

We use sticks clipped from desert broom bushes, strip the leaves off, and then I wade into the pond and stick them into the mud:

Artificial emergent vegetation

Artificial emergent vegetation

Once you’ve put the sticks in, the bugs are more than happy to use them for mating.  During the right time of the year (monsoon season for this species and location), if you come back the next day you are likely to find clutches of eggs attached to the sticks.  I pull the sticks out and bring them back to the lab with me so I can do experiments with the eggs.  Then we go back the next day to get some more.

In spite of the general ick factor of my field site, it is completely worth it to use this pond.  There are very few ponds that have this little emergent vegetation and collecting eggs anywhere else would be a whole lot harder to do.  It is also definitely easier than setting up a brooding operation in the lab.  It might not be glamorous and I’m waiting for the day I fall in head first, but the results of my experiments are exciting enough to keep me going back.  Hooray for the thrill of scientific discovery!


Text and images copyright © 2009


2 thoughts on “Field Stories: Collecting Giant Water Bug Eggs for Study

    • I really didn’t ever tell you about my adventures at the pond? Guess we always talked about our dogs instead. :) Glad you’re enjoying the aquatics! I can say the same about your bees!

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