Collecting Insects: A Net for Collecting Aquatic Insects

It’s been too long since I last posted a tutorial for my Insect Collections series, so today I’m going to share my best secret for collecting aquatic insects.  A lot of people overlook aquatic insects when they work on their collections.  It’s a shame really – there are some fantastic insects in water if you take a few minutes to look!  I think part of the problem is that most people think you need to have fancy nets that cost $60+ or other special, expensive equipment to collect in water.  This couldn’t be further from the truth!  Today I’m going to show you how to make and use a reasonably sized, easy-to-carry aquatic net for collecting insects in water, one that my advisor recommended to me when I started grad school.  Are you ready for this complicated design?  Breathe in through your nose and out through your mouth to prepare your mind for the complicated steps this tutorial is going to involve.  Ready?  Then gather the things you need:

Essential Equipment

soup strainer

Essential equipment

  • one sturdy all metal kitchen strainer, preferably stainless steel.  (A solid frame around the basket is essential, so make sure that part isn’t going to collapse or separate from the handle if you put a little pressure on it.)

Whew!  Are you tired yet?  And if you want to be REALLY fancy, then you’ll want these things as well:

Optional Equipment

strainer extras

Optional equipment

  • metal rod, stick, dowel, etc (my metal rod came from Bioquip and cost around $8, but anything long and roundish that’s reasonably comfy to hold will do.  Avoid things that might give you splinters!)
  • duct tape (any project worth its salt involves duct tape, so you know this is gonna be good!) or waterproof tape

Okay, you’ve gathered your equipment.  Now let’s put the net together (here comes the complicated step):


soup strainer

Completed net. (Note: the duct tape on the handle is there to identify this as my strainer when I'm out with my students on field trips. It has no other function.)

Congratulations!  You now have a really great little net for catching aquatic insects!

I’ll admit that people scoff at my soup strainers and I get laughed at when I strap several of them onto my fishing vest.  Granted, I do look like some sort of deranged Kitchen Rambo stomping around in streams and ponds.  However, regardless of how dorky you look as you strain a pond or stream, soup strainers make fantastic aquatic insect nets!  For one thing, they’re cheap.  Look for sales and you can frequently get all metal strainers for less than $10 at stores like Target, Wal-Mart, and Ross.  Cheap is good.  If one breaks, simply chuck it in the recycling bin and start using a new one.  If you lose it, who cares?  The metal mesh also doesn’t get ripped the way aquatic nets do, so they’re super durable.  Soup strainers are lightweight, so you can carry several with ease.  I have a carabiner hooked onto my fishing vest that I loop through a couple of strainers when I’m out in the field.  And, they’re easy to use.  Trust me – it’s hard to beat a soup strainer for collecting aquatic insects.  I have a fancy aquatic D-net and I hardly ever use it.  Instead, I use my soup strainers.

There are 2 downsides to using soup strainers though.  One is that the mesh size is large, so sometimes it is best to use the more expensive “official” aquatic insect net, especially if it is important to know the number or diversity of insects you pull out of the water.  The other downside to soup strainers is that they’re short, so you have to get your hands wet to use them.  That’s not so bad if you live in AZ and the water rarely gets down below 40 degrees.  I lived in Colorado for a long time though, so I know there are places and times of the year when you really don’t want to stick your hands in the water.  That’s where the optional equipment comes in!  Here comes another complicated step.  Cut off a 12-15  inch long piece of duct tape and tape the handle of your strainer to your longish, roundish, pole-like object:

strainer with extension

Strainer with extension

Tada!  Now you’ve got yourself a nice long handle that keeps you well away from the water and allows you to collect in deeper water without getting wet.  You’ll need to replace the tape occasionally, but you’ll get a lot of use out of your MacGyver’ed soup strainer before you do.  If you spring for a more expensive roll of waterproof tape, it will last a lot longer.

Using your strainer is easy!  In a stream, hold your strainer in the water so that it is downstream of the area you wish to sample.  Stir the substrate up, either with your other hand, your foot, or with the front edge of the strainer.  Let the loose material flow into the strainer bowl, pull the strainer out of the water, quickly sift through the material in your net, and pluck the insects out!  (I recommend using feather forceps for handling aquatics as a lot of them are very soft-bodied and you don’t want to crush them.)  Dump whatever’s left back in the stream.  You’ll use a similar substrate-stirring technique in ponds, but you’ll have to sweep the net through the stuff you stir up because there’s no flow.  If you get a bunch of muck in your strainer, simply hold your strainer at the surface, half in the water and half above the water, and swish it gently back and forth.  The silt and other small debris will flow out of the strainer and leave the bigger things behind.

I know, I know.  It sounds completely stupid.  But it works!  I’ve handed soup strainers to well over 100 people in the last few years and I’ve won a lot of converts.  It’s amazing what you can collect with them.  Considering the price, the ease of transport, and the ease of use, you can’t go wrong.  I use mine all the time!

Me collecting in Florida Canyon

Me collecting in Florida Canyon with my trusty soup strainer!

Happy collecting!


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Unless otherwise stated, all text, images, and video are copyright © 2010

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