Aquatic Field Trip
In this lab you will observe and collect insects found in aquatic habitats.
The main objectives of this lab are to help you:
- learn where to look for insects and how to collect them safely
- distinguish the eight common orders of aquatic insects based on physical appearance
You will need the following materials for this lab:
- Wide-mouth collecting jars or plastic boxes
- Insect pins
- Paper “points”
- Permanent ink pen – fine point
- Date/locality labels
- 4-dram glass vials
- 70% ethyl alcohol
- Flat bottom white pan
- Kitchen sieve or dip net
- Kick seine or window screen
- Rubber boot or hip waders
For your third field trip and insect collecting expedition, visit a small lake or farm pond as well as a creek or small stream with clean running water. If you live near a large city, it may be difficult to find unpolluted bodies of water that harbor good insect diversity. You may be able to contact biology teachers or environmental science teachers at local high schools or community colleges for recommendations on good sampling sites. Aquatic insects, especially those in the orders Ephemeroptera, Plecoptera, and Trichoptera, are often used as “biological indicators” of good water quality.
Your aquatic field trip is a good opportunity to collect insects in the following ecological categories:
- Aquatic nymph
- Aquatic adult
- Vertebrate parasite
- Case maker
- Watch the Aquatic Field Trip video to get a preview of what these insects look like and how to collect them.
- Tour the Picture Gallery of Aquatic Insects to see examples of pond and stream insects.
- There are only eight insect orders commonly collected from aquatic habitats. Most of these are easy to recognize based on the following characters:
- Odonata – look for the labial mask used to catch prey
- Ephemeroptera – look for a pair of leaf-like gills on the sides of each abdominal segment
- Plecoptera – look for hair-like gills at the base of each leg.
- Hemiptera – look for piercing-sucking mouthparts
- Neuroptera – look for two claws on each abdominal proleg
- Trichoptera – look for a single claw on each abdominal proleg
- Coleoptera – look for a well-developed head capsule and no abdominal prolegs
- Diptera – look for head capsule reduced or absent, single proleg behind the head, or fleshy gills at the back of the abdomen
Remember, only hemimetabolous insects qualify as aquatic nymphs!
Use a dip net or kitchen strainer to collect insects from the shallow margins of a lake or pond. Focus your effort around the base of emergent vegetation (reeds, cattails, etc.) and in the muddy detritus that accumulates on the bottom of the pond. Use your net or strainer as a scoop and transfer your catch into a white pan containing clear water. Sift through the sample slowly and you will see the insects as they swim out into the clear water. Preserve your specimens by putting them directly into 70% alcohol.
Find a section of your stream where the water riffles through small rocks. Put your screen, kick seine, or dip net just downstream from these rocks as you jostle them with your hand or foot. Let the stream water wash the loosened sediments into your seine, transfer this sample to a shallow white pan containing clear water, and look for aquatic insects that were displaced by your disturbance. Look carefully on the undersides of the rocks for clinging insects like mayfly naiads, water pennies (beetle larvae), and caddisfly cases. Preserve your specimens by putting them directly into 70% alcohol.
3. Preserve and Pin
Be sure to put a date/locality label on every specimen, using the format described in the collection instructions. Keep good notes to help you remember which insects fulfill ecological categories. You will add Ecology labels later after you have identified the specimen.