Blue-winged Olives
Baetis
Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
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This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
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Identification: Key to Orders of Adult Aquatic Insects, Couplet 2
Identification: Key to Orders of Adult Aquatic Insects, Couplet 2
Error: Tried to access a key that isn't live.
Adapted from Merritt R.W., Cummins, K.W., and Berg, M.B. (2019)
| Option 1 | Option 2 |
|---|---|
| Mouthparts made for chewing, with mandibles visible | Mouthparts made for sucking, with mandible concealed and a jointed beak (rostrum) visible 
|
| Remaining orders: Coleoptera and Orthoptera | |
4 Example Specimens
You wouldn't know to look at it, but this is an aquatic beetle and it's in water in the photographs.
This is an iridescent green terrestrial beetle. They're common in northern Wisconsin's forests during the middle of summer, and I found them on the water's surface more than any other terrestrial insect. I saw the trout take a few and caught some trout on an imitation.
This is a water beetle. It is the hardest object in the world to pick up with tweezers. The second hardest is Mount Everest.
| 5 Example Specimens
I'm glad I finally got one of these Belostoma water bugs under my good camera. I had been hoping to get one in my kick-net samples for a while with no luck, but I ended up finding this one drifting midstream just below the surface while I fished. I have frequently seen water scorpions do that, too, and I'm beginning to suspect that is a common situation travel for these large Hemiptera bugs, and perhaps the way trout are used to seeing them.
I found this cicada and several like it in the grass near my car as I put my waders on. Some of them were singing in the trees above the river, too, but I did not see any fall into the water.
Here's a big water scorpion (no relation to actual scorpions). These guys are just about the most sinister-looking creatures you could find, and what's especially creepy is that they can come up out of the water and fly around, as I learned when one left my aquarium and buzzed my head while I was peeking into the microscope at a mayfly nymph.
Every picture of this specimen was taken with my old camera through a microscope.
|
| Go to Couplet 3 | Hemiptera |
Adapted from Merritt R.W., Cummins, K.W., and Berg, M.B. (2019)
The current couplet is highlighted with darker colors and a icon, and couplets leading to this point have a icon.
Leads to Couplet 2:
- Forewings leathery (semiopaque) or hard, at least in the basal half
Couplet 2
Leads to Couplet 4:
- Wings entirely membraneous, usually transparent between veins, but may be variously colored, darkened, or covered with hairs or scales
Couplet 4
Leads to Orthoptera:
- Forewings leathery, with distinct veins
- Femora of hind legs greatly enlarged, suited for jumping
Leads to Coleoptera:
- Forewings hard (called elytra), with veins indistinct; hindwings membraneous but often concealed
- Hind legs suited for walking or swimming
Leads to Couplet 5:
- One pair of wings
Couplet 5
Leads to Couplet 6:
- Two pairs of wings, although hindwings may be small or concealed beneath forewings when wings are folded
Couplet 6
Leads to Ephemeroptera:
- Two or three tails
- Mouthparts inconspicuous
- Thorax without halteres
Leads to Couplet 7:
- Wings covered with scales or hairs, obscuring venation
Couplet 7
Leads to Couplet 8:
- Wings bare or with minute hairs; venation clearly visible
Couplet 8
Leads to Lepidoptera:
- Wings covered with scales (broadly flattened hairs)
- Mouthparts usually fitted with a coiled sucking tube (proboscis)
Leads to Trichoptera:
- Wings covered with hairs
- Mouthparts without a coiled sucking tube
Leads to Couplet 9:
- Antennae bristle-like and inconspicuous, usually shorter than head
Couplet 9
Leads to Couplet 10:
- Antennae of various shapes, conspicuous, and not bristle-like, and usually much longer than head
Couplet 10
Leads to Ephemeroptera:
- 2 or 3 tails
- Hind wings much smaller than forewings
Leads to Couplet 13:
- No tails
- Wings about equal in size
Couplet 13
Leads to Plecoptera:
- Tarsi 2- or 3-segmented
- 2 conspicuous tails (except reduced in some Nemouridae)
Leads to Couplet 11:
- Tarsi 5-segmented (except a few Hymenoptera have 3 or 4 segments)
- No tails
Couplet 11
Leads to Couplet 12:
- Abdomen broadly joined to thorax
- Front margin of forewing in basal half with many small veins perpendicular to edge
- Wings with more than 20 closed cells
Couplet 12
Leads to Hymenoptera:
- Abdomen with narrow constriction at junction with the thorax
- Marginal veins in basal half of forewing parallel to leading edge
- Wings with fewer than 20 closed cells
- Aquatic forms are very small, usually less than 3 mm long
Leads to Megaloptera:
- Hind wings pleated lengthwise, folded fan-like when closed
- Veins along back edge of wings usually with Y-shaped branches
Leads to Neuroptera:
- Hind wings not pleated, similar to forewings when closed
- Veins along back edge of wings forming many Y-shaped branches
Neuroptera
Leads to Odonata-Zygoptera:
- Wings held together above abdomen or only partly spread when insect is perched
- Eyes separated by more than the width of one eye
- Fore and hind wings similar in size and shape, each with a quadrangle instead of a triangle and subtriangle
- Males with 2 paraprocts
- Females with a fully-developed ovipositor, bearing styli
Leads to Odonata-Anisoptera:
- Wings held horizontally when insect is perched
- Eyes meeting middorsally or separated by a space less than the width of one eye
- Fore and hind wings dissimilar in size and shape, with hind wing considerably wider at base than forewing; each with a triangle and subtriangle
- Males with an epiproct which is either entire or bifid
- Females with or without an ovipositor
Start a Discussion of this Couplet
References
- Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.
Orders excluded
These orders of Insecta are not included in this key: Psocodea
Description of this key
This key allows identification to order of adult aquatic and semiaquatic insects. Be aware that some invertebrates you might find (including crustaceans, springtails (Collembola), and worms) are not included here. Adult aquatic insects generally have wings present, usually fully developed, conspicuous, and movable, and legs present.