Subject: What’s this winged insect?
Location: Southern Idaho. (Irrigated land)
January 30, 2014 12:52 pm
I snapped a few photos of this insect with upright laced type wings. Then I posted the photo on FB. Of course the first question was, ” What is it?” I searched the internet to no avail other than I believe that it is in the family Neuroptera. Can you help me identify it?
First off, Neuroptera is an order, a broader classification than a family. Your Mayfly is in the order Ephemeroptera, which according to BugGuide, originates from the: “Greek ephemeros ‘of/for a day; short-lived’ + pteron ‘wing’ — refers to the short-lived adults ['ephemeros' comes from epi 'upon' + hemera 'day'].” Your individual is in the genus Hexagenia, and the common names are “Burrowing Mayfly, Giant Mayfly, Golden Mayfly” according to BugGuide. Mayflies are unique in that the adults or imago undergoes two molts. The larvae of a Mayfly is aquatic and is known as a nymph or a naiad. Upon reaching maturity, it leaves the water and molts, emerging as a winged pre-adult or subimago. Shortly afterward, it molts a second time, emerging as a full adult or imago. These Giant Mayflies are also prized bait for anglers who fly fish. According to BugGuide, the anglers even distinguish between the subimago that has “wings cloudy in appearance, body dull and pubescent, with appendages somewhat shorter — but otherwise similar to imago” of a Mayfly which they call a dun and an adult that is called a spinner which has “wings usually transparent but sometimes patterned, held vertically and together above thorax when at rest”. Since the wings appear cloudy, we believe this is a subimago. Compare your individual to this image on BugGuide. The position of the body of your Golden Mayfly conforms to BugGuide’s description: “front legs often held forward and sometimes upward in front of head when at rest.” Because of your northern location, we are speculating that this Golden Mayfly is Hexagenia limbata and you might enjoy reading more about it on TroutNut. We are going to contact Eric Eaton to see if he can provide any additional information.
This giant mayfly is from southern Idaho, so I am guessing Hexagenia limbata, but BugGuide’s descriptions have me a bit confused. The wings appear cloudy, so I would guess subimago, but the front legs are held in the position BugGuide indicates is used by the imago. So, which is it? Imago or subimago? I lean subimago
Eric Eaton Responds
I am not an expert on aquatic insects *at all,* so I’m hesitant to make a definitive statement. I agree with the genus-level ID at the least.
It might be a subimago, especially if there is no shed exoskeleton close by. Otherwise, it could be a freshly-molted imago. The subimago emerges from the nymphal exoskeleton right on the water or very close by. The imago emerges later, usually on vegetation, often some distance from water.
Often we are asked to identify the exuviae of Mayflies, and when they are on the sides of homes, they definitely were left by the subimago after the final molt.