As somebody who grew up in Europe I was really hoping that enrolling in a graduate school in the US would give me a chance to see many organisms that are rare or completely absent from the Old Continent. And, sure enough, as soon as I arrived in New England I almost got into a car accident after spotting my first Virginia possum, I giggled like a little girl at the sight of Black vultures feasting on a roadkill (probably a possum), and almost had a heart attack from the excitement of finding my first horseshoe crab on a beach in Connecticut. But nothing could prepare me for what one evening came to the light of the house that I shared with my then girlfriend. It was a creature so spectacular and unlike anything I had ever seen before that it took me a while to even put it in a broad taxonomic context. “It’s a megalopteran!”, I finally managed to exhale. “Oh yeah, a dobsonfly”, said Kristin, “They are pretty neat.”
That was my first introduction to the genus Corydalus, a massive creature that fully deserves to be a member of an insect order christened Megaloptera, or Hugewings (I just made this name up, but I think it’s fitting; as far as I know Megaloptera do not have a single-word common name despite being a well-recognized monophyletic lineage). They easily attain a wingspan of 140 mm (5.5″) and in flight are more akin to bats than insects. The dobsonfly that came to our light was a male and thus carried enormous, tusk-like mandibles that gave him a menacing look.
But, like so many seemingly dangerous invertebrates, a male dobsonfly could not hurt anybody even if he really tried. The gigantic mandibles are for show only, and the animal barely has enough muscle power to open and close them; actually biting is completely out of the question. Males use these ridiculous implements in largely ritualized combat with their rivals, a slower, weaker version of the jostling display seen in stag beetles. But be careful with dobsonfly females – while the males carry a pair of chopsticks, these have a pair of powerful wire cutters that can easily draw blood from careless fingers. Dobsonflies don’t live long as adults and, other than drinking water or an occasional visit to a flower to sip some nectar, don’t feed, and die within a few days.
The genus Corydalus is represented by 34 species, found mostly in the tropical regions of the Americas, and only the Eastern dobsonfly (C. cornutus) reaches as far North as Canada, while two additional species can be found in the southernmost parts of the US. The mandibles are enlarged in males of most species in this and in a closely related genus Acanthacorydalis from E Asia, although in Costa Rica I once caught a male of another dobsonfly with exaggerated sexual traits, Platyneuromus soror. His head carried two strange plates that reminded me of the facial lobes seen in an old male orangutan. Why they have them is unknown as they do not appear to use them in any way during courtship or mating.
The larvae of dobsonflies are aquatic and are well known to fishermen as hellgrammites (or helgies) – large, wiggly insects that make excellent bait for bass and trout. They are predators of other aquatic insects, such as caddis flies. Interestingly, while most species prefer large, well-oxygenated bodies of water (and thus make good indicator species of water quality), larvae of some hugewing species are capable of developing in such unusual habitats as water accumulated in tree holes or the digestive liquid at the bottom of pitcher plants. Those species that live in seasonal bodies of water are capable of aestivation, burying themselves is mud cocoons to await the return of water (very much like the lungfish). Interestingly, dried larvae of Megaloptera are used in Japanese traditional medicine to treat emotional problems in children, they are also consumed as a snack Zazamushi (not very tasty, according to my friend Kenji).
Hugewings give the impression of being ancient and primordial, and for good reason. They date back to the Permian, and are probably direct descendants of some of the earliest holometabolan insect (insects with the complete metamorphosis). They used to be lumped with the Neuroptera (netwings), but there is good evidence for their status as a monophyletic sister group to the Neuroptera.