Last night, as I went to rehang my towel after my shower, I noticed this insect on the wall (please ignore the fact that we don’t really have a wall):
I left my phone at home today, so thanks to Jordan for sending these pics to me…these just needed to be posted. Not startled? How about this one for some scale?
Ok. I was a bit rattled. That thing was HUGE! Scout was in the bathroom with me and noticed it. She got it a little agitated so its mandibles were rather aggressively seeking something to sample. I went to fetch Jordan…he was unimpressed because he had seen it and taken these pictures much earlier in the day.
Here is the skinny on what this thing is:
A female Eastern Dobsonfly.
The eastern dobsonfly, Corydalus cornutus (Linnaeus), is one of our largest non-lepidopteran insects. Its larvae, known as hellgrammites, are the top invertebrate predators in rocky streams where they occur.
The hellgrammites live under stones or occasionally on snags where they feed on a variety of soft-bodied insects (often immatures of net-spinning caddisflies and blackflies) (McCafferty and Provonsha 1983). In captivity, they will feed on midge larvae or commercial aquarium fish foods such as freeze-dried tubifex worms or fish food flakes (Hoover et al 1988). Helgrammites molt (shed their exoskeletons) 10 to 12 times and require one to three years to complete their development.
When ready to pupate, hellgrammites leave the water and may pupate close to the water or travel up to 15 meters or more in search of a suitable site for pupation (Mangan 1994) – typically under a rock, log, or some type of debris that serves to maintain a moist environment. Exodus from the water of full-grown hellgrammites in a given location is fairly synchronous (within a few days). Voshell (2002) states that local residents along Virginia rivers report that thunderstorms trigger emergence of the hellgrammites – a phenomenon known locally as “hellgrammite crawling”. It is believed that the behavior is stimulated by the vibrations from the thunder.
Upon reaching a suitable site for pupation, the hellgrammite typically digs a cell in the soil with its legs and mouthparts and smooths the interior by pressing the sides of its body against the wall of the cell. Hellgrammites have no silk glands; consequently, there is no silk or cocoon lining the cell. After spending one to 14 days inside the cell as a prepupa, the hellgrammite sheds its exoskeleton to become a pupa. The pupal stage requires seven to 14 days after which the adult emerges and digs its way out of the cell.
Adult dobsonflies are short-lived (about three days for males and eight to 10 days for females). It is generally believed that they do not feed in nature[. ] The adults are active at night and are strongly attracted to lights. Otherwise they spend most of their time in thick vegetation near streams.
Dobsonflies are beneficial insects and should be conserved. Hellgrammites are prized as bait by fishermen (particularly for smallmouth bass) and are available for sale at bait shops in some areas. Because of the effort required to collect them, they are fairly expensive to purchase. Therefore, they may be subject to over-exploitation and their collection for sale is regulated in some states. Although, hellgrammites are great fish bait, they are rarely found in the stomachs of fish – probably because they spend most of their time under rocks where they are inaccessible.
Hellgrammites tend to be found in relatively unpolluted water. Therefore, they may have value in bio-monitoring studies (Voshell 2002). Perhaps their greatest value may be their contribution to biodiversity in their habitat as predators.
Pretty COOL! Last year, a salmonfly (aka stonefly). This year, a dobsonfly…the New River Valley is an interesting place to live!