Look what I found this weekend: hellgrammites!😍
This bizarre, worm-like creature is known as a hellgrammite. Hellgrammites are the larval form of Dobsonflies (swipe through the images to see this insect’s adult form with a photo by Joe Bartok ). This species is Corydalus cornutus, the Eastern Dobsonfly. Found in healthy, rocky streams, these bizarre animals live underneath stones or snags and feed on a variety of soft-bodied, aquatic insects as well as minnows and tadpoles. Adults do not need to feed, instead focusing their energy on locating a mate. They have a short time to do so, living for only 3 to 10 days as adults. By contrast, the larvae take 1 to 3 years to complete their development, molting up to 12 times in the process. So, the larger hellgrammite I’m holding is likely a few years old! After completing larval development, the hellgrammite will emerge from the stream to burrow into nearby soil. There, it will create a pupal chamber, forming a pupa that will allow the insect to slowly develop into its adult form. Once the insect is ready, it will emerge as an adult and seek a mate.
The abdomen of the hellgrammite has 8 pairs of lateral, tactile filaments which are used to help sense their surroundings and protect them from predators. At the base of abdominal segments 1 through 7 are pairs of tracheal gills which help the insect to absorb dissolved oxygen from the water. You can see these tufts in the first video! 🥰 These larvae also have spiracles (breathing holes), allowing them to breathe out of water when necessary. When disturbed, the larvae will either bite defensively with their large, serrated mandibles or will curl into a ball (as seen in the second video). This hellgrammite was thankfully not interested in biting me at all, participating in our little mini photoshoot before I released him back into the stream.
These insects, along with other aquatic invertebrates such as caddisflies, stoneflies and mayflies, are great indicators of water quality and health. These insects do not tolerate polluted streams and therefor are not readily found in unhealthy waters. Have you found a hellgrammite before? Tell me about it in the comments!😊