Heckgrammite

Kelly’s Field Notes

Common Name: Dobsonflies (larvae called hellgrammites)

Order:  Megaloptera

Family: Corydalidae

Genera: There are 9 genera of dobsonflies!

Species of Note (There are around 60 species of dobsonflies described!):

• Eastern dobsonfly (Corydalus cornutus) - found throughout most of the eastern U.S. south into Mexico and north into Canada.

• Western dobsonfly (Corydalus texanus) - found throughout the western U.S. from California and west to Colorado and Texas.

•  Corydalus ralphi - one of the newest species of dobsonfly to be discovered (2022), it was found in Venezuela.

• Protohermes costalis - found throughout China and Taiwan. 

• Nevromus austroindicus - found throughout southwestern India.

Description: 

Dobsonfly larvae are fairly long, growing over 8.9 cm (3.5 in) in length. They are sandy colored to brown or black. They have very prominent pincers at the end of their heads, spines along their sides after their legs, ending at the rear of the abdomen with two small hooked appendages which help them anchor their bodies in fast moving water.  

From large larvae come large adults! Dobsonfly adults are the same length as larvae with a 12.7 cm (5 in) wingspan. They have prominent heads, very long wings (Order Megaloptera = large wing) and long bodies in general. Females have short strong jaws that can draw blood while males have comically long jaws that are harmless. They use them to fight other males for territory, trying to flip each other over. Neither adult feeds.

Life Cycle: 

Female dobsonflies lay around 1,000 eggs on leaves hanging over streams, in three layers. The finished egg mass resembles bird droppings. It takes about 1 to 2 weeks for them to hatch, and only at night. The larvae plop into the stream and float/swim along until they find a rock to settle under. Larvae (called hellgrammites) are active hunters, feeding on other insect larvae. It’ll take around 12 molts to pupate and even then, those 12 molts could take at least 1 year and up to 3 to happen. When ready, they dig a hole into the sand and form a pre-pupa for about 14 days, then they spend another 7 to 14 days as a full pupa. 

Once dobsonflies reach adulthood they generally do not eat, though captive flies have been known to drink honey water and they have been found on fermenting bait traps. Adults are active at night but only live a short time. Males about 3 days, females 10.

Super Powers:

• Flight - They’ve got four wings and are ready to fly! 

• Strong jaws - females can draw blood if they bite you. The adult males have prominent mandibles.

• Swimming - hellgrammites live in fast moving streams and swim well. Larvae have gills to breathe underwater

Dobsonflies in Culture:

• Hellgrammites are commonly used as bait by fishermen - they are expensive at bait shops because they are difficult to catch.

• Hellgrammites are sensitive to water quality, doing well in clean unpolluted water. They are used as bioindicators of stream health.

• There is a DC Comics character named Hellgrammite. Amanda is not a fan. 

References:

Baldine, Marisa. “Dobsonfly Adults Are All Bark and No Bite.” Chesapeake Bay Program, 6 Sept. 2023, www.chesapeakebay.net/news/blog/adults-are-all-bark-and-no-bite. Accessed 25 Jan. 2025.

“Dobsonfly | Insect | Britannica.” Encyclopædia Britannica, 2020, www.britannica.com/animal/dobsonfly.

“Eastern Dobsonfly - Corydalus Cornutus (Linnaeus).” Entnemdept.ufl.edu, entnemdept.ufl.edu/creatures/misc/eastern_dobsonfly.htm.

Martins, Caleb Califre, et al. " After a decade, a new Venezuelan species of Corydalus Latreille (Megaloptera, Corydalidae, Corydalinae) is discovered." ZooKeys 1111 (2022): 339.

“Species Corydalus Texanus - Western Dobsonfly.” Bugguide.net, 2024, bugguide.net/node/view/492607. Accessed 24 Jan. 2025.

Wikipedia Contributors. “Dobsonfly.” Wikipedia, Wikimedia Foundation, 1 Dec. 2019, en.wikipedia.org/wiki/Dobsonfly.