Embioptera: Teratembiidae: Diradius vandykei (Ross, 1944)
This week’s insect, Diradius vandykei Ross, is a webspinner that is found throughout North Carolina’s Coastal Plain. It is distributed in the Gulf Coast Plain (from south Mississippi to Florida) and the coastal plains of Georgia, South Carolina, North Carolina and southeast Virginia.
Diradius vandykei is one of less than 400 currently recognized species of Embioptera worldwide. It belongs in the family Teratembiidae and the genus Diradius. There are only three species (including D. vandykei) of Diradius found in the United States. Diradius can be identified by the presence of two prominent inner lobes in the left cercus-base (left cercus-basipodite) in adult males. Diradius vandykei is distinct from the other two Diradius species in that the anterior angles of the submentum are lobed (lobe at each anterior angle) and a tooth is present in the incisor arc of the right mandible (Ross 1984).
Webspinners in general are known to live gregariously under rocks, in soil, and on or under bark. They construct silken galleries using silk produced from silk glands present in the basal segment of the front tarsus. These galleries are continually expanded and covers foraging zones as individuals seek fresh food such as lichens, algae, and dead plant matter. Many records of Diradius vandykei are from the trunks of isolated, lichen-encrusted hardwoods (especially oaks) and from pines (Deitz and Stephan 1984).
Other interesting facts about webspinners include their ability to move backwards with agility and their ability to fold their wings (males) forward. Winged males can run backwards through galleries without damaging their wings. These flexible wings are stiffened up for flight by inflation of the hollow veins in the wings with hemolymph. Some species of webspinners have also been observed to play dead when facing potential danger.
We have well over 200 Diradius vandykei specimens from over 40 collecting events at the NCSU Insect Museum. Most of these specimens were collected in North Carolina. We also have numerous vials of undetermined Teratembiidae (many of which are possibly Diradius vandykei). They are stored in 80% ethanol.
Find out more:
Deitz, L. L. and D.L. Stephan. 1984. Records of Diradius vandykei (Ross) in North Carolina and Virginia (Embiidina: Teratembiidae). Proceedings of the Entomological Society of Washington 86 (1): 239-241.
Miller, K.B. 2009. Genus- and family-group names in the order Embioptera (Insecta). Zootaxa 2055: 1–34.
Ross, E. S. 1984. A synopsis of the Embiidina of the United States. Proceedings of the Entomological Society of Washington 86 (1): 82-93.
Szumik, C., J.S. Edgerly, and C.Y. Hayashi. 2008. Phylogeny of embiopterans (Insecta). Cladistics 24: 993-1005.