Author Archive

Insect of the week – number 30

Friday, July 30th, 2010
Diradius vandykei

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.

Insect of the week – number 29

Friday, July 23rd, 2010
Zorotypus hubbardiPhoto credit: Arthur Evans

Zoraptera: Zorotypidae: Zorotypus hubbardi (Caudell, 1918)

This week’s insect, Zorotypus hubbardi Caudell, is one of only two species of Zoraptera known to occur in North America north of Mexico. The common name for this species is Hubbard’s angel insect. Its distribution ranges from Maryland and southern Pennsylvania west to southern Iowa and south to Florida and Texas.

Zoraptera is a very small insect order with only 34 extant species all belonging to a single genus (Zorotypus Silvestri 1913) (Hunefeld 2007). These termite-like insects are often found in old termite galleries, lumber mill saw dust piles, under bark, or in rotten wood. They are relatively small (2-3.5 mm in total length) and they are known to live gregariously. There are two distinct adult morphs within each species including Zorotypus hubbardi: 1.) blind and wingless 2.) with a pair of compound eyes, three simple eyes, and a pair of wings. Zorapterans have been noted to feed on fungal hyphae and spores, scavenge dead arthropods, and also prey on nematodes and other small arthropods (Hinojosa-Diaz et al. 2006). 

Zorotypus hubbardi was described by Caudell in 1918. It can be identified from other zorapteran species by a combination of character states including the oval shape of the cercus, presence of two prominent spines at the ventral margin of the hind femur, the shape of the male abdomen, and the shape of the male genitalia (Gurney 1938).

The length of the nymphal period of Zorotypus hubbardi is estimated to be 30-50 days and the adult lifespan is estimated to be around 30-40 days (Shetlar 1978). Adults are most active during spring and summer. Copulation involves a female climbing upon the dorsal surface of a male that is facing the same direction and uniting the genitalia. The female then continues to climb forward and drags the male partner leaving him upside down while their genitalia are still united. The mating process lasts about two minutes. A female may produce five to seven eggs in her lifetime (Shetlar 1978). 

Shetlar 1978(Shetlar 1978)

We have about 200 Zorotypus hubbardi specimens at the NCSU Insect Museum. These specimens come from 42 collecting events from different parts of North Carolina. They are stored in 80% ethanol.

Find out more:

Gurney, A. B. 1938. A synopsis of the order Zoraptera, with notes on the biology of Zorotypus hubbardi Caudell. Proceedings of the Entomological Society of Washington 40: 57-87.

Hinojosa-Diaz, I.A, E. Bonaccorso, and M.S. Engel. 2006. The potential distribution of Zorotypus hubbardi Caudell (Zoraptera: Zorotypidae) in North America, as predicted by ecological niche modeling. Proceedings of the Entomological Society of Washington 108 (4): 860-867.

Hunefeld, F. 2007. The genital morphology of Zorotypus hubbardi Caudell, 1918 (Insecta: Zoraptera: Zorotypidae). Zoomorphology 37(1): 135-151.

Shetlar, D.J. 1978. Biological observations on Zorotypus hubbardi Caudell (Zoraptera). Entomological News 89 (9-10): 217-223.