Hemiptera: Hebridae: Hebrus concinnus Uhler, 1894
Thinking about that spongillafly last week reminded me of other interesting and somewhat rare species I’ve come across, so this week I cover another uncommon insect I collected during my tenure as a masters student: the velvet water bug, Hebrus concinnus. Actually, I don’t know if the individuals I collected were this species, but they were definitely Hebrus. I found them crawling across the surface of a pool at the bottom of a waterfall along the Buffalo National River.
Velvet water bugs typically spend their lives walking along the surface of water sources, usually near submerged or saturated vegetation, like mosses on rocks. They’re fairly small insects, usually 2-2.3 mm (for this species, anyway), and are thought to be predators of small invertebrates (perhaps small, semi-aquatic collembolans?). They’re called velvet water bugs because their bodies are clothed in a short, dense fur coat (setae) that repels water and gives them a dull, velvety sheen.
The NCSU Insect Museum currently has only 2 species of Hebrus, represented by 10 specimens. Five are H. concinnus nymphs, which were all collected on the same day in 1970, at a single locality: 3 miles south of Seven Springs, in Wayne County, NC. They were scooped up from clumps of sphagnum in a watery ditch. Clearly we need more specimens, from different localities and different times! According to Bobb (1974) one can find H. concinnus from Quebec to Peru, so it shouldn’t be toodifficult to collect more, as long as we’re looking in the right places.
Insect of the Week
Ellipes minutus, NCSU specimen (Photo taken by A. Ernst)
Orthoptera: Caelifera: Tridactylidae: Ellipes minutus (Scudder, 1892)
(Written by Trish Mullins with input from Andrew Ernst)
The genus Ellipes can be distinguished from other members of the family Tridactylidae by the extreme reduction of the hind tarsi which are found as a small flap hidden between the large hind tibial spurs. The genus also lacks the prosternal spur that is found in the genus Neotridactylus (1). A key to the New World genera of Tridactylidae is provided by Gunther (1975). Marjanyan (2007) provides a key to several families of Orthoptera based on the distinctive genual part of the apical portion of the hind femur in Orthoptera.
Most people are familiar with the larger grasshoppers, katydids, and crickets of the Orthoptera, but it takes a keen eye to see the much smaller pygmy mole crickets of the family Tridactylidae. Pygmy mole crickets are minuscule, usually about 12mm long. They burrow beneath the soil and live in sandy areas near water (1). Several species of Tridactylidae have fully developed wings in order to fly away to find new sources of water if their habitat dries up (1). However, Ellipes minutus has reduced wings, as the picture below shows. The species is edaphic, meaning it is confined to soil for the entirety of its life (3). The front legs are fossorial (modified for digging) with toothed tibia.
Ellipes minutus, showing reduced hind wings (Photo taken by A. Ernst)
Ellipes minutus is sometimes known as the minute pygmy locust, or pygmy mole cricket. Don’t confuse the pygmy mole cricket with the «mole crickets», which are in the family Gryllotalpidae, though they do somewhat superficially resemble the mole crickets. Ellipes is more closely related to the Acrididae (short-horned grasshoppers) and Tetrigidae (pygmy grouse locusts). Many orthopterists no longer call tridactylids «pygmy mole crickets» since they are not crickets and instead call them «pygmy mole grasshoppers» (1).
The species must live near a water source with a good supply of algae, as it is their main source of food. For this reason, Ellipes is most often found in wet areas such as swamps and marshes and the edges of streams and lakes (1).
Specimens have been collected soon after it rains. According to Deyrup (2005), if the sand is dry near the surface and damp a few centimeters under the surface, it may be possible to lure specimens from their borrows by watering the ground with a watering can. Yellow pan traps have recently proven effective in collecting tridactylids (2).
There are 124 specimens of Ellipes minutus in the NCSU Insect Museum, but all were collected before 1950! Interestingly, most specimens were collected by past professors of Entomology at NCSU. Specimens have been collected from Aberdeen, Clinton, Raleigh, Hendersonville, Burgaw, Wilmington, Balsam, Blantyre, Ft. Macon, Parmele, Montreat, and from Cabarrus County. The oldest specimens were collected in 1907 from Raleigh and Hendersonville. We encourage you to go out and collect some fresh specimens!!