Macrosteles clavatus (DeLong and Davidson, 1934)
Basis for Listing
The Caped Leafhopper (Macrosteles clavatus) is a small plant-feeding insect, endemic to the northeastern and midwestern United States. Its known distribution is limited to a 1915 collection from New Jersey (DeLong and Davidson 1934), a 1932 record from northeastern Illinois, and three records from Minnesota: two collections made pre-1942 in Pope and Kanabec counties (Medler 1942) and two collections from Town Hall Prairie in Wilkin County (Red River Prairie Subsection) in 1993 and 2004.
Very little is known about the ecology of the Caped Leafhopper. Most related species (subgenus Sonronius) are restricted to montane and boreal situations in North America (Beirne 1952). Because it probably overwinters as eggs deposited in plant stems, the species is vulnerable to prescribed fire, which may extirpate local populations if unburned refuges containing suitable native vegetation are not maintained. Details of the life history and host plant associations remain unknown. Further surveys for this species are needed in the few areas where it has been reported to gain more insight on its biology. Given the lack of records ince 1932 from elsewhere in North American and its current distribution restricted to a single known site within the state, the Caped Leafhopper was designated a special concern species in 2013.
The Caped Leafhopper is a small bright yellow leafhopper ~4 mm (0.16 in.) in length. It has a pair of small round black spots on the top of the head and a distinctive capelike brown to black marking (wide at both ends and narrow in the middle) that extends down the middle of the back when the forewings are at rest. Related species also have black spots on the head but have wings that are entirely pale yellow or black or with a more complex pattern of dark markings.
Biology / Life History
Not much is known about the life history of the Caped Leafhopper. Specimen collection records indicate that adults are present in June and July (pre-1942), and August (1993 and 2004: females only, indicating late in the season). Related species have one or more broods per year and overwinter as eggs deposited in the stems of their host plants. The only series taken in the Midwest (2004) was from tall forbs north and east of the conservation sign at Town Hall Prairie. Two European species of Sonronius (Macrosteles) are known to utilize fireweed (Epilobium angustifolium) and related plants as hosts, overwinter as eggs in plant stems, and complete a single generation per year (Ossiannilsson 1983; Nickel 2003).
Conservation / Management
The small number of locations for this species and the apparent isolation of the populations due to past habitat loss are the primary threats facing the Caped Leafhopper in Minnesota. This is aggravated by continuing prairie habitat destruction. Any prairie that is not protected by permanent dedication for conservation is at risk of destruction. Small colonies of the Caped Leafhopper are vulnerable to extirpation as a result of natural events (such as severe drought, hailstorms, disease) or human caused events (such as insecticide application and fire), as well as from the vagaries of normal population processes (genetic bottlenecks). Although this species is fully winged and capable of flight, its dispersal capabilities are unknown.
Even where protected, prairie in Minnesota is strongly susceptible to woodland encroachment (succession). Invasion by nonnative herbaceous species such as smooth brome (Bromus inermis) and leafy spurge (Euphorbia virgata) is also a serious threat. Prescribed burning to replicate the natural fire regime that created and maintained the tallgrass prairie is the usual management tool for preventing succession and for suppressing nonnative species. Although the life history of this species has not been studied, the Caped Leafhopper is probably similar to other species of the tribe Macrostelini in completing its entire life cycle on the aboveground parts of its host plants and remaining dormant from late fall to early spring. This would make it vulnerable to prescribed burning. Accordingly, the use of prescribed fire as a habitat management tool must be judicious. Repeated annual burning of individual units to reverse severe woody encroachment is compatible with the survival of this species only if an adjacent unburned refuge containing suitable grass hosts is continuously maintained. The effects of grazing and mowing on this species are unknown.
Conservation Efforts in Minnesota
The only recently confirmed population of this species in Minnesota occurs in an area protected by The Nature Conservancy. Information about maintaining suitable habitats for this species is available to land managers, most of whom are knowledgeable about the potential negative impacts of prescribed burning on the arthropod fauna of prairies and follow guidelines to ameliorate threats. There has been an effort to educate all land managers in this regard.
An extensive survey of Minnesota’s prairie remnants was completed in the 1990s, and the information about occurrences of the Red-tailed Prairie Leafhopper is incorporated into the MN DNR’s Natural Heritage Information System database. These data are routinely consulted for environmental review, which helps in preventing negative impacts to the species. However, very little survey or monitoring for this leafhopper has been conducted in Minnesota since the 1990s, and remedying this is an important task if conservation of this species is to be successful.