Habronattus calcaratus maddisoni Griswold, 1987
A Jumping Spider
Basis for Listing
Habronattus calcaratus maddisoni (a species of jumping spider) is known from the Cumberland Plateau up the northeast coast to Maine and as far west as Isle Royale, Michigan, and north-central Illinois. Minnesota specimens establish a new northwestern range limit for the species in the U.S., 200 km (124 mi.) further west of previous published records (Griswold 1987). There are only two known occurrences of H. c. maddisoni in Minnesota despite over three decades of survey effort by the Minnesota Biological Survey. Habronattus calcaratus maddisoni was listed as special concern in 2013.
Jumping spiders are one of the most recognizable types of spiders as they generally have a stout body, rather short legs, a very large set of eyes, and the ability to jump. Their body shapes and colors often imitate prey such as ants and beetles. Habronattus calcaratus maddisoni is one of three subspecies of Habronattus calcaratus described on the basis of geographic variation by Griswold (1987). The others are H. c. calcaratus, which is known from Florida, and H. c. agricola, which is known from the Great Plains (South Dakota to Texas). Male Habronattus spiders often have modifications to their legs that aid in identification, though H. c. maddisoni is not distinguished in this regard. Habronattus calcaratus maddisoni males are strikingly patterned on their abdomens with two dark crescent shaped areas divided by a lighter colored stripe running lengthwise. The posterior half of the cephalothorax has the reverse of this, a dark central band flanked by pale ones. The anterior portion of the cephalothorax has a striking reddish-brown vestiture ("scales") that looks kind of like a "rug". Although the female is brown with grey legs and not easily identified in the field, some have a very similar vestiture on much of the cephalothorax and on the abdomen as well. Males have completely dark areas surrounding the eyes and mouthparts (chelicerae).
The only two occurrences for H. c. maddisoni in Minnesota are in St. Louis County (Border Lakes Subsection). The first specimen was found near Lake Vermillion by sweeping sumac, grass, and aster on a small ridge-top. A second specimen was collected by hand from an old quarry. Both collection sites were cliffs capped by a layer of vegetation. The cliffs act as barriers to aerially-borne spiders, effectively trapping them at the time of dispersal. The aerially dispersing spiders are stopped by the cliff wall; they then crawl upwards into the vegetation. The Lake Vermillion site is a type of fire-dependent forest, specifically northern dry-bedrock pine (oak) woodland.
Biology / Life History
Very little is known about the specific details of the biology and life history of this species, but it shares a number of general traits with other species in the group.
Jumping spiders do not spin webs for catching prey. Instead, they construct small tent-like silken retreats under rocks or logs or on plants, which they use at night and during hibernation. The females also lay their eggs in them. Jumping spiders are most active during the day, and they prefer sunshine. They tend to stay in their retreats on cloudy or rainy days. Jumping spiders are generally interested in whatever approaches them and will often turn and face human observers and may even advance towards them. They are generally harmless to people.
Conservation / Management
New genetic techniques are allowing scientists to re-examine how some species of jumping spider have been classified in the past, and groups like H. calcaratus are especially interesting since they appear to have geographically distinct subspecies to compare with each other. Differences in morphology and habitat patterns can help show how the species has evolved and colonized different areas over time and also demonstrate the continuing evolution of this species. It is interesting to note that a second subspecies, H. c. agricola, is known from South Dakota but not yet known from Minnesota. We may be able to document an overlap in range or a hybridization area in the western part of Minnesota that will be particularly interesting to arachnologists and evolutionary biologists.
Conservation Efforts in Minnesota
Surveys are ongoing to determine the distribution of this species in Minnesota.