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.

  Description

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). 

  Habitat

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.

Jumping spiders have four pairs of eyes with the large principal pair giving them better vision than other spiders. The forward-looking placement of this pair of eyes provides binocular vision enabling them to judge distances accurately, and they are able to identify prey, predators, and mates from up to 30 cm (1 ft.) away (Weber 2002). Physiological and behavioral experiments have demonstrated that they have color vision, possibly extending into the ultraviolet range.

Jumping spiders feed primarily on insects, though some may feed on web-building spiders. They will also feed on other jumping spiders, usually those that are smaller than themselves. Jumping spiders actively stalk their prey instead of snaring it in a web. They may, however, steal insects snared by the webs of other spiders. Jumping spiders hunt primarily during the day, using their keen eyesight to locate prey. Having spotted a potential quarry, a jumping spider will slowly stalk the prey until it is within jumping distance. Then it lifts its front legs and pounces. Like all spiders, jumping spiders move their legs not by muscular contractions but by changing the pressure of the fluid within them. This hydraulic system enables them to jump up to several times their body length without having large muscular legs. Before jumping, the spider always affixes a silk safety line to whatever it is jumping from; in case it falls, it can climb back up this tether.

The same visual capabilities that are critical to jumping spiders’ success as hunters also support complex courtship behaviors. Males often differ in appearance from females and can have colorful, sometimes iridescent, modifications to their bodies, front legs, or mouthparts. The parts of the male's body that are used in courtship are often conspicuously colored. In many jumping spider species, the males perform courtship dances in front of the females that are species specific. The male's movements range from a slight lifting of a leg to complex movements such as bobbing their bodies, twitching their abdomen, performing zig-zag movements, waving their front legs, or flashing their mouthparts into the eyes of the females. Some male jumping spiders also have auditory signals that, when amplified, sound like buzzes or drum rolls. It is presumed that females choose mates based on their courtship dances. After mating, females lay their eggs in their silken retreat and often guard their eggs and newly hatched young.

  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.

  References and Additional Information

Ehmann, W. J. 2011. Reconnaissance for state-listed jumping spiders (Araneae: Salticidae) in St. Louis and Lake counties, Minnesota. Final Report submitted to the Minnesota County Biological Survey, Minnesota Department of Natural Resources. 11 pp.

Foelix, R. F. 1996. Biology of spiders. Second edition. Oxford University Press, New York, New York. 336 pp.

Forster, L. M., and M. R. Forster. 1999. How do jumping spiders catch up on their prey?: a model for pursuit behaviour. (Araneae; Salticidae). Preliminary Draft, 06 Aug 1999.

Griswold, C. E. 1987. A revision of the jumping spider genus Habronattus F. O. P.-Cambridge (Araneae: Salticidae), with phenetic and cladistic analyses. University of California Publications on Entomology 107. University of California, Berkely. 344 pp.

Maddison, W. 1994. Jumping spiders of America north of Mexico [web application]. Tree of Life web project, University of British Columbia, Vancouver, Canada. <http://tolweb.org/accessory/Jump>. Accessed 16 Aug 2006.

Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.

Richman, D. B., and B. Cutler. 1978. A list of the jumping spiders (Araneae: Salticidae) of the United States and Canada. Peckhamia 1(5):82-110.