Phidippus apacheanus Chamberlin and Gertsch, 1929
A Jumping Spider
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Basis for Listing
Phidippus apacheanus (a species of jumping spider) is a common species in the southern United States from Florida to California. However, it appears to be of local occurrence north of 30° to 35°N latitude. The species' late maturing dates (August/September) probably plays a role in limiting its distribution further north. It is rare in the Upper Midwest, known only from a few locations in southwestern Wisconsin and southeastern Minnesota. In Minnesota, the species is limited to undisturbed native prairie, a rapidly diminishing habitat type (Minnesota's Remaining Native Prairie). Phidippus apacheanus has been collected at just three sites in the state, the most recent being from 2010. Becaue the habitat for this species in Minnesota is so rare and vulnerable, P. apacheanus was listed as a species of special concern in 1996.
Adults are often greater than 1 cm (0.4 in) long. The dorsal surfaces of the cephalothorax and abdomen of males are clothed in bright scarlet scales, contrasting sharply with the glossy black of the rest of the body and the legs. The chelicerae (a pair of large fang-tipped mouthparts forming the lower half of the spider’s facial aspect) are an iridescent greenish blue. Females are similar, but a more orange color often replaces the scarlet, and there may be a central area of the abdomen that is black. The legs of females may have red or orange rings at intervals along them. According to Edwards and Hill (2008), the coloring of these spiders may mimic that of mutillid wasps (also called velvet ants), which are wingless, ground-dwelling wasps with vicious stings. Males of the related species Phidippus pius may resemble this species, but the scaling is a duller orange and less complete, with dark patches on the cephalothorax and a pair of longitudinal dark bands along the middle of the abdomen.
In Minnesota, P. apacheanus is known only from the southeastern corner of the state (The Blufflands) in dry prairie, a diminishing habitat type (Minnesota's Remaining Native Prairie). Elsewhere, the species has been found in a variety of open habitats including sagebrush flats in Utah.
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 use silk to 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 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; 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 feed on other spiders. They will even 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 find prey. Having spotted their 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 may 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 that are specific to that species in front of the female. 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 the males’ courtship dances. After mating, females lay their eggs in their silken retreat and often guard their eggs and newly hatched young.
Conservation / Management
As with other prairie-dependent arthropods, the survival of P. apacheanus in Minnesota requires the active management of the remnants of its habitat. Periodic wildfire was the primary agent preventing invasion of trees in the pre settlement prairie landscape, and prescribed burning is the standard management tool to achieve this in remnants. Because fire is lethal to the spiders, managers must apply it strategically to avoid extirpations. And because the distance between remnants probably prevents recolonization, these extirpations could accumulate, eventually eliminating the species from the state. Fire management must include division of sites into multiple burn units and rotation of burning among them on a schedule that assures adequate survival of each burn for population recovery and enough time between burns for recovery to occur.
Seed harvesting from prairie remnants to support recreation of prairie habitat is another potential threat that can be ameliorated with a strategic approach. Females of this species spin silken "retreats" in the seed-bearing structures of some prairie forbs, wherein they lay and guard their eggs. Accordingly, removal of these structures for seed harvest should never be total, and the"leave' plants should be widely distributed, not confined to one or a few small stands.
The few Minnesota records of P. apacheanus are at the northern limit of the large range of the species, affording the opportunity to investigate this spider's ecological tolerances. Although remnants of natural areas may often be too small or isolated to maintain populations of some rare vertebrates, they may be suitable for maintaining invertebrates. Benign to humans, diverse, colorful, and behaviorally complex jumping spiders may be good ambassadors for their kin and invertebrates in general.
Best Time to Search
The best time of year to survey for P. apacheanus is from August through September.
Conservation Efforts in Minnesota
Surveys of the two previously documented sites for P. apacheanus conducted in early summer 1996 were unsuccessful at relocating this species (Ehmann and Boyd 1997), as were surveys in Wabasha County in 2015. Because all records are from sand prairie habitats in extreme southeastern Minnesota on the Paleozoic Plateau, the unsampled counties of Goodhue, Houston, and Olmsted should be priorities for survey effort. Late-season sampling, including hand searches, may yield new records. Any new records, including date of collection, behaviors observed, and habitat details will be of high interest.