Phidippus cardinalis is active from mid-summer to fall. Immature stages are pale yellow to reddish-orange with most (there is a brown female form) becoming bright red as adults. The group seen in the video inhabit a glacial sand plain where sweetfern (Comptonia peregina) and little bluestem (Schizachyrium sp.) are prevalent. This xeric habitat also has a large population of mutillid wasps whose wingless females (aka velvet ants or cow killers) are known for their particularly nasty sting. Edwards’ account of another red jumping spider, Phidippus apacheanus, and its apparent mimicry of these wasps mentions P. cardinalis and the possibilty that mimicry of velvet ants may be a similar adaptive response with this species. While it is likely the red color of P. cardinalis is associated with its mutillid mimicry, the color may also have been selected for by enhancing the spider’s cryptic defenses. In fall red is a predominant color in this habitat and is apparent in the dense tufts at the bases of the bluestem grasses (where the spiders often forage and seclude themselves) as well as in the leaves of blueberries and maples that lie scattered about on the ground. A dark red fungus is also common. Most obvious, however, are the numerous colonies of British Soldier cup lichens (Cladonia cristatella), sporting bright red cups in this season This presents the possibility that for P. cardinalis the color red functions to the spider’s advantage in the context of both mimicry as a warning to would-be predators and crypsis to help conceal the spider from predators.
Edwards, 1984

Massachusetts – First State / County Records