Tigrosa

27 May 2023

Tigrosa means "fierce like a tiger"(Brady, 2012) and is an apt name for some of North America's largest wolf spiders. Though these are also some of the largest spiders in Minnesota, I rarely encounter them. They are longer-lived (like the Geolycosa from my previous post); females may live 2-3 years while males typically live a single season (Kaston, 1948). Both species build burrows, sometimes under rocks or logs, from which they emerge each night to hunt for prey. Both members of the genus have a pale yellow to yellow midline stripe on the carapace.

On iNaturalist, Tigrosa helluo is called the Wetland Giant Wolf Spider. As its common name suggests, it is associated with wetlands and lake edges though Kaston indicated it has been found in woodlands as well (1948). In this species, the coloration ranges from dull yellow to greenish brown (Kaston, 1948) but darker individuals do occur. The pale yellow midline extends from the anterior eyes all the way to the rear of the carapace (in most individuals). The femurs are typically dark or spotted but they lack the "tiger stripes" of T. aspersa. This species is known from 8 counties at this time from southern Minnesota north to Lake County along the Lake Superior shoreline. An example of a typical specimen can be found here: https://www.inaturalist.org/observations/122710979. A darker individual can be found here: https://www.inaturalist.org/observations/5280939.

On iNaturalist, Tigrosa aspersa is called the Woodland Giant Wolf Spider. It is the least known member of this genus in North America because it is the least encountered (Brady, 2012). This species is larger than T. helluo and was only recently added to the Minnesota spider list. The pale yellow midline is most pronounced at the anterior region of the carapace and fades toward the rear (Brady, 2012 indicates that it is only found in the ocular area, but firsthand experience suggests that trait may be variable). The femurs show pronounced "tiger stripes" of alternating, irregular black and pale yellow bands; this characteristic is absent in T. helluo. The burrow entrance may have a turret that incorporates straw or twigs (similar to Geolycosa) (Kaston, 1948). This species is only known from a single specimen found in Houston County which can be found here: https://www.inaturalist.org/observations/163305282.

Happy spidering!

Sources
Brady, Allen R. 2012. Nearctic species of the new wolf spider Tigrosa (Araneae: Lycosidae). Journal of Arachnology, 40 (2):182-208.

Kaston, B. J. 1948. Spiders of Connecticut. Bulletin of the Connecticut State Geological and Natural History Survey 70: 1-874.

Posted on May 27, 2023 03:40 PM by cheins1