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Tigrosa helluo is a species of spider belonging to the family Lycosidae, also known as wolf spiders. T. helluo was formerly known as Hogna helluo before differences between dorsal color patterns, habitat preferences, body structures, etc. were discovered. They can be found across the eastern half of the United States, primarily in the northeast section or New England states. They can also be found along the east coast and even as far west as Nebraska or Kansas. T. helluo can be found in many habitats within these states including woods, marshes, fields, and riparian areas. Typically, they prefer to live in wetter areas as opposed to dry environments. Normally, males will live for around a year and females will live for close to two years.

The defining characteristic of T. helluo is its brown carapace and distinct yellow stripe starting from its anterior eyes extending down the cephalothorax. The underside of the abdomen has distinct black spots that distinguish T. helluo from other wolf spiders. At an average size of around 17mm, T. helluo is one of the smaller wolf spiders. In addition, females tend to be larger than males.

Like other spiders of the family Lycosidae, wolf spiders are solitary and will live and hunt alone. Unless in the process of mating, T. helluo will remain alone. They are usually active at night and actively hunt prey then. In addition, T. helluo do not create webs, although females will make burrows under rocks or boards. Relying on their excellent eyesight and senses, T. helluo are great hunters.

In terms of interactions with humans, T. helluo is not very aggressive and will not attack unless provoked. Their bites do inject venom, however to humans, it is not medically significant. Pain and swelling will occur, but nothing more serious than that. Anti-venom is rarely needed.

Description

The average body length for Tigrosa can be 10-31mm for females and 11-24mm for males while for T. helluo, body length averages at 17mm. Compared to its close relative Tigrosa aspersa, T. helluo is much smaller. Its carapace consists of a brownish color contrasting with a distinctive yellow stripe that extends from the anterior eyes to the cephalothorax. Starting from the posterior median eyes, a set of fainter yellow stripes extend posteriorly. In addition, the underside of the abdomen is marked with several black spots. Patterns found on the dorsal side of the cephalothorax and abdomen are similar to those found on Tigrosa gerogicola, however the faint yellow stripes appearing on T. helluo do not extend as far. Black spots found on the abdomen of T. helluo are also not found on T. georgicola. Coloration in the legs differ between genders, males’ legs appearing yellow without distinct markings and females’ legs appearing reddish brown without additional markings or bands.

Habitat and Distribution

Habitat

T. helluo can be found throughout the United States. Primarily they reside along the east coast in the New England region but can be found along the entire east coast down to Florida. Further west, T. helluo resides in most states in the eastern half of the US. They can be found as far west as Kansas and Nebraska.

Distribution

As T. helluo can be found in a large variety of states, they can be seen in woods, marshes, and even grassy areas in northeastern states such as Connecticut. More specifically, their nests are often found under stones or boards in fields and woods except for males, as they are not found in nests. These nests consist of burrows lined with silk. However, in states like Florida or Mississippi, T. helluo can most often be found in wetter areas such as marshes or lakes.

Reproduction and Life Cycle

Mating for the T. helluo usually occurs in May or June. Males will live for just over one year while females will often live for around two years. For males, maturation will occur between May and September. Egg sacs will be made in May and also July. They can range from 8-12 mm in size (diameter). The eggs by themselves can appear tan or yellow and are around 1-2 mm in diameter. Females will carry these eggs in an egg sac on their back until they hatch. Even after they hatch, the female will continue to carry the hatchlings on their back until they mature enough to hunt by themselves. For females, maturation can happen anytime throughout the year. Once mature, females will begin to overwinter during colder months. Males typically will die before it gets too cold.

As T. helluo matures, it will molt periodically depending on nutritional intake in order to increase in size. The frequency of molting is based on its nutritional reserves. Individuals that feed more often will molt less frequently in their process of maturing.

Mating

Female-Male Dimorphism

T. helluo is sexually dimorphic, in this case, the two sexes dramatically differ in size. The females mature to be much larger in size. Typically, females will grow to weigh more than 300mg with carapace widths of around 6.5 mm while males will usually only weigh in excess of 200 mg and have carapace widths of around 4.5 mm.

Copulation

The process of copulation for T. helluo consists of a series of interactions between the male palp and the female epigynum. First, the male will mount the female such that they are facing opposite from each other. The underside of the cephalothorax is positioned against the dorsal section of the female’s abdomen. The male then will signal the female to rotate the abdomen by touching the anterior of the female abdomen. After this, the male will then use his palp to engage with the female’s abdomen and epigynum. The right and left palps will interact with the right and left sides of the epigynum. After the palp and epigynum are engaged, the male will expand his hematodocha, causing his embolus to go into the female copulatory duct. Semen is then exchanged. This whole interaction is called an insertion. During a single insertion, the male may also expand his hematodocha multiple times. However, it is more often only a single expansion per insertion. T. helluo will also engage in more than one insertion per copulation. Usually, one insertion will happen per side of the male palp. Copulation for T. helluo will last usually around 8 minutes.

Diet

Prey

Wolf spiders (Lycosodae) will typically eat different kinds of insects or even other smaller spiders. They are nocturnal so they will wait for prey and hunt at night. T. helluo can survive on insects such as crickets (Acheta domesticus), fly grubs (Sarcophaga bullata), cockroaches (Periplaneta americana), mealworms (Tenebrio molitor), and even beetles (Dermestes).

Effects of Diet on Survivorship

T. helluo is able to feed on a large variety of prey, and thus will usually enjoy a mixed diet of different insects, etc. A 1992 study done about the effects of polytypic vs monotypic diets on wolf spiders found that those raised on polytypic diets had significantly higher survivorship in addition to reaching sexual maturity earlier in the case of T. helluo. Certain body parts like the cephalothorax and legs were also significantly larger at maturity in the polytypic diet group.

Effects of Diet on Behavior

A 1999 study done on the effect of feeding on burrow construction for T. helluo reported that hunger level will significantly impact T. helluo’s behavioral decisions. In comparison to starved spiders, the well fed ones had a better nutritional state and made significantly more burrows. Since males do not make burrows, they were not included in the study.

Predators

Wolf spiders, while they are hunters, are also preyed upon by other organisms such as praying mantises, birds, wasps, small reptiles, and even other spiders. Lycosidae have fantastic vision and are sensitive to vibrations, so they use these senses to detect and evade predators. They also use speed and camouflage from their natural coloring to avoid predators. For T. helluo, females make burrows in places like underneath stones that can also function as a place to hide from predators. If it is needed, T. helluo can also bite its predators and inject venom.

Behavior

Hunting

T. helluo will typically have a couple different foraging sites in which they will switch between. Females will build burrows of silk and wait for prey to show up in their current foraging site. Males will typically roam around and wait for prey. Like all wolf spiders do, T. helluo are solitary hunters and will hunt alone, only meeting with other spiders to mate.

Chemical cues in hunting

A 2001 study done on chemical cues in T. helluo suggests that T. helluo is able to detect chemical cues from recently hunted prey. The spiders will show a preference for chemical cues that go with their most recently hunted prey.

Communication

While wolf spiders are solitary and don’t usually associate with others outside of mating, communication between each other does occur occasionally. Wolf spiders have some of the best vision out of all spiders, so they use visual cues such as waving their pedipalps to signal to each other for mating. They are also sensitive to vibrations, scent, and taste.

Bites

Bites to Humans

Wolf spiders are usually not aggressive and will not bite unless really provoked. They do also possess venom that will be injected due to bites. However, to humans, wolf spider bites are generally considered minor and not medically significant. Bites typically cause minor swelling and pain, but no severe complications. Antivenom is not usually needed to treat wolf spider bites.