Six-spotted fishing spider

These spiders are native to the Western Hemisphere and can be found throughout the contiguous United States and southern Canada, more common east of the Rocky Mountains and Great Plains. They have also been reported in areas ranging from Ontario to Maine to southern Florida and Texas, west to the southern panhandle of Alaska and south to the Yucatan Peninsula and Chiapas, Mexico. However, they are not commonly collected from southwestern states.[5]

They are semi-aquatic and live in wetland habitats such as ponds, lake shores, and they can also inhabit slow-moving streams. This can include the littoral zones of lakes and ponds as well as the more slow moving pools and edge zones of streams.[6] They can be found among emergent vegetation, rocks and other structures near the water, such as boat docks.[7]

D. triton are capable of capturing fish up to five times their body size, and they use venom to immobilize and kill prey. This species is diurnal and thus hunts during the day. They can wait patiently for hours until stimulated by prey. Potential prey include both aquatic insects, neuston organisms[8] and terrestrial insects that have fallen into the water, tadpoles, frogs, and small fish.[6] As such, they are one of the few spider species known to feed on vertebrate species.[9] One study conducted in central Alberta, Canada found that both juveniles and adults feed primarily on arthropods residing on fresh water surfaces and that diet varied considerably based on size, geographic distribution, and seasonal changes. Prey are typically caught while alive, and D. triton spiders are not repelled by sclerotization and metasternal secretions of potential prey. Juveniles tend to consume smaller prey than mature spiders do, especially females, who demonstrated a considerable lack of small prey capture, a trend attributed to the intense energy needs of yolk production.[9]

Prey detection is thought to arise through two different strategies - the use of tactile stimuli on the water surface and via eyesight. For the former strategy, the anterior two pairs of legs rest on the water surface and respond to the stimuli of ripples along the water surface. They are often seen with their legs sprawled out by the water while they are waiting for prey. They hunt by the water's surface in which they can walk on water and dive under up to 18 cm (7.1 in) to capture prey. Their good vision contributes to their success when diving to capture prey.[7] They capture underwater prey as well as prey that fall on the water's surface or travels on water, such as water striders. Visual stimuli, while used, are less important.[5]

As active hunters that stalk or ambush aquatic prey, D. triton spiders do not use their webs for prey capture. Nevertheless, silk plays an important role in adaptation to aquatic environments. Silk is used to construct trailing safety lines (known as draglines) used in movement across bodies of water, for example. As spiders reach sexual maturity, males and females use web construction in different ways. Females use their draglines to transport pheromones to attract potential mates while males use silk to build sperm webs and nuptial gifts. Females also use silk to envelop eggs in spherical egg sacs and create nursery webs to house newly hatched spiderlings.[10]

Researchers identified four categories of silk protein types in the silk of D. triton - aciniform, ampullate, pyriform, and tubuliform. Egg sacs contain two distinct layers. The outer layer is thought to protect eggs from water due to its unique elemental composition and hydrophobic characteristics.[10]

In this species, courtship is initiated via silk-based pheromones that come from females.[9] Research reveals that these female dragline hormones, which allow for long distance chemical signaling, persist on wet surfaces and water. Males follow female draglines in a lycosid-like manner on land and with an alternating form for rowing and pulling when the dragline extends over water. Due to the ability of the signal to persist in aquatic settings, pheromones are thought to be non- or mildly polar compounds, perhaps a lipid or steroid.[11]

Since males are generally able to escape female attacks after copulation, they are able to mate again. Furthermore, while males do not seem to discriminate between virgin and non-virgin females in courting, females are unlikely to mate a second time and exhibit aggressive behavior towards males after their first copulation.[9] Evidence from field observations in Alberta, Canada (mating behaviors may vary based on location) suggests that D. triton is protandrous, meaning that males that emerge earlier have greater access to the limited resource of virgin females, a mating system that resembles ‘scramble competition polygyny,’ where competition for mates takes the form of a race between competitors. Furthermore, males gain an advantage if they are able to copulate more quickly, allowing them to move on to another female. Females also gain an advantage from quick copulation as they are able to subsequently divert resources and energy to egg production over mating activities. As males likely cannot discriminate between mated and non-mated females, males may stay with penultimate stage females until molting to the adult stage, a phenomenon that closely resembles cohabitation.[12]

Pre-copulatory behavior after pheromone signaling starts with an announcement display where males signal with “leg-waving” (lifting and waving of legs in an alternating or synchronous pattern, likely a visual signal) and “jerks.” This preliminary period is known as “palpation."[9] The male approaches using his own dragline and initiates rapid tapping motions with the previously raised legs. “Jerks” involve irregular leg extensions that generate a double burst of concentric surface waves that emanate from his location (likely a vibratory signal). The female responds to the approaching male by “drumming” on a substrate, such as the water surface, and initiating her own slower form of leg waving. Afterwards, a prolonged period of mutual leg waving begins before copulation.[11]

For virgin females, male vibratory signals lead to females running towards the potential mate. However, mated females often “feign coyness” by waiting for males to approach before attacking them.[9]

Copulation occurs when males of the species insert one palp into the female. This is done only once during copulation and is accomplished by prying open the epigynum using the tibial apophysis as a lever.[12]

D. triton exhibit pre-copulatory cannibalism in which predation of males by females occurs prior to copulation, an extreme form of intersexual conflict in which there are no benefits to males of the species.[13] Mating trials indicate that virgin females attack in 20-30% of pairings and that success occurs up to 40% of the time.[14] Not only do males constitute a regular part of the female diet, but male population density also tends to decrease after the emergence of females.[13] The findings of one study demonstrate how pre-copulatory sexual cannibalism of D. triton supports the idea of the “aggressive-spillover” hypothesis in which pre-copulatory sexual cannibalism acts as a non-adaptive by product of voracity (aggression towards prey). Consistent with this hypothesis, females with the highest juvenile feeding rate were the most likely to exhibit pre-copulatory sexual cannibalism. While pre-copulatory cannibalism has been extensively studied for this species, females commonly attack males during and after copulation as well.[13]

The ventral surface of the body of D. triton is coated with a hydrophobic substance that allows them to stay afloat and run across water, an ability they use in both prey capture and predation escape.[5]

In Lovettsville, Virginia

D. triton species are able to determine the source of vibrations from up to at least 20–25 cm. The curvature of the wave and the amplitude gradient as the wave passes the spider are thought to be the primary means of determining prey/predator distance on water.[17]