UV reflection

Males utilize their ability to reflect UV light as a mating call. The levels of “glow” on the male abdomen create varying interest among the females.^[4] The females are much more attracted to the glowing males in comparison to the males that have their UV reflection ability masked. However, it is probable that non-UV reflecting males have not been eliminated by evolutionary pressures because of their advantage of being inconspicuous to predators.

Web

Cosmophasis umbratica do not traditionally spin webs like most other species.^{[2] [7]}On the other hand, due to their extensive eye depth and powerful vision, they have adopted a “stalk and leap” strategy. These spiders have even been referred to as the tigers of the spiders.

Cosmophasis umbratica build nests made of viscid silk for them to rest and retreat into. Their nests look similar to sheets made of silk with tubes on either side. Their nests tend to have wide openings with narrow “entry points”. ^[8] Both males and females tend to build similar features for their nests; however, females tend to seal their doors much more than males do.^[1]

Prey

With their unique UV reflection, the spiders rely heavily on their vision to hunt. They have a complex visual system that acts as their guidance when it comes to terms of prey. Their eyes can recognize objects that are about 20-30 feet away. They also have another set of eyes that help them detect long-range movement. Their two sets of eyes allow them to escape predators in an efficient manner as well as catch prey in a strategic way.

Furthermore, these spiders are known to be nectivorous. They feed off of the sweet nectar of the lxora plant. This species also feeds off of insects, including flies and crickets.

Life cycle

After mating, the female C. umbratica holds the sperm until she is ready to fertilize and lay her eggs. The mother will create an egg sac made of silk that will protect the eggs throughout their development, which is a behavior observed in many spiders. As the eggs are woven and hidden inside the silk, they stay there until fertilization occurs. The mother will lay anywhere from two to thirty-six eggs.

Although some spiders may lay there woven sac in a secure location, the mother C. umbratica carries her sac with her until her egglings hatch in order to protect them. When the eggs are ready to hatch, spiderlings emerge

Reproduction  

Males become sexually mature before females. They are on the hunt for a suitable partner earlier on. During male to female interactions, skittering is one of the main ways to attract a female. Females tended to be drawn to the level of excitement the males displayed. Therefore, in the presence of females, males became eager and move their bodies back and forth. As the male attempts to mate with a female, there is a lot of decamping taking place. When a male faces the female and she doesn’t decamp, then the male will continue to skitter alongside her grabbing her attention. Furthermore, the male will drum and his posture straightens and he flexes his abdomen and displays his UV light.

Sometimes, the female will try to gain the male’s attention. This is done by bending the abdomen and prodding onto the male. There is a game of “tag” between the male and female as one tries to grab the attention of the other. The females generally try to avoid the attention of the male for as long as possible before entertaining the male.

The coupling time varies between each of the C. umbratica. Almost all couplings end with the females scurrying away. Females will not have just one partner throughout their lifespan.

Consequences of sexual dimorphism

The colorful bodily array on the spiders may benefit the males in terms of sexual selection. However, quite contrarily, the males do in fact have pay for it. The UV reflecting individuals can be easily spotted by predators. The level of attraction may increase potential mating options but it also increases the rate at which there are predators. The predators notice the glow that is embedded in the bodies of the males and if a predator were to have good eye sight, they’re able to spot the UV light from great lengths away.

Male-male interaction

Most often, when two males interact with one another, it usually involves a fight of some sort. These interactions usually behind when the spiders about 10-15 cm away from the other. They each separately raise their bodies, have their legs hunched, and they bend their abdomens facing one another. They start slowly coming towards one another and their palps begin to vibrate. Once they are about 2-3 bodies within each other, they begin to lunge at each other with their legs forward and elevated. Traditionally, after an initial altercation, one of the spiders will decamp and the other will chase the decamping spider. For the most part, the bigger spider will win the fight; however, if both spiders are similar in size than the spiders will extend and retract their legs at each other for a longer period of time. Eventually, one male will turn out to be successful in the fight and they will be deemed the winner.

Venom

Cosmophasis umbratica are known to be harmless to people and do not tend to bite individuals. The spider’s venom is harmless and non poisonous  unless one is allergic to spiders in general. There should not be any risk of getting bitten by C. umbratica. Even if one were to attack and try to kill these spiders, very rarely would these spiders bite as they are traditionally considered non-violent. These C. umbratica are known to be one of the 'kindest' spiders in the world.