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Costa Rica is one of the world’s richest countries in terms of its biodiversity. This includes the group of spiders belonging to the class Arachnida, which also includes scorpions, ticks (chiggers), mites and other lesser known groups.

There are more than 1800 species of spiders in Costa Rica, among them the so-called black widows. This group represented in Costa Rica by just three species is little known by researchers and it is only recently that people have begun to develop an interest in them.

These spiders can be found on all continents and make up 30 known black widow species around the world. Two of the three species present in Costa Rica may, in the future, be added to this list as two species new to science; the third species is widely distributed and its presence is known throughout the tropical world.

This group of spiders is characterized, among other things, by its large size in relation to other species of Black Widow. The female’s body can easily measure up to 13 mm and has a large globe-shaped abdomen. The males, for the most part, are smaller and their abdomen is quite a bit more slender.

There are other physical characteristics that help us to recognize black widows, but perhaps the most striking is the reddish colored hourglass-shaped marking located on the ventral surface (underneath the abdomen).

Your first thought might be: “how dangerous or how poisonous are Black Widows?”

That’s actually a tricky question to answer, because there are many different factors to consider in spider bites, including the person’s state of health, the persons size, male or female, the part of the body that has been bitten and the exact species involved.

It is also important to emphasize that all spiders have venom, which they use to hunt and eat. A very small percentage of spiders can be harmful to humans under special circumstances, for example in the case of people with allergies or in very small children.

The main function of venom in spiders is to paralyze their prey and help them to process or digest it. Therefore, the poison tends to be tremendously effective when used for this purpose and in this type of animal. In other types of animals that might be bitten, and that are not the ordinary prey of spiders, the poison may have various effects ranging from moderate toxicity to severe consequences that require hospitalization and medical treatment.

Some of the main victims of spider bites are young children, possibly due to their curiosity. In these cases it is worth bearing in mind that the reactions and effects caused by the venom of most spiders are as yet unknown and have not been studied in all species, as is the case in Costa Rica.

On many occasions, spiders are killed and it is very easy to “crush them underfoot”, but sometimes they are more valuable and interesting alive. Spiders such as black widows may spend their entire lives in a single place, hunting cockroaches, crickets, mosquitoes and other insects that are considered a nuisance, without causing any major trouble to household residents or pets.

Sometimes when we do not want a spider in our homes, all we have to do is simply move it outside into the yard or to some other place where it will not be a danger to anyone.

Spiders often consume their mates (males) and this is not necessarily an act of aggression or cruelty. In fact, the sacrifice of the male as food for the female may have a biological reason if we consider that, after mating and fertilization, the female will need to produce eggs and weave the sack, among other activities.

She will therefore need extra energy and eating the male may well provide the required energy. However, on many occasions, the male may leave the web without risk – it all depends on how well fed the female is.

Costa Rican Black Widow Spiders

With regard to the Costa Rican species, it is possible that two of these may be new to science, and for this reason we will refer to all three without giving them a scientific name. Instead, they will be considered and treated according to the area where they live.

1.The first of these species is known in Costa Rica’s dry North Pacific region and has been found in the mountains and plains of Guanacaste. It tends to weave its webs in window frames, warehouses and other artificial sites built by humans. This species is the largest of the three and has the most remarkable and attractive coloring.

2.The second black widow is also second in terms of its body size and lives mainly in the Central Valley, especially in Heredia, where it is very common and abundant. It is perhaps the best known species, although to date it has not been possible to gather sufficient information to confirm this.

For now, this species appears to be Latrodectus geometricus, which is widely distributed in all the world’s tropical areas.

Unlike the other two species, it is of a gray color with numerous markings of different colors, particularly yellow, white and brown. The ventral marking on the abdomen is a little less defined although still noticeable. This spider tends to be very abundant in places where it is found. Like the other species, it is often present in facilities built by humans.

It has been found with its webs in a wide variety of places, including bicycles, service counters in public buildings, the entrance to houses, windows, etc. Inside its web it builds a small refuge where it remains hidden waiting for its prey; when it detects one it quickly moves away from its refuge and tries to trap it.

This species makes spherical egg sacs with several protuberances that give it a very unique shape and appearance.

3.The third and last species is the smallest and the most recently discovered of the three. As with the other species, researchers are currently gathering more information to help with its identification and characterization.

This species is also black, but unlike the others it has no marking on the abdomen and only has the hourglass shape on the ventral area.

Curiously, this spider was not identified by specialists who work with these creatures, but rather by ordinary citizens living in San Jose. Based on their own interest and certain television programs, these people consulted experts about a possible black widow that lived in their homes.

It turned out that the spider that they inquired about was a black widow and was apparently of another species and a different population that is well established in various neighborhoods of San Jose such as Hatillos, Desamparados and Curridabat.

There may be more species that have not yet been discovered, so the next time your in Costa Rica, keep your eyes open, you may get to be on the Discovery Channel!