cave spiders

Cave fights for food: voracious spiders vs assassin bugs

Killing and eating of potential competitors has rarely been documented in the zoological literature, even though this type of interaction can affect population dynamics. In a recent publication in the open-access journal Subterranean Biology, Brazilian scientists presented their notes regarding the predation of an assassin bug by a spider in Neotropical caves. Underground, where food resources are scarce, such events might be possible as a result of ecological pressures imposed by the hostile environment, hypothesise the researchers.

Killing and eating of potential competitors, also known as intraguild predation, is a rare event that occurs only in specific situations such as severe scarcity of food resources, resulting in the competition between predators.

A recent paper in the open-access journal Subterranean Biology examines the case of a wandering spider species (Enoploctenus cyclotorax) seen to prey upon assassin bugs (Zelurus diasi) in a limestone cave in Brazil.

Even though such type of ecological interaction is uncommon, it is potentially important since it may decrease the competition between apex predators and thus, affect their population dynamics. Zelurus and Enoploctenus are voracious predators with a wide distribution in caves and epigean environment. Both of them have similar diets. In normal conditions, spiders reject assassin bugs as potential prey, so intraguild predation cases occur only in very specific situations.

From the perspective of the participants, intraguild predation is a dangerous strategy because the prey is also a predator, armed and capable to kill. However, in caves, this could be a very useful behaviour since food resources are scarce and have low density.

“This may be an important factor, maintaining the species in that challenging environment”, concludes lead author of the study Dr. Leopoldo Ferreira de Oliveira Bernardi.

The scientists suggest that probably prey scarcity has left little choice for spiders, and that’s why they ended up using unconventional type of prey in their diet.

Intraguild predation between female Enoploctenus cyclotorax and adult Zelurus diasi observed during the study.
Credit: Leopoldo Ferreira de Oliveira Bernardi
License: CC-BY 4.0

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Original source:

Bernardi LFO, Sperandei VF, Audino LD, Sena CH, Alves JA (2020) Notes on the predation of an assassin bug by a spider in a Neotropical cave. Subterranean Biology 33: 17-22. https://doi.org/10.3897/subtbiol.33.48292

Out of the darkness: A new spider found deep within an Indiana cave

Lead author Marc Milne in the Stygian River Cave and a male specimen of the newly described *Islandiana lewisi*

Spiders are ubiquitous within our forests, fields, and backyards. Although you may be used to seeing the beautiful yellow and black spiders of the genus Argiope in your garden, large ground-scurrying wolf spiders in your yard, or spindly cellar spiders in your basement, this new sheet-web-building spider is probably one you haven’t seen before. The reason is that it’s known from a single cave in the world, Stygeon River Cave, in southern Indiana.

The University of Indianapolis assistant professor, Dr. Marc Milne, described the rare species in the open access journal Subterranean Biology with the help of a University of Indianapolis alumnus, Elizabeth Wells, who illustrated the spider for the manuscript.

Sheet weavers, also known as dwarf spiders or money spiders, are minute creatures growing no larger than a few centimetres in length, which makes them particularly elusive. Their peculiar webs are flat and sheet-like, hence their common English name.

Female of the new species *Islandiana lewisi*

The new spider, Islandiana lewisi, is an homage. Milne was shown the spider by a fellow scientist, Dr. Julian Lewis, who noticed the critter on one of his many cave expeditions. In appreciation for his help, Milne and Wells named the spider after Lewis.

This is the fifteenth species in its genus (Islandiana) and the fifth known to live exclusively in caves. It has been over 30 years since the last species has been added to this group.

At about 2 mm in size, Islandiana lewisi is thought to feed on even smaller arthropods, such as springtails living in the debris on the cave floor. It is unknown when it reproduces or if it exists anywhere else. The spider is likely harmless to humans.

The collectors of the spider, Milne and Lewis, described the hostile conditions within the cave, which the new species calls home: “because the cave floods from time to time, the insides were wet, muddy, slippery, and dangerous to walk on without the proper equipment.”

Milne and Lewis found the spider in small, horizontal webs between large, mud-caked boulders in the largest room in the cave. It was collected in October 2016 with the permission of the landowner.

Milne hypothesized that he had collected something special, stating, “I didn’t know what the spider was at first, I just thought it was odd that so many were living within this dark cave with no other spider species around.”

After returning to the lab and inspecting the spider under a microscope, Milne initially misidentified the species. However, when he re-examined it months later, he realized that the species was indeed new to science.

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Original source:

Milne MA, Wells E (2018) A new species of spider (Araneae, Linyphiidae, Islandiana) from a southern Indiana cave. Subterranean Biology 26: 19-26. https://doi.org/10.3897/subtbiol.26.25605

Seven new spider species from Brazil named after 7 famous fictional spider characters

Several literary classics from the fantasy genre are further immortalised and linked together thanks to a Brazilian research team who named seven new spiders after them.

Spider characters from A Song of Ice and Fire, Harry Potter, The Lord of the Rings, The Silmarillion, H. P. Lovecraft’s The Call of Cthulhu and the children’s favourite Charlotte’s Web and Little Miss Spider each gave a name to a new small cave-dwelling six-eyed spider inhabiting northern Brazil.

Discovered in iron caves across the state of Pará, northern Brazil, the new species belong to the same Neotropical genus Ochyrocera. They are described in a new research article published in the open access journal ZooKeys by Dr Antonio Brescovit, Dr Igor Cizauskas and Leandro Mota – all affiliated with Instituto Butantan, Sao Paulo.

Interestingly, while all seven previously unknown species prefer staying in the shadows underground, none of them has the adaptations characteristic for exclusively cave-dwelling organisms, such as loss of pigmentation and reduced or missing eyes. They are classified as edaphic troglophile species, which means that they are capable of completing their life cycle away from sunlight, but are not bound to the deepest recesses. Often crawling near the surface, they can even be spotted outside the caves. To describe the species, the scientists collected about 2,000 adult specimens following a 5-year series of field collection trips.

The list of ‘fantasy’ spiders begins with Ochyrocera varys named after Lord Varys from George R. R. Martin’s book series A Song of Ice and Fire. Lord Varys is also known as the Spider because of his manipulative skills and ability to ‘weave’ and command his networks of eyes-and-ears across two continents.

The name of Ochyrocera atlachnacha refers to the Spider God Atlach-Nacha from the universe created by H. P. Lovecraft. Atlach-Nacha is a giant spider with a human-like face which lives in the caves beneath a mountain and spins a web believed to link the world with the Dreamlands.

Two species are named after spider characters from the classic works by J. R. R. Tolkien. Ochyrocera laracna is a species named after the well-known giant spider Laracna (Shelob in English) who attacks main characters Frodo and Sam on their way to Mordor in The Lord of the Rings’ second volume – The Two Towers.

On the other hand, the Brazilian spider’s sibling – Ochyrocera ungoliant – is linked to Laracna’s mother. Ungoliant appears in Tolkien’s book The Silmarillion, whose events take place prior to those of The Lord of the Rings’ second volume The Two Towers. According to the story, Ungoliant translates to Dark Spider in Elvish.

Another staple in the 20th-century fantasy literature, the Harry Potter series, written by J. K. Rowling, also enjoys the attention of the researchers. The species Ochyrocera aragogue is an explicit reference to the talking Aragog, who lives in the dark recesses of the Forbidden Forest. In the second volume of the series, Harry Potter and the Chamber of Secrets, he confronts Harry Potter and Ron Weasley.

The authors do not fail to pay tribute to much less violent spiders known from popular children books. David Kirk’s Little Miss Spider inspires the name of Ochyrocera misspider. The character is remembered with her words: “We have to be good to bugs; all bugs.”

The Ochyrocera charlotte species refers to Charlotte, the spider from E. B. White’s classic Charlotte’s Web who befriends the main character – Wilbur the pig.

It is highly likely that there are many species and populations of this group of spiders yet to be discovered in the Neotropics, since the lack of previous studies in the region. However, the area and its biodiversity are impacted by mining.

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Original source:

Brescovit AD, Cizauskas I, Mota LP (2018) Seven new species of the spider genus Ochyrocera from caves in Floresta Nacional de Carajás, PA, Brazil (Araneae, Ochyroceratidae). ZooKeys 726: 87-130. https://doi.org/10.3897/zookeys.726.19778