Citizen Scientists Spot New Spiders in Virgin Islands
Photographs uploaded to iNaturalist document burrowing spiders never before recorded in the U.S. Virgin Islands.
Updated on Nov. 7, 2026 in Environmental
Citizen scientists' photographs documented burrowing spiders never before recorded in the U.S. Virgin Islands, including one photographed on St. John in 2022 and another in the St. Thomas area in 2023. Javier E. Mercado tentatively identified the spiders as members of the genus Ummidia, though the species has not been determined.
Why it matters
The findings highlight how public observation platforms can reveal biodiversity gaps in U.S. territories. Confirming the records could expand the known spider fauna of the Caribbean.
The spiders measure roughly three-quarters of an inch and belong to the mygalomorph group, which resembles miniature tarantulas. Mercado's 2025 study identified 13 spider types not previously recorded for Puerto Rico and the U.S. Virgin Islands combined, while an unpublished manuscript flags at least 10 more possible new territory records.
The players
Javier E. Mercado
Mercado is a researcher who reviewed iNaturalist spider observations and authored a 2025 study identifying 13 spider types not previously recorded for Puerto Rico and the U.S. Virgin Islands.
iNaturalist
iNaturalist is an online platform where members of the public upload photographs of plants and animals, contributing to large-scale biodiversity records.
The details
Mercado reviewed thousands of spider observations from the Virgin Islands on iNaturalist, searching for animals that differed from those already documented in the territory. He based the tentative Ummidia identification partly on a saddle-shaped feature on the spiders' third pair of legs.
Timeline
A nature observer photographed a spider on St. John in 2022.
Another spider was photographed in the St. Thomas area in 2023.
Mercado's study was published in the Caribbean Journal of Science in 2025.
The U.S. Forest Service highlighted Mercado's study in October 2025.
Big Picture
The discovery demonstrates how iNaturalist observations are being mined by researchers to refine regional species inventories, a pattern that complements traditional museum specimen work. Such records can help map how spiders disperse across Caribbean islands, including through ballooning, which may explain their spread between territories like Vieques and the U.S. Virgin Islands.
Anyone who photographs wildlife and uploads it to iNaturalist can contribute to regional species records that researchers later verify. Confirming the spider identifications through specimen examination and DNA analysis will determine whether these records are formally added to the territory's species lists.
The takeaway
Public wildlife photographs can reveal species gaps that formal surveys miss, so uploading careful observations to platforms like iNaturalist can meaningfully aid science.
Further reading
Explore more in Environmental coverage for the wider context of biodiversity discoveries.
Source note: This article includes information reported by St. Thomas Source.
