by Joseph DeSisto
This is a pseudoscorpion. Depending on how you look at it, you might describe it as a scorpion without a stinger, or a tick with pincers. In fact, it is neither.
Pseudoscorpions are arachnids, like spiders, mites and, yes, scorpions. But unlike scorpions, pseudoscorpions are a) tiny, b) don’t have stingers and c) instead inject venom into their tiny prey through glands in their pincers (Weygoldt 1969).
To be more specific, the pseudoscorpion in the picture above is Chelifer cancroides, commonly called the house pseudoscorpion. This species is cosmopolitan — it often associates with humans and lives in buildings, where it feeds on the other assorted animals that dwell in the forgotten cracks and crevices. They are harmless, and do us a favor by keeping pests in check, although their domestic habits can lead to awkward encounters such as this one:
Many pseudoscorpions live on soil and leaf litter, or under the bark of rotting logs. Others have more restrictive habits: there are several species that specialize in living in honey bee hives, where they sneak about among honeycombs and bee larvae. What do they do in bee hives? Some species are beneficial. Others are decidedly not.
A grand total of 15 species of pseudoscorpions have been recorded in honey bee hives, most of them in the tropics (Gonzalez et al. 2008). Many species appear to live exclusively alongside honey bees, but hives have also been found to contain C. cancroides — remember, the one that always seems to turn up in places it shouldn’t.
At least one species, Ellingsenius handrickxi, is definitely not a bee friend — it regularly preys on the bees (Vachon 1954). Another species, Ellingsenius indicus, has been seen travelling about by clinging to the bees’ necks, which may prevent them from gathering nectar and pollen efficiently (Subbiah et al. 1957).
Most pseudoscorpions don’t eat bees, but instead prey on mites, waxworms, and other invertebrates that live in honey bee hives. This can benefit the bees, since some of these squatters rob the hive of its resources: precious wax and honey. Pseudoscorpions also eat bee parasites, including Varroa mites, which can destroy honey bee colonies and devastate beekeepers.
The big question is, can we use pseudoscorpions to help control the Varroa mite? At least some species can be efficiently bred in captivity (Read et al. 2014), and unlike many other predators, pseudoscorpions are comfortable living in groups — cannibalism is rare (Weygoldt 1969).
Several New Zealand entomologists are optimistic, among them Dr. Barry Donovan. He has published several popular and technical articles touting pseudoscorpions as having potential to control Varroa. His evidence is compelling — pseudoscorpions do eat Varroa mites. Video surveillance reveals they will even remove the mites from bee larvae for an easy snack (Fagan et al. 2012).
These voracious predators can eat up to nine mites per day, and Fagan et al. (2012) estimate that a population of only 25 pseudoscorpions is enough to control Varroa mites in a typical honey bee hive. So, it seems that pseudoscorpions could be an effective way to control Varroa. Donovan and Paul (2006) even suggest modifying commercial hives to provide “breeding sites” for pseudoscorpions.
It might not be that easy. A systematic study using the pseudoscorpion Ellingsenius indicus in the Himalayas revealed that although this species may eat Varroa, it prefers to eat bee larvae, non-parasitic lice, and the remains of already-dead bees (Thapa et al. 2013). This doesn’t contradict Fagan et al.’s study showing that pseudoscorpions do eat Varroa mites — Fagan et al used a New Zealand species, not E. indicus, but an unspecified pseudoscorpion.
What the Himalayan study does tell us is that knowing all the details, including the exact species relationships, is critical. Some pseudoscorpions are beneficial and eat mites straight off the bees, but others cut out the middle-mite and just eat the bees themselves. Most species probably do both. Pseudoscorpions may prove invaluable in the war against honey bee decline, but for now, there’s a lot left to learn.
Donovan, B.J. and F. Paul. 2006. Pseudoscorpions to the rescue? American Bee Journal 146(10): 867-869.
Fagan, L.L., W.R. Nelson, E.D. Meenken, B.G. Howlett, M.K. Walker, and B.J. Donovan. 2012. Varroa management in small bites. Journal of Applied Entomology 136: 473-475.
Gonzalez, V.H., B. Mantilla, and V. Mahnert. 2007. A new host record for Dasychernes inquilinus (Arachnida, Pseudoscorpiones, Chernetidae), with an overview of pseudoscorpion-bee relationships. Journal of Arachnology 35(3): 470-474.
Read, S., B.G. Howlett, B.J. Donovan, W.R. Nelson, and R.F. van Toor. 2014. Culturing chelifers (Pseudoscorpions) that consume Varroa mites. Journal of Applied Entomology 138: 260-266.
Subbiah, M.S., V. Mahadevan, and R. Janakiraman. 1957. A note on the occurrence of an arachnid – Ellingsenius indicus Chamberlin – infesting bee hives in South India. Indian Journal of Veterinary Science and Animal Husbandry 27: 155-156.
Thapa, R., S. Wongsiri, M.L. Lee, T. Choi. 2013. Predatory behavior of pseudoscorpions (Ellingsenius indicus) associated with Himalayan Apis cerana. Journal of Apicultural Research 52(5): 219-226.
Weygoldt, P. 1969. The Biology of Pseudoscorpions. Cambridge, Massachusetts: Harvard University Press.
Vachon, M. 1954. Remarques sur un Pseudoscorpion vivant dans les ruches d’Abeiltes au Congo Belge, Ellingsenius hendriekxi n. sp. Annales du Musbe royal du Congo Beige, N. S. Zool. 1: 284-287.