A few of my smaller, failing fire ant colonies are infested with tiny crawling things. In the spirit of curiosity (and getting these things out of my lab colonies) I finally put them under a scope to try to figure out what they were. Turns out they’re actually rather pretty close up. They’re also a member of what may be the most abundant arthropod in the world. Springtails (class Collembola) are tiny, easily overlooked, and almost everywhere. Primarily detrivores and microbe-eaters, they mostly inhabit leaf litter, with an average square meter of topsoil containing upwards of 40,000 individuals (Hopkin 1997).
Collembolans are one of three groups of hexapods (six-legged arthropods) that are not considered part of class Insecta. Unlike the later derived insects, they are wingless and entognathous (have mouthparts retracted into the head). Collembolans take their common name “springtails” from a unique bit of morphology that allows them to jump 20 to 100 times their height in a fraction of a second. This structure, a long forked prong called a furcula, tucks under their body into a clasp and releases like a spring, launching them into the air. In person it looks sort of as if they are vanishing and appearing elsewhere in the tray, like tiny buggy teleporters. It is easy to understand why these organisms are sometimes claimed as the source of delusory parasitosis–a condition which cause people to falsely believe they are infested with parasites.
These particular springtails have the characteristic appearance of the family Entomobryidae, the slender springtails. I was curious to know more about the infestation of crawlies eating the dead crickets and ant detritus in my lab so I also threw a picture onto BugGuide, where I was rewarded with a species ID a day later. They are Seira bipunctata (det. thanks to Frans Janssens).
Unfortunately, little non-taxonomic information appears to be available on these guys, although the genus Seira is distributed throughout North America, as well as most of the world. My personal observations are that they appear to be detrivores, fairly active, and the mid-sized ones seem to leave their furculas extended and also wiggle them at me when poked. I don’t know; poking things to see what they do is pretty much my go-to technique as a scientist.
One final note: One of the scientific papers I read while researching this post used the phrase “the collembological community” to describe springtail researchers. “Collembological” is now my new favorite word.