Thrastle

(Teratothrastus vorax Linnaeus) A small but extremely savage cave-dwelling predator and scavenger, formerly resident only in northern Europe, but now also present in small underground colonies on the East and West Coasts of North America.

The first references to thrastles appear in such early works as the "lost Physiologus" of the fourth century, the "interpolated" late-sixth/early-seventh century versions of the Etymologia of Isidore of Seville, and the eighth-century "lost edit" of Rabanus Maurus's compendium, De Universo. But the best descriptions, and much closer to us in time, come from the biologist Linnaeus's suppressed Bestiarium Ignotum, q.v. Linnaeus was as shocked by the thrastle's unbridled appetites as he was by its phylogenetic unorthodoxy: he changed his mind at least six times about whether it was a crustacean, a reptile or an insect, to judge by the marginal notes in the Bestiarium. (The story that Linnaeus's live specimen ate his notes at least once must be considered anecdotal. However, the rather cranky annotation "Mehercule is res est tempore mihi non valens"* can still be seen in the margin of the Bestiarium's original "thrastle" page, despite Linnaeus's later attempt to scrape it off the parchment.)

Thrastles have lived in the deepest caverns of Europe for many thousands of years. There are images of them in the famous caves at Lascaux and Chauvet-Pont-d'Arc. These drawings (perhaps fortunately) have routinely been mistaken by present-day paleoartistic specialists for badly-drawn pictures of heavenly objects, or just scribbles. The initial mistake is understandable: physically, the thrastle somewhat resembles various members of the Echinodermata, especially the "spiny stars". Like them, it has a small central body and a number of legs which can vary between four and twelve, depending on how many of them have recently been ripped off and eaten by other thrastles, or simply pulled off by the occasional (extremely lucky) escaping prey object. The legs are tipped with small venom sacs and needle-sharp injecting claws in clusters of three. The venom is a neurotoxin usually powerful enough to kill small prey outright, or at least to paralyze it until the thrastle can deal with it.

It is hard for a vertebrate not to be judgmental about the way thrastles eat, which -- again, as in some of the echinoderms -- involves enterocoely, or "sending your stomach out to dinner". The thrastle only uses its small rosette of teeth to pull its food into pieces small enough for the extruded stomach to enclose. The energetic digestive processes of the thrastle leave nothing but the most resistant substances intact: not even precious metals survive the process, as one part of the thrastle's cocktail of digestive juices is the nitric acid / hydrochloric acid mixture anciently known as aqua regia.

Probably because they evolved in such a food-poor environment, thrastles are intensely competitive, normally attacking one another viciously on sight. Thrastles are born hungry: if insufficiently nourished during the pre-hatch period, they will happily eat one another -- which is probably why broods are so large, numbering between one and three hundred. "Like a thrastle's nest" is one wizardly idiom for a nasty, tangled and generally unsavory situation which the finder would prefer to walk off and leave just the way it is. The idiom may also be a comment on the thrastle's breeding habits, about which probably the less said the better, and which were possibly one of the factors that made Linnaeus keep classifying them with some of the more relationship-challenged Arachnidae.

When disturbed in the normal cavern habitat, or if competition becomes too fierce, most thrastles will move out under cover of darkness and attempt to find another territory where they will not have to compete for food or breeding partners. In their original northern European range, this would often mean that they would shortly be found infesting the dungeons or cellars of the nearest castle, cathedral, or manor house -- or humbler places like the cavern "root cellar" or underground wine or beer storage vaults of some small village. It is probably from some such location that thrastles hitchhiked from the Old World to the New, eventually finding satisfactory new habitats in the cavern complexes of both North American coasts, and (somewhat later) in the subway systems of New York, Toronto and Washington D.C, where they thrive today. (SYWTBAW)

(Note: the "Thrastle" mentioned by the poet Andrew Marvell (1621-1678) in his long poem "Upon Appleton House: To Lord Fairfax" is not T. vorax Linn., but is rather a misspelling of an archaic word for the European song-thrush, Turdus musicus.)

See also: Acta Parabiologica: Phylogeny and magic: Subterranean ecologies; Unnatural History; Vestral ecosystems; Wizardly fauna (Europe).

• "Dammit, this thing's not worth my time..."