Pygidial-glands
Guides
Brachinus vulcanoides
Brachinus vulcanoides is a species of bombardier beetle in the ground beetle family Carabidae, first described by Erwin in 1969. As a member of the genus Brachinus, it possesses the characteristic defensive chemical spray mechanism that defines this group. The species is known from North America, specifically recorded from the United States, though detailed natural history information remains limited in the available literature.
Dianous
Dianous is a genus of rove beetles in the subfamily Steninae, characterized by their specialized ability to glide across water surfaces. All representatives of this genus possess pygidial glands that secrete alkaloid and terpene compounds, including stenusine and related molecules, which reduce water surface tension to enable rapid skimming locomotion. The genus has been documented across Europe, Asia, and North America, with particular taxonomic attention in China and Turkey where multiple new species have been described in recent years. Dianous species are specialist predators of small invertebrates.
Gyrinus
whirligig beetle
Gyrinus is a genus of small aquatic beetles in the family Gyrinidae, commonly known as whirligig beetles. Members are strictly aquatic and live almost exclusively on the water surface, where they form conspicuous aggregations called rafts. They are native to multiple biogeographic regions including the Palearctic, Nearctic, North Africa, Asia, and Australia. The genus is distinguished from the larger Dineutus by its smaller size, exposed scutellum, and more pointed elytral apices.
Stenus comma
Stenus comma is a rove beetle in the family Staphylinidae, notable for its highly specialized predatory behavior. The species employs a unique hunting mechanism using pygidial gland secretions to capture springtails (Collembola). It can eject a viscous, sticky secretion as a droplet on an extendable terminal filament to 'shoot' at prey, or apply the secretion directly during ambush. The beetle demonstrates flexible hunting strategies that adapt to different prey types and defensive capabilities. This species has a broad distribution across the Northern Hemisphere, including Europe, Asia, and North America.