Androdioecy
Guides
Eulimnadia
clam shrimp
Eulimnadia is a genus of small freshwater branchiopods commonly known as clam shrimp. The genus is notable for its rare androdioecious mating system, where populations consist of males and hermaphrodites but lack pure females. This reproductive strategy has persisted for an estimated 24–180 million years across multiple speciation events, making it one of the most stable examples of androdioecy known in animals. Species are distinguished primarily by the morphology of their resting eggs (cysts), which show distinctive sculpturing patterns. The genus contains approximately 13–25 described species with a cosmopolitan distribution across every continent except Antarctica.
Icerya
Cushion Scale Insects
Icerya is a genus of scale insects in the family Monophlebidae, notable for containing some of the few hermaphroditic insects known to science. The genus includes approximately 50 described species distributed worldwide, with several species being significant agricultural pests. The most economically important species is Icerya purchasi (cottony cushion scale), native to Australia but now cosmopolitan in distribution, which has caused severe damage to citrus crops globally. Several Icerya species exhibit androdioecy—a rare mating system where hermaphrodites and males coexist—with hermaphrodites possessing ovotestes and reproducing primarily through self-fertilization. This reproductive strategy, combined with the sessile nature of adult females, contributes to their invasive potential. The genus is named after physician-naturalist Dr. Edmond Icery of British Mauritius.
Icerya purchasi
cottony cushion scale, fluted scale, cochinilla australiana
Icerya purchasi is a scale insect native to Australia that has become a globally distributed pest of citrus and ornamental plants. The species is notable for its distinctive reproductive system: most individuals are hermaphrodites capable of self-fertilization, with rare males enabling occasional outbreeding. Adult females are sessile and produce large white fluted egg sacs that can exceed twice the body length. The species achieved historical significance as the target of one of the first successful biological control programs, using the vedalia beetle (Novius cardinalis) in California in 1888–1889.
Lepadidae
Goose Barnacles
A family of pedunculate (stalked) barnacles established by Charles Darwin in 1852, commonly known as goose barnacles. Comprises approximately five genera and over 20 described species. Members are exclusively marine, with worldwide distribution in warm temperate and tropical seas. The family includes the well-known genus Lepas (goose barnacles) and Conchoderma (whale barnacles).
Spinicaudata
clam shrimp
Spinicaudata is an infraorder of small, bivalved branchiopod crustaceans commonly known as clam shrimp. They inhabit temporary freshwater pools, saline lakes, and rock holes (gnammas) across arid and semi-arid regions worldwide. The group is characterized by a laterally compressed body enclosed within a hinged, clam-like carapace. Many species produce drought-resistant resting eggs that persist in dry sediments until favorable conditions return. Reproductive modes vary, with some lineages exhibiting androdioecy (hermaphrodites with occasional males) and others gonochorism (separate sexes with ~1:1 ratios).