Crithidia
Crithidia is a genus of tiny, single‑celled parasites that belong to a group called trypanosomes within Euglenozoa. They mainly parasitize insects and spread between hosts as cysts in infected insects’ feces.
Inside the insect gut, Crithidia grows and interacts with the lining of the intestine using its whip‑like tail (flagellum). The parasites are not very picky about their hosts and a single Crithidia species can infect many different invertebrates.
During its life cycle, Crithidia can take several forms—amastigote, promastigote, and epimastigote—with the epimastigote stage being especially typical. This stage is often referred to as crithidial in related parasites. The name Crithidia comes from the Greek word krithídion, meaning a small grain of barley.
Impact on pollinators: Crithidia may contribute to declines in wild bumble bee populations. Infected bees may lose the ability to tell which flowers have nectar and may visit nectar-poor flowers by mistake, wasting energy and possibly starving.
Commercial bumble bees used for greenhouse pollination can carry Crithidia, while wild bees usually do not. The parasite can spread from greenhouse bees to wild populations, for example through vents. A simple mesh screen can help prevent this spread.
Examples of Crithidia species include Crithidia luciliae, Crithidia fasciculata, Crithidia mellificae, and Crithidia bombi.
This page was last edited on 3 February 2026, at 02:36 (CET).