Pipistrellus raceyi, also known as Racey's pipistrelle, is a bat from Madagascar, in the genus Pipistrellus. Although unidentified species of Pipistrellus had been previously reported from Madagascar since the 1990s, P. raceyi was not formally named until 2006. It is apparently most closely related to the Asian species P. endoi, P. paterculus, and P. abramus, and its ancestors probably reached Madagascar from Asia. P. raceyi has been recorded at four sites, two in the eastern and two in the western lowlands. In the east, it is found in open areas and has been found roosting in a building; in the west it occurs in dry forest. Because of uncertainties about its ecology, it is listed as "Data Deficient" on the IUCN Red List. With a forearm length of 28.0 to 31.2 mm (1.10 to 1.23 in), Pipistrellus raceyi is small to medium-sized for a species of Pipistrellus. The body is reddish above and yellow-brown below. The wings are dark and the feet are small. Males have a long penis and baculum (penis bone), which is somewhat similar to those of P. endoi, P. abramus and P. paterculus. In the skull, the rostrum (front part) is less flat than in related species and the supraorbital ridges (above the eyes) are prominent. The fourth upper premolar does not touch the upper canine and the second lower premolar is well-developed. Taxonomy Since they were first recorded in 1905, when Thomas and Schwann described the species Vespertilio matroka (currently Neoromicia matroka), the classification and status of small vespertilionid bats ("pipistrelles") from Madagascar have remained unclear. Although several species were recorded, they remained little known. A species of the genus Pipistrellus with affinities to Oriental (southeastern Asian) species was first recorded in 1995, and several later authors recorded one or more unidentified Pipistrellus species. In 2006, Paul Bates and colleagues reported on a collection of 44 Malagasy "pipistrelles" received by the Harrison Institute, which included several species new to Madagascar, as well as a single species new to science. This species, a member of Pipistrellus, was described as Pipistrellus raceyi. In a 2007 article, Steven Goodman mentioned it as part of a flurry of new bat species from Madagascar; the number of species increased from 27 in 1995 to 37 in 2007. The specific name, raceyi, honors bat researcher Paul Racey and the describers suggested the common name "Racey's pipistrelle bat". P. raceyi closely resembles