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Bipalium kewense, also known as the shovel-headed garden worm, is a species of large predatory land planarian with a cosmopolitan distribution. It is sometimes referred to as a "hammerhead flatworm" due to its half-moon-shaped head, but this name is also used to refer to other species in the subfamily Bipaliinae.
The anterior end ("head") is expanded in a transversal semilunate shape and the body is the narrowest just behind the head, in a region called "neck". The dorsal color is light-brown with five black to grey longitudinal stripes that begin at the neck. The median and marginal stripes are narrow and black, very distinctly marked. The lateral stripes (between the median and marginal stripes) are usually grey, broad and with diffuse margins. The neck is usually marked by an incomplete black collar formed by the union of the marginal and lateral stripes, this being one of the main characteristics to distinguish it from similar species. The head usually has a darker color than the background color of the dorsum and lacks stripes. The ventral side has a light ochre color externally and whitish over the creeping sole, which is externally lined by two diffuse grey-violet longitudinal lines.
The species was first found in 1878 in the area of the Kew Gardens in the London Borough of Richmond upon Thames, United Kingdom, hence the name kewense.
Asexual fragmentation is the primary means of reproduction in B. kewense in temperate regions. Long specimens usually release body fragments at the posterior end by transverse fission. The fragments are motile and regenerate the head plate and pharynx in a few weeks. Such a reproduction strategy is considered one reason for the successful colonization of this and other species of Bipalium.
Although there is little evidence of sexual reproduction in these planarians, there have been several reported cases of egg capsules being discovered. The egg capsules discovered had several of the same characteristics of those of B. adventitium, including coloration and incubation period. The most recent egg capsule discovered hatched offspring that did not bear a complete resemblance to adults and were considerably larger in size to that of B. adventitum offspring.
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