Head and body length is 160-90mm with a vestigial tail. Adult weights vary from 80-280 gms. Two subspecies exist with slightly different coloration. Base color is black with chestnut brown markings in H. semispinosus and whitish markings in H. nigriceps. The stripes of H. semispinosus are more distinct of the two, but both have a prominent crest of spines at the nape of the neck. The underparts of H. semispinosus are covered with chestnut brown rather spiny hairs.

H. semispinosus is primarily terrestrial, though it is capable of climbing, and may be active any time of day. During winter months, the animal can achieve a state of torpor, the body temperature becoming 1°C less than the ambient temperature. It inhabits rainforests and brushland and has recently extended its range to cultivated fields. H. semispinosus' diet consist mainly of earthworms.

Sexual maturity is achieved at only five months for H. semispinosus females and litter size averages 6.6 young. Babies are born from November through March, after gestation periods of 55-63 days.

There are three sounds produced by Tenrec, which are audible to humans. A "putt putt", a crunching sound during agonistic behavior and a vibration known as stridulation emanating from specialized quills in the middorsal region. This last sound appears to be most important in helping mother and young locate one another.

Hemicentetes semispinosus is found in the eastern humid forest and central highlands of E Madagascar.