Bombyx mori 300 to about 900 m (1,000 to 3,000 ft) long. The fibers are very fine and lustrous, about 10 μm (0.0004 in) in diameter. About 2,000 to 3,000 cocoons are required to make a pound of silk (0.4 kg). At least 70 million pounds of raw silk are produced each year, requiring nearly 10 billion cocoons. Due to its small size and ease of culture, the silkworm has become a model organism in the study of lepidopteran and arthropod biology. Fundamental findings on pheromones, hormones, brain structures, and physiology have been made with the silkworm. One example of this was
Maru Maru Mori Mori! Maru Maru Mori Mori! On 4 April 2011, it was announced that the theme song of the Fuji Television television drama "Marumo no Okite" will be sung by actress Mana Ashida and Fuku Suzuki, both of whom are also starring in the television drama. They formed a temporary group called Kaoru to Tomoki, Tamani Mook, and the song that they will be singing is entitled "Maru Maru Mori Mori!" This singles album debuted on the Oricon charts at the third position with sales of around 35 thousand albums in the first week. This makes the group the youngest group ever