Signs of Spring: Report Your Observations!

Earthworms

Characteristics

Q. What characteristics are used to identify earthworms?

A. The easiest things to look for are color; body length; body shape (cylindrical or flattened); number of body segments; number of segments back to the clitellum on the body; and type and position of body bristles or setae.

Q. How can you tell the head of an earthworm from the tail end?

A. The head of the worm is always located on the end of the worm closest to the clitellum. Place a worm on a rough piece of paper and observe which direction it travels. Earthworms usually extend their "head" first when crawling.

Q. What is the collar or band in the middle of the earthworm?

A. The band is the clitellum. This saddle-shaped, swollen area is about 1/3 of the way back on a worm's body. The clitellum secretes mucus to form the cocoon which will hold the worm embryos.

Q. How can you determine if an earthworm is an adult?

A. The presence of the clitellum is the sign of a sexually mature worm.

Q. How big do earthworms get?

A. Lumbricus terrestris (Nightcrawler, Dew worm) is one of North America's largest. It ranges in size from 9-30 cm with a diameter of 6-10 mm. A nightcrawler nearly 30 cm long (stretched out) and weighing 11.2 g was collected in a soybean field in Ontario, Canada. The largest tropical species are up to 120 cm long. The largest in the world are some Australian forms which may reach 300 cm in length.

Q. What are earthworm casts?

A. Worm casts are the earthworm's undigested waste (worm poop). Casts are composed of organic matter mixed with soil. They are help together with "gum" produced many active bacteria and mucus.

Q. How do earthworms move?

A. Earthworms have bristles or setae in groups around or under their body. The bristles, paired in groups on each segment, can be moved in and out to grip the ground or the walls of a burrow. Worms travel through underground tunnels or move on the soil surface by using their bristles as anchors, and pushing themselves forward or backward using strong stretching and contracting muscles.

Q. Can worms crawl forward and reverse?

A. Yes. Even though worms can move both frontward and backward they tend to travel forward more.

Q. If you cut an earthworm in two, will it live?

A. The rear half will always die, and the front half may live to become another whole worm. This is called regeneration. The front part must be long enough to contain the clitellum and at least 10 segments behind the clitellum. This makes up about half the length of the worm. The new posterior segments grown will be slightly smaller in diameter than the original segments and sometimes a bit lighter in color.

Q. Do earthworms have eyes?

A. They do not have eyes but they have light- and touch-sensitive organs (receptor cells). These cells help them sense differences in light intensity and to feel vibrations in the ground.

Q. How do earthworms breathe?

A. Earthworms breathe through their skin. They need humid conditions to prevent drying out.

Q. Why are worms slimy?

A. They coat themselves in mucus, which enables dissolved oxygen to pass into their bloodstream.