Forest Litter, Critters to See

Last week, we started to look at the forest floor and the litter covering it, composed of leaves, dead wood, animal carcasses and other organic waste.  A complex community of organisms thrives in this habitat, working to return the nutrients from the litter back to the soil to be used again as food for green plants.  The first layer of this community consists of decomposers.  This week, we investigate several other layers.

Many species can be spotted among the litter, but observing them takes patience.  Carefully sorting through leaf litter is a skill learned through practice.  Overturning decomposing logs and probing through rotting bark will yield great results if done slowly and without great disturbance to the animals present.  Animals can be observed with your eyes, a hand lens, or a microscope.

Using your eyes, there are several species that like moist conditions and are easily found under decaying logs.  Many are very active after an autumn rain.  Some of the more abundant species are:

• Slugs are a type of mollusk with a soft, slimy body that leave a slime trail wherever they go on their nighttime feeding excursions.  They eat decomposing leaf litter and animal remains.

• Snails, another mollusk, are covered with a hard shell for protection from predators and to help retain moisture.  They also eat decomposing vegetation and animal remains.

• Isopods, also known as wood lice or pillbugs, must have moist conditions because they breathe using gills.  Often found under logs after a rainfall, they move quickly using their 14 pairs of legs.  There are several hundred species found in field and forest habitats.

• Millipedes are segmented and covered by an exoskeleton. Feeding on litter and animal remains, they can be found in any slightly wet area.  Millipedes protect themselves when threatened by rolling up into a tight ball.   

Several species can be found in any litter conditions.  Many are predators, hunting and feeding on other animals.  Some often found in our forests include:

• Centipedes may look like millipedes, but are predators, eating many smaller insects.  The first pair of legs by their head are modified into sharp, poisonous claws used to capture and stun their prey.

• Spiders have four pairs of legs, no antenna, simple eyes, and powerful jaws with poison glands.  The injected toxin liquifies the soft tissues inside the victim’s body, allowing the spider to suck them out.  Many species, including the popular wolf spider, are ground dwelling, digging burrows and hunting by night.

• Harvestmen, also known as daddy long legs, are similar to spiders.  They have four pairs of very long legs.  When disturbed, they will wave the front two pair around to ward off another predator.  They feed on small insects and decaying plants and tend to hunt in groups, mostly at night.

Next we will investigate what a hand lens can reveal about some of the most numerous inhabitants.