Insects, Spiders, Centipedes, Millipedes

A female Eastern Ringtail Dragonfly. Males of this genus have a slightly clubbed tail, where the females have a straighter, pointed tail.

Ken Larsen

Bugging out!

Let's talk about bugs, also called insects! Though usually pretty small, insects fill important niches. Niches are roles and jobs that plants and animals fill in their habitats and ecosystems. Several of these essential roles in Great Falls Park’s ecosystem for insects are:

• They’re a key source of food for many kinds of animals.
• Some insects pollinate plants.
• Other insects decompose dead plants and animals, restarting the nutrient cycle.

Nature simply couldn’t function as we know it without insects.

To bug or not to bug?

Scientists have developed a system to group organisms based on their shared traits. What traits define an insect? They have six jointed legs, three body sections (head, thorax, abdomen), and a hard outer shell, called an exoskeleton. Most insects also have one or two pairs of wings.

Insects are the largest group of animals, both in number of species identified and total individuals. Scientists have identified about 1 million different insect species so far. That is three quarters of all known animals! Scientists estimate there may be about 5 to 10 million insect species across the planet. Why such a big population? Insects tend to lay a lot of eggs at a time, because so many animals eat insects through all life stages.

Within Great Falls Park, there are an estimated 300 different species of insects! From spring through fall, you’re likely to find them along the trails, at flowers, drinking from puddles or mud, living in streams and ponds, and many other places here. You won’t see many insects during the winter, though—although they’re still around, they are underground or in other shelters. Sometimes even as eggs waiting to hatch as soon as the weather gets warmer.

 

Learn more about butterflies and moths in Great Falls Park!

 

But wait, there’s more!

Spiders—There are dozens of spider species living in Great Falls. These eight-legged predators are members of order Araneae, part of class Arachnia. This also includes scorpions, ticks, and mites. They have many ways to catch prey: some ambush insects at flowers, others hunt on the forest floor, while still others construct sticky webs to snare flying insects, and occasionally hikers!

All spiders spin silk for various uses. Orb-weavers spin the sticky webs. Jumping spiders and wolf spiders take a different approach, using silk to lay a safety line as they hunt. Spiders also weave silken egg sacs to cradle their cluster of eggs until they hatch into itsy-bitsy spiders. In some species, baby spiders create strands of silk that act as parachutes, wafting them away on the breeze to find a new home.

Legs for Days

If you’re really interested in invertebrate legs, you’re in luck. Great Falls is also home to several kinds of centipedes and millipedes.

Centipedes, members of class Chilopoda, have long segmented bodies with a single pair of legs per segment. Despite their name, no species of centipede has exactly 100 legs. In fact, they always have an odd number of pairs of legs. Scientists who study centipedes say this is because the arthropods develop body segments in pairs, two pairs of legs at a time. Their venom-bearing pincers are actually a modified pair of legs. How many legs a centipede actually has varies by species—from 15 to 191 pairs, not counting the pincers.

Centipedes are usually found in moist leaf litter or under logs and stones. They are fierce predators despite their tiny size.

Millipedes have two pairs of legs per body segment. While most species don’t have literally 1,000 legs, scientists discovered a species in Australia that has over 1,300 legs! The discovery was in 2020 and they named the species Eumillipes persephone.

Millipedes eat detritus (decaying leaves, fungus, etc.). This means they are often found roaming the forest floor or exploring rotting logs. Their long, segmented bodies are solidly armored. When they are attacked they curl into a tight coil to protect their legs and underside. If you find a coiled-up millipede, be kind and leave it to recover in peace.