A. ANT LIONS: THE HAIRY PREDATOR FROM DOWN UNDER
If ant lions were the size of humans, we'd live in almost constant fear of falling into their traps, being drained of blood by their large, hypodermic-like jaws, and discarded like fast food trash. Sound like a horror movie? Life as an insect can read like science fiction. The drama of the voracious, bizarre-bodied, predatory ant lion and its death pit will surely captivate your students.
Lucky for educators, where there is sand there are ant lions! These hairy, backward-moving creatures--known to many as doodlebugs--are fascinating insects to watch, easy to find every month of the year, simple to catch, and can be kept indoors for several weeks with minimal effort. A combination of indoor and outdoor observation is recommended.
Getting students involved with ant lions at this point in the curriculum should help solidify concepts that were introduced in the previous chapter on sand. The ant lion also makes a good contrast to the wolf spider, another digging and ambushing predator. Ant lions are very accessible to your students. They are very common all over Florida and are often found near buildings. A project with these insects will give your students a little area of specialized knowledge about a very interesting animal that they can share with friends, parents, and relatives.
Ant lions are the larvae of a group of insects called Neuroptera, which includes lacewings and dobsonflies. Active day and night, larval ant lions are usually light gray or brown, have fat, hairy, segmented bodies, short legs, and long curved jaws on tiny heads. Some species are very small and others can be as big as your fingernail! They move backward most of the time and tickle when they "doodle" in your hand. Their stiff hairs point forward, which helps to anchor the ant lion in the sand, even when struggling with prey. Ant lions are not harmful to people and will not pinch you with their jaws. Typically, they "play dead" when held.
The adult ant lion resembles a damselfly, but is a weak flyer. Usually nocturnal, adult ant lions are rarely seen. You might encounter one resting on a vertical twig or grass stem or see one near a light at night.
The Drama of the Pit
After mating, the female ant lion lays many eggs in soft dry sand. After the eggs hatch, the larvae will build pits in the sand under undisturbed cover, such as palmetto leaves, dead leaves, roof eaves, and even in tree hollows. Because most prey are too fast for the ant lions to catch, building pits is a very energy efficient way for it to get food. Although the meal is usually an ant, ant lions will eat other small insects that fall into their pits. Because beetles are slick and hard, ant lions often have trouble capturing them.
Ant lions build their traps by spiraling around and around from the top of the pit at the surface of the sand to the deep point in the funnel. The ant lion then sits at the bottom with its body covered by a thin layer of sand and waits, with open jaws, for its prey to slip in. To be effective, the trap must be kept neat. If small objects, such as pebbles or bits of plant material fall into the pit, the ant lion will try to clear them away. After a rainy or windy day, the ant lion often needs to reshape its pit. If it doesn't catch enough prey in its trap, the ant lion often abandons it and moves to another location.
The ant lion's pit is steep and slippery. The ant lion uses fine grains of sand, which hold together to form a steep slope and are likely to slide when touched. When an insect falls into the pit and struggles to escape, the ant lion quickly responds by flicking sand grains. These bombard the prey and cause more sand to slide to the bottom of the pit, sweeping the prey down with it. The open, ready jaws snap shut and the ant lion slowly pulls the struggling prey underground to secure its capture. Digestive juices and a toxin are then injected into the prey's body, liquefying everything but the exoskeleton. After sucking the liquid meal up through its jaws, the ant lion tosses the exoskeleton from the pit.
Ant lions have predators, too. Their pits alert birds to a potential snack! Parasitic wasps and flies often lay eggs on ant lions. Once the eggs of the parasitic wasp hatch, their larvae consume the ant lion.
When the ant lion larva reaches full size, it pupates within a small ball of sand and silk just under the surface at the bottom of its pit. The pupa is very well camouflaged and difficult to find. When ant lions die or pupate, their pits become messy or disappear.
Hunting is not the pits
Some ant lion species do not build pits, but are easily recognized by the unique doodle-like trail they leave in the sand as they actively hunt for prey. The hunting ant lion can usually be found at one end of the trail. Pit making ant lions also doodle briefly just before making their pits or moving to another location. Just how do they find ants if they're hunting backwards in the sand?
Search dry, undisturbed sand for funnel-like pits. Your students will be very good at this! Particularly good sites will often have many pits clustered together. An active pit will be neat and well formed. If you look carefully, you may even be able to see the ant lion's jaws at the bottom of the pit, open in anticipation. With a cup or spoon, carefully scoop out a thin layer of sand at the base of pit or at the end of trail. Search the sand carefully for the ant lion. They are usually very well camouflaged and are especially difficult to see if they "play dead."
Once you have a captive ant lion, make sure to provide it daily with ants or other insects and a drop of water about every three days. A hunter ant lion will need room to make its trail, but a pitmaker will be content in a cup. You may want to line the top of your container with petroleum jelly to keep the ants from getting out. Make sure to put your containers of ant lions in a low traffic area so they are less likely to get bumped.
|Unit II. SAND-DWELLING ANIMALS
A. Ant Lions: II.A.1
B. Scrub Burrowing Wolf Spiders: II.B.1
C. Ants: II.C.1
D. Glossary E. Questions for Student Evaluation