Beneficial insects in the garden: #32 Ant lion (Myrmeleon sp.)

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	FIGURE 1. Ant Lion larvae (Myrmeleon sp.) are sit-and-wait predators that construct sand pits with the shape of an inverted cone or funnel. Sand pits are often very abundant under sheltered areas with sandy soil such as under roof overhangs and raised foundations as well as in the shade of large trees.


	FIGURE 2. While larvae are well-known for feeding on ants (shown near the bottom of a pit being pulled under by an ant lion larva), older, larger size larvae are quite capable of capturing and killing a variety of other insects that enter their sand traps.


	FIGURE 3. Adult Ant Lions resemble dragonflies or damselflies and are not commonly encountered in the wild because they are active in the evening primarily.


	FIGURE 4. Myrmeleon larva are fearsome appearing creatures. The head bears a very impressive and sizable pair of sickle-like jaws (known as mandibles) that are armed with numerous sharp, hollow projections. (Photo of preserved specimen in insect collection maintained at Galveston County Extension Office.)

Quick Facts
Common Name:	Ant Lion
Other Common Names:	Ant-lion, antlion & doodlebug
Size:	Fully developed, well nourished larvae can grow to ½ inch (1.2 cm) in length. Adult stage 1½ inch (4 cm) long
Genus / Species:	Myrmeleon sp.
Type of Beneficial:	Insect predator
Type of Metamorphosis:	Immature stages appear different from the adult stage (i.e., complete metamorphosis)
Beneficial Stage(s):	Immature stages are voracious feeders. Adult stage feeds on nectar and pollen
Prey:	Larvae feed primarily on ants but will also feed on other small insects that enter into pit in addition to small spiders
Occurrence:	Occur in limited areas across the Galveston-Houston region; more common in areas of Texas with sandy soils
Mounted Specimen?	Yes (mounted specimen for viewing available in insect collection at County Extension Office)
Additional Notes:	2,000 species of ant lions are distributed throughout the world but not all species build sand traps

Have you ever heard of a "doodlebug"? It is actually the larvae of an insect commonly known as an Ant Lion (also spelled as “ant-lion” and “antlion”). Ant Lions are a group of insects in the Order Neuroptera. Within this order, they are further classified into Family Myrmeleontidae, which is of Greek origin from myrmex, meaning "ant", and leon, meaning "lion".

Technically speaking, the term Ant Lion applies to the immature or larval stages of the members of this family. Ant Lion larvae are predatory while the adult stage feeds on nectar and pollen. Larvae are voracious predator of ants and other small insects that become entrapped in the conical pits constructed by Ant Lion larvae.

Ant Lion larvae (Myrmeleon sp.) are also known as doodlebugs. This nickname is apparently in reference to the randomly winding and spiraling trails that young larvae make in the sand while seeking a suitable location to construct its larval home. The trails look like someone has been idly doodling in the sand! The larvae’s home in the sand is also a novel insect trap known as a pit.

Pits have the shape of an inverted cone. The pits are found in dry places that are sheltered from exposure to high winds and intense sunlight. Pits are oftentimes constructed under the shelter of farm buildings, under houses that are on piers, etc. These pits are usually 1½ to 2 inches in diameter and about the same depth. (Some Ant Lion species also hide under bits of debris or wood and attack passing insects.)

The Ant Lion larva waits at the bottom of its pit for an ant or other insect to slip on the loose sand and fall in. The unsuspecting prey falls to the center of the pit and into the waiting jaws of the Ant Lion larva, mealtime is underway! Prey will oftentimes attempt to scramble up the steeply inclined walls of the pit. Such desperate efforts to escape its circumstance are typically to no avail. An Ant Lion larva quickly thwarts such escape attempts by rapidly flicking showers of loose sand, which further destabilizes the wall of a pit and thereby draws the prey downwards.

The larva is a fearsome-appearing creature and its head bears a very impressive and sizable pair of sicklelike jaws (known as mandibles) that are armed with numerous sharp, hollow projections. The mandibles have a piercing-sucking function. After seizing its prey, the larva paralyzes it with poison injected at the first bite. Additional digestive enzymes are injected to breakdown the internal tissues of its prey and the larva then sucks out its vital juices. After consuming the liquefied contents of the prey’s body, an Ant Lion larva rather unceremoniously flicks the lifeless, drained carcass out of the pit. Thereafter, the larva repairs the pit once again for the next unsuspecting victim.

Ant Lion larvae eventually pupate in the soil. Adults resemble dragonflies and damselflies except the Ant Lion folds its wings back in a tent-like fashion while resting. Adults are rarely encountered in the wild because they are primarily active in the evening. During the day, Ant Lions rest and are usually motionless and quite well-camouflaged by its transparent wings and brownish body. Also in contrast to dragonflies and damselflies, the antennae of ant-lion adults are quite prominent and club-shaped at the end.

The larval stages are beneficial to man because of their diet. Larvae are well-known for feeding on ants. Moreover, as Ant Lion larvae increase in size, they become quite capable of capturing and killing a variety of other insects that enter their sand traps. One entomologist reported that he maintained Ant Lion larvae for laboratory study by feeding them “.... a diet of one house cricket nymph per day.” Ant Lion larvae have also been reported to feed on the dreaded red imported fire ant. Ant Lion larvae also feed on small spiders.

The ability to subdue prey much larger than itself is due, in part, to its entire body being covered in stiff bristles that helps anchor it to the sand while countering the fleeing efforts of its prey. In fact, the bristles are forward-pointing, which provides additional leverage to firmly anchor its body against the vigorous struggles of its prey.

Ant Lion larvae are truly one of the most fascinating of insect predators. They do occur in the Galveston-Houston region but not abundantly but we do have specimens in our insect collection. Ant Lions are more prevalent in areas with sandier soils than in our region. Consequently, Ant Loins are more frequently encountered in the Piney Woods (East Texas), the Hill Country (central Texas) and the Texas Central Gulf Coast region.

Interesting Report on Dynamics of Sand Pits

If you are really interested in learning more about sand pits, the following excerpt is taken from a paper entitled “Adaptive short-term changes in pit design by antlion larvae (Myrmeleon sp.) in response to different prey conditions”.

Features of pit architecture, such as diameter, slope, and depth, influence success in prey capture (WILSON 1974; GRIFFITHS 1980, 1986). A successful capture (i.e., prey consumption) depends on both efficiency in trapping prey (an encounter) and on minimizing the probability that the prey escapes (retention). These two components should have selective consequences for the design of the trap. For example, augmenting the diameter of the trap increases the probability of encounter, while a steeper slope and a greater depth increase the probability of prey retention (GRIFFITHS 1980, 1986).

Excerpt from paper by S. LOMASCOLO and A.G. FARJI-BRENER of Argentina. Click on the following link for the full version:

http://ejour-fup.cilea.it/index.php/eee/article/viewFile/920/866

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