Defense Strategies of Some Insects

Female Io moth has prominent eyespots to scare birds and other predators

Many insects never make it to adulthood to complete their life cycles because in the grand scheme of things, they are low on the food chain. There are no lack of creatures that rely upon insects for food, both for themselves, and perhaps their young as well.

Rose hook tip moth is hard to see resting on leaf in the woods

But insects are not necessarily limpid little defenseless victims of a more sophisticated life form. They have strategies to overcome the odds of becoming dinner for something else. Some use camouflage, others are cryptic in manner and color while some have mastered the technique of veiling themselves with material. Others simply hang out  in plain sight, protected by urticating spines or irritating hairs.

Clavate tortoise beetle larva carries excrement and debris over its back by means of a forked appendage on the rear of its abdomen

The wavy- lined heterocampa feeds and rests along leaf edges and manages to blend in to avoid many predators. Other caterpillars are armed with urticating spines or irritating hairs that release toxins when touched. Lesson learned after contact with these guys.

a wavy- lined heterocampa caterpillar is feeding along the lower right of the leaf edge

Camouflage loopers are small caterpillars that are found on composites. They take petals from the plant’s flowers and “glue“ them on their body. They blend in so well that the only evidence of their presence will be that the flowers seems to be deformed. Other loopers are twig mimics and hide in plain sight.

A camouflage looper (center, top) is aptly named, attaching pieces of flower petals to its body to hide on goldenrod flowers

Io moth caterpillars are covered with spines that give a painful sting when touched

Some insects form leaf shelters which they hide inside to avoid discovery. Stink bugs often use abandoned shelters of other insects, while the spicebush swallowtail caterpillar makes its own by folding a leaf lengthwise.

The caterpillar of the spicebush swallowtail not only has huge eye spots, but it hides inside a folded leaf on its host plant

 

There are insects that have eye spots that may help scare off predators like birds and small animals. The eyed click beetle, female Io moth and the spicebush swallowtail caterpillar are a few examples of insects that use eyespots as a threat defense. Some prominent caterpillars, like the white furcula and the black-etched prominent have modified anal prolegs that are more like tails. When disturbed, they flail these around and may scare off parasitic insects and other threats. The small filament bearer looper has a pair of pale-tipped tentacles on its dorsum it can flail about when alarmed.

Black- etched prominent caterpillar flailing modified anal prolegs

Eyed click beetle

Thyridopteryx ephemeraeformis bagworms spin a silk bag to which they attach host plant leaf material-whether pieces of leaves or needles. They remain safely inside until night comes, which is when they feed. Hard to detect when host plant material is fresh, during the winter look for the dangling brown bags. Remove as you see fit.

Pieces of oak leaves were stuck on the silken bag of the Thyridopteryx ephemeraeformis eastern bagworm.

Walking sticks are very cryptic in coloring, often blending in with leaf veins of host plants. Unless they move, they are very difficult to discover. Some loopers have coloring and markings that are very similar to their host plants, one being the oak besma caterpillar.

Walking stick blends in with the leaf veins of native filbert

Viceroy and red- spotted purple butterfly early instar caterpillars eat leaf tips first and then rest on the exposed midrib where they are hard to see. Later instars hide in plain sight on upper sides of leaves, avoiding detection by resembling bird droppings and remaining stationary by day.

Viceroy caterpillar on mid rib of eaten leaf tip

 

Some insect larvae feed within plants where they escape predation. Gall- forming insects, leaf miners, and borers are some examples of internal feeders. The female leaf rolling (or thief) weevil chews along oak leaves and rolls the flap tightly. It remains attached to the leaf, so the piece stays alive as the weevil larva feeds safely from inside this structure called a nidus.

Grape tube maker galls on wild grape

 

There are many other ways that insects can survive predation including cryptic coloring, hiding in leaf litter, and simply dropping from plants when alarmed. They may be small, but they are well equipped for their struggle to survive on planet earth.

Oak besma looper on right, oak twig of host plant on left

 

Pamm Cooper