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

 

 

 

 

 

Make Mine Aubergine

After two summers of drought conditions it is great to see how well the vegetable garden is doing this year. The lack rain and the elevated temperatures of last summer meant that I was lugging the watering cans from the rain barrel to the garden every other day. This year, it has been less than once a week as Mother Nature has provided precipitation in abundance. The zucchini, summer squash, tomatoes, peppers, kale, Swiss chard, green beans, carrots, and beets are all living large.

The first batch of ratatouille has already been enjoyed, a delicious blend of tomatoes, zucchini, summer squash and eggplant that is diced, tossed with olive oil and a pinch of salt, and roasted to perfection in the oven. The vegetables that provide the greatest depth of flavor in this recipe are the tomatoes and eggplant. These vegetables are found in the umami taste category (along with sweet, salty, sour, and bitter). Umami, by definition, is a Japanese word that means ‘pleasant, savory taste’. It is also known as glutamate and has been a part of the vernacular since 1985 which explains why it was not on any of the sense of taste diagrams that I saw in science class in the 70s.

Foods that contain umami such as tomatoes, eggplant, spinach, celery, and mushrooms will all have their flavor improved by just a touch of salt (or fish sauce, which is also high in glutamate) making them great choices for anyone trying to reduce their sodium intake. I recently had a Thai dinner of a spicy eggplant dish that had such an incredibly savory taste due to the combination of the eggplant and the fish sauce that I ordered it twice that week.

In fact, eggplant is one of my favorite vegetables. It is used in so many cuisines around the world. I believe that my first exposure to eggplant was through my Italian heritage in the form of Eggplant Parmigiana, a staple of every holiday meal and a prime choice when ordering from Franklin Giant Grinder on Franklin Avenue in Hartford. Those breaded sliced rounds, fried in olive oil, baked in a tomato sauce, and covered in mozzarella cheese were umami with a capital U!

Fast forward to the 1990s and the exposure to so many more dishes that use eggplant, including vegan and vegetarian recipes where it is a good substitute for meat. In the Mid-east, baba ghanoush is eggplant that is roasted whole, scooped out when cool and mixed with tahini, garlic, and a little olive oil and eaten as a dip with vegetables or pita bread. The already mentioned ratatouille is a stewed dish that comes to us originally from Nice, France, where eggplant is known as aubergine. Eggplant can be pickled or made into chutneys in India or stuffed with rice, meat, or other fillings in the Caucasus.

One thing about eggplant that separates it from most other vegetables is that it is basically inedible when raw, having a very bitter taste and an astringent quality. Early cultivars required the slices to be salted, pressed, rinsed, and drained before they could be used in a recipe but modern cultivars such as the large purple variety have less bitterness.

The three varieties that I am trying this year are the classic plump purple ‘Black Beauty’, the green skin ‘Thai Long Green’, and the white skin ‘Caspar’. It would appear that we are not the only ones finding the eggplant interesting this year.

The first pests that I noticed in July were the eggs and larvae of the False potato beetle (Leptinotarsa juncta), often confused with its cousin the Colorado potato beetle, (Leptinotarsa decemlineata). The bright orange eggs which are found standing upright on the underside of the leaf are not as tightly packed together as the eggs of the squash bug generally are. It wasn’t until I looked at an enlarged view of the below image that I noticed that I had actually captured a larva emerging from an egg!

The pale larvae will feed on the foliage of most Solanaceous plants for 21 days as they go through 4 instar stages and then drop to the soil to pupate.

After 10 to 15 days the adult beetle will emerge and lay eggs. There are usually two generations a summer in Connecticut.

Then there were the larvae of the Clavate tortoise beetle (Plagiometriona clavate), awesome masters of disguise, who use their own frass (poop) as a camouflage. The rear abdominal segment of the larva has a special fecal fork that allows the attachment of the dried fecal matter and holds it over the larva, hiding it effectively. Even if the frass is pulled back it will pull it over again.

These small, green larvae with their flattened bodies and fringe of white spikes did a bit of damage to the eggplant leaves, leaving them quite pockmarked.

A few more visitors are not as Solanaceous host-specific as the False potato beetle and the Clavate tortoise beetle. The 14-spotted lady beetle (Propyleae quatuordecimpuctata) has been in North America since it came to Ontario by way of Europe in the 60s. It can out-consume the native North American lady beetle species, eating insect pests such as aphids, mites, and scale, landing it on the Invasive Species Compendium list.  Every garden needs pollinators and the bees love the big purple blooms of the eggplant.

This grasshopper nymph posed on an eggplant leaf, casting a very artful shadow. Grasshoppers are not picky eaters and can be found on every plant in the garden although squash and tomatoes are their least favorite. This one may have just been taking advantage of a bit of August sunshine. Can’t say that I blame it!

Susan Pelton