Chemical Defenses of Ants and Their Cousins

This week is Insect Week as declared by the Royal Entomological Society, a biennial event to celebrate these little critters and encourage us to learn a bit more about them. So, I thought I'd contribute by sharing some knowledge about the chemical defenses of insects in the Order Hymenoptera, which includes ants, bees, wasps, sawflies, and hornets.

The name Hymenoptera stems from the insects in this order that can fly because they have two pairs of membranous (thin + transparent) wings, where each pair of hind + fore wings are joined together with a series of hooks. "Hymen" is a Greek word that means "membrane." It's true that a few Hymenoptera insects like some of the ants are wingless, but most in the order can fly. Hymenoptera insects also have a long organ that some use to lay eggs, whereas in others, it functions as a saw, piercer or stinger. Their life cycles undergo metamorphosis with four stages of growth from egg, larvae, pupa to adult.

This large order of insects are some of the most fascinating in the world. In popular culture, they have also inspired a number of comic-book superheroes including Ant-man, Wasp, Yellowjacket, Bumblebee and The Green Hornet.

Chemistry of Hymenoptera Defenses

A few years ago, I was invited to participate in a Natural History Show in Toronto where I could only showcase science + art works related to zoology, botany, ecology, anatomy, fossils or gem stones. This challenged me to "think outside the box" as my designs at that time were mostly related to the chemistry of materials, food + drink, or emotions rather than about the biology of animals or plants.

How could I create a design in a different field of study while also staying true to my style of using molecule diagrams for my designs?

So, I read and I researched,
researched and I read
all that I could
about this and that.

I came up with five original art works related to the chemistry of plants, insects, and fungi. One of them was about the Chemical Defenses of Hymenoptera Insects.

ANTS

Ants live in highly organized colonies all over the world, except Antarctica. Within their hierarchical colonies, there are many different roles: workers, soldiers, drones and a queen. As a defense mechanism, some species of ants bite or sting and deposit venom.

Formicine ant venom contains a chemical called formic acid
Fire ant venom contains piperidines, the same class of chemical found in black pepper
Bullet ant venom contains ponera toxin, a peptide that affects the nervous system

BEES

Bees, our sweet buzzing honey-producing pollinators are valuable contributors to all ecosystems. Bees can either be solitary or live in hives with organized colonies of a queen and many workers. They are well-known for stinging as a defense mechanism and their acidic venom contains the toxic peptide melittin, histamine that makes skin feel itchy and isoamyl acetate, an alarm pheromone that acts as a distress signal. Coincidentally, this pheromone smells like bananas.

SAWFLY

Sawflies are herbivores with many predators. They have a lengthy larval stage during their lifecycle and their young larvae defend themselves by secreting a chemical called sinalbin whenever predators are present.

WASP

Wasps can be solitary or live in nests with colonies of a queen and many workers. Most wasps are parasitic because they lay eggs in other wasps' nests. The solitary wasps are parasitoid in that they lay eggs inside or on other insects (while those insects are themselves dormant as eggs or pupa); then wasp larvae feed on the host until adulthood, at which point the host dies. As a defense mechanism, wasps release an alarm pheromone in their sting called 2-pentanol.

HORNET

Hornets are a type of wasp that are mostly found in the Northern hemisphere of the world. Their sting contains large amounts of a chemical called acetylcholine, as well as alarm pheromones such as 2-pentanol, 3-methyl-1-butanol, 1-methylbutyl 3-methylbutanoate or 2-methyl-3-butene-2-ol.

I hope you learned a bit more about these interesting insects in the Hynenoptera order. If you're curious about anything else, just ask in the comments below.