Animals

Hymenopterans - Ants, Bees, Wasps

by Marcia Malory

Ants, bees, wasps and sawflies make up the order Hymenoptera.

Many hymenopterans have high levels of social organization (are eusocial). They may live in large colonies where division of labor occurs.

Division of labor means that different individuals perform specialized tasks.

The name Hymenoptera means "membranous wing".

Honey bee

Hymenopterans usually have two pairs of wings. The front wing is smaller than the back wing. Small hooks join the front and back wings together.

Their diet varies.

Some are carnivores; they eat other animals. Others are herbivores; they eat plants.

Some hymenopterans have an elongated mouthpart, known as a proboscis, which they use to suck nectar from flowers. Hymenopterans are important agents of pollination.

The egg-laying organ, or ovipositor, is sometimes modified to be a stinger that delivers venom.

Hymenopterans undergo complete metamorphosis. Some larvae look like caterpillars (butterfly or insect larvae) and others look like maggots (fly larvae).

The larvae of some hymenopterans are parasites.

Sex

The sex of a hymenopteran depends upon the amount of chromosomes it has.

Females come from fertilized eggs and have two sets of chromosomes, from a mother and a father.

Males come from unfertilized eggs and have one set of chromosomes, from a mother.

This arrangement is known as haplodiploidy.

Parthenogenesis is the term that describes reproduction in which only the female provides a genetic contribution.

Haplodiploidy creates a situation in which females are more closely related to their sisters than to their daughters.

On average, a female is likely to be 75% similar, genetically, to her sisters. This is because there is a 50% chance that she and her sisters will get the same genes from their mother, but a 100% chance that she and her sisters will obtain the same genes from their father.

However, a female is likely to be only 50% similar, on average, to her daughters, because she will give only half her genes to her daughter.

This means that, from an evolutionary standpoint, it is more advantageous for a female to help her mother produce more daughters (her sisters) than to care for daughters of her own.

Some entomologists think that this has encouraged hymenopterans to cooperate and ultimately, to developing complex social organizations.

Colonies of hymenopterans often consist of queens (reproducing females), drones (males) and workers (females that do not reproduce). The workers ensure the survival of their own genes by helping the colony to survive.

Army ants eating a grasshopper, photo by Karmesinkoenig

Army Ant

Army ants live in large colonies that are constantly moving.

They are predatory and engage in raids in which they attack a variety of animals, including snakes, lizards and small mammals and birds.

Gall Wasp

The female gall wasp lays her eggs on the stems, buds or leaves of a tree, often an oak tree.

When the larvae hatch, they secrete substances that irritate the tree. The tree forms galls - abnormal growths of tissue - around the areas that are irritated.

The larvae grow inside the galls. They become pupae will still inside the galls, and then eventually break out when they become adults.