Getting Started

Getting Started

In order to improve your skills as an entomologist, you will be examining two orders of insects very closely in this project. These orders are Hymenoptera and Diptera.


Hymenoptera

Bees, wasps, ants and sawflies all belong to the order Hymenoptera. They have combinations of characteristics that other insects do not have, but some flies, beetles and other insects mimic Hymenoptera in appearance and are often mistaken for them. In this exercise you will take a closer look at some body characteristics of Hymenoptera that are useful in separating them from other insects.

Hymenoptera are typically winged, but some are wingless. Winged Hymenoptera have two pairs of membranous wings with the hind wings smaller than the front wings. The wings are not hairy or scaly. In most Hymenoptera the abdomen is pinched or narrowed between the abdomen and thorax, but in some Hymenoptera, such as sawflies, the abdomen and thorax are broadly joined. (See the drawings) The condition of having the body narrowed between the abdomen and thorax is called "wasp-waisted." All wingless Hymenoptera are wasp-waisted. Many have a stinger at the end of the abdomen.

All Hymenoptera havemouthparts with chewing jaws, or mandibles. Part of the mouthparts, especially among bees, may be adapted into a proboscis for sucking nectar. The compound eyes are usually large and the antennae are long.

Some of the groups of Hymenoptera are often confused with each other. Sawflies differ from the others in not being waspwaisted. Ants differ from other Hymenoptera by having one or two bumps, called nodes, on their wasp waists. Ants may be winged or wingless. Leg characteristics are helpful in separating wasps from bees. The five basic leg segments beginning with the segment attached to the body are coxa, trochanter, femur, tibia and tarsus. The tarsus is divided into subsegments, and in most insects the subsegments are more or less the same size. In wasps and bees the first subsegment of the tarsus is much larger than the others and is called the metatarsus. The metatarsus of bees is very large and flat. In wasps the metatarsus is round in cross-section.

The bodies of both bees and wasps may be very hairy or with only a few hairs. The body hairs of bees are microscopically branched, but wasp hairs are simple. You will not be able to see this difference without a good microscope.

Bees always have wings, but wasps may be winged or wingless.

The drawings have numbered body parts. Similar parts have the same number. Use the boldfaced words to identify those body parts (words are included in the drawings).

hind wings front wings
mandibles proboscis
compound eyes antennae
nodes coxa
trochanter femur
tibia tarsus
metatarsus


Diptera

The order Diptera contains the true flies. You may be familiar with some of the common kinds such as the house fly, horse fly, greenbottle fly and mosquito. Notice that in spelling the common names of true flies, "fly" is a separate word. In the names of insects that are not true flies, such as dragonfly, butterfly, dobsonfly and so on, "fly" is not a separate word. There are many kinds of true flies. Some resemble bees or wasps in shape, coloration or hairiness. In this study you will look at characteristics that separate flies from other insect orders.

The outstanding characteristic of true flies is that they usually have only one pair of developed wings. The second pair of wings are reduced in size to small structures called halteres. The halteres may look like a tiny golf tee projecting from the hind part of the thorax. You may need a hand lens to see it. The halteres on house flies and their near relatives may be hidden by whitish flaps called calypters. Calypters are extensions of the developed wings.

The mouthparts of flies are usually formed into a proboscis for feeding on liquids. The house fly vomits on solid food to dissolve it and then it sucks up the liquid food. Mosquitoes, stable flies and others have a stiff proboscis for puncturing the skin and sucking blood. Some flies do not feed as adults and their mouthparts are undeveloped. No flies have chewing mouthparts.

Most flies have short antennae with few segments, but mosquitoes, midges and crane flies have long antennae composed of many segments. The compound eyes of flies are large and often occupy most of the head area.

The drawings have numbered body parts. Similar parts have the same number. Use the boldfaced words to identify those body parts (words are included in the drawings).

wings halteres calypters
proboscis antennae eyes