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Insects are not always easy to identify.

Take this cute little guy. Is it a beetle or is it a bug?

Because it has a shield shape in the middle of the back and a beak (the mouthparts you see tucked under the head), it's a shield bug (also called stink bug).

Now comes the hard part. Some shield bugs, like harlequin bugs for example, feed on plants. Some are predatory and feed on soft-bodied insects like caterpillars. How do you tell which is which? A rough rule of thumb is if the beak is thicker than the bug's antennae, then it is a predator. If the beak is about the same thickness as the antennae, then it is a plant feeder.

This little guy is a predatory kind in the genus Perillus. Best to let it go about its business.

After so many years of taking photographs of insects in the immediate area, it is still possible to find something new. Take for example this brown bug I found on the petals of a Mexican hat flower.

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It turned out to be a shield-backed bug, family Scutelleridae.

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Shield-backed bugs are relatives of stink bugs, and in fact they used to be in the same family. However, the scutellum (a part of the thorax) is much larger and covers the entire abdomen, including the wings. This structure resembles the hardened elytra of beetles and at first glance shield-backed bugs do look like beetles.

Like some of the more familiar stink bugs, shield-backed bugs feed on plants, particularly members of the family Asteraceae, to which Mexican hat plants belong. They have sucking mouthparts that they use to suck plant juices.

Also like stink bugs, shield-backed bugs have defensive glands that release a pungent scent if the insect is threatened or disturbed.

Discovering a whole new (to me) family of insects this week is quite exciting.

Have you seen any interesting insects this week?

Have you ever seen a shield-backed bug before?

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Spring is about to burst forth here and more insects are starting to appear again.

Take this stink bug, for example. It wandered up out of the foliage while I was watering.

How do I know it is a stink bug, family Pentatomidae? First of all, it has a wide, flat back that is shaped like an old-fashioned shield. That is why another common name for this group is "shield bug." I know it is a bug because of the triangular-shaped piece in the middle of its back, called a scutellum.

Why are they called stink bugs? Many members of the Order Hemiptera release a distinctive odors from special glands whenever they are disturbed. Some of the odors, but not all, are unpleasant. This one never produced an odor while I was watching it.

As a group, stink bugs are unusual because some are plant feeders and others are predators of insects. How do you tell which one you have? If you are an experienced entomologist you will check the proboscis, or straw-like mouthparts. The plant feeding types have a thinner, more flexible proboscis.

The fact it is feeding on the lettuce I offered it is another big clue. 🙂

Check out the cool illustration of stink bug anatomy I found:


(It is by Giancarlodessi at Wikimedia)

A: head; B: thorax; C: abdomen.
1: claws; 2: tarsus; 3: tibia; 4: femur; 8: compound eye; 9: antenna; 10: clypeus; 23: laterotergites; 25: pronotum; 26: scutellum; 27: clavus; 28: corium; 29: embolium; 30: membrane.

(27-30 represent parts of the wing)

Stink bugs aren't the prettiest insects in the world, but don't you think they are more interesting once you get to know them?