Bug of the Week

Do you remember our post about butterfly identification for beginners?

At long last, here are the answers to the identification quiz:

1. What family does this black, white and blue butterfly belong to?

Mystery-butterfly-1-identificationThe sharply contrasting colors and wings that are long than wide let us know that this is a member of the family Heliconiidae. These butterflies are commonly called the heliconians. The butterfly in the photograph is a Sara longwing, Heliconius sara.

2. This brown, orange and white butterfly has one unique characteristic found in no other families. What is it?

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Can you see the very long nose or snout? This butterfly belongs to the family Libytheidae or snout butterflies.

3. What family does this butterfly belong?

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With its white color and somewhat rounded wings, it is a member of the family Pieridae. These butterflies are commonly called whites, sulphurs, and orange-tips.

How did you do? Do you feel more comfortable identifying butterflies now?

Have you ever wondered about the lumpy growths you see on leaves or stems?

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In this case the lumps are galls formed on the petioles of cottonwood leaves. This tree was covered with them.

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A lot of different insects and mites cause the plants to form galls, so I was eager to take an example home and see what was inside.

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Inside the gall I found numerous tiny insects covered with a waxy powder. Looking under a microscope, it became clear these were nymphs of the poplar petiole gall aphid, Pemphigus populitranversus.

The poplar petiole gall aphid (also known as the poplar petiolegall aphid in scientific literature) has a complex life cycle. The aphids overwinter as eggs on cottonwood twigs. When the leaves unfurl in the spring, the aphids hatch and begin to feed on the leaf petiole. The plant responds to the feeding by producing a localized growth, which becomes the gall. The aphid nymphs move within the gall and continue feeding.

When the aphids complete their life cycles, the galls split open and winged adults fly to plants of Brassica spp. There the aphids feed on the plants' roots in the soil. In this stage, they have a second common name, which is "cabbage root aphid." Eventually, at the end of the season, winged forms fly back to cottonwood trees to lay the overwintering eggs.

There are more to aphids than you might think. Many have similar complex life cycles, where they live on annual plant hosts in the summer and fly to woody, perennial hosts in the winter.

Have you ever spotted a gall on a plant? What kind?

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?