Category: insects (Page 35 of 88)

Bug of the Week: Cicada Season

Right in time for Father’s Day, we heard our first cicada singing yesterday.

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It seems like the local Arizona species of cicadas always start singing the third week of June, or around Father’s Day. They are highly predictable.

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Of course our annual cicadas aren’t as wondrous as the red-eyed periodical cicadas.

Snodgrass_Magicicada_septendecim(Public domain illustration by Snodgrass from Wikimedia).

You have probably heard about periodical cicadas. The adults emerge in large groups after long period underground. Some come out every 13 years. Others spend a whopping 17 years underground.

 

Magicicada_septendecim(Public domain photograph of 17-year cicadas from Wikimedia).

How easy is it to predict when a given insect will emerge or arrive in a certain area? The annual emergence or migrations of insects may depend on weather factors, such as temperature, winds, rains, etc. Those in turn change the availability and timing of host plants, which influence insect development. Insect emergence is often unpredictable, although scientists have created complex mathematical models to track certain pest species.

Cicadas, on the other hand, are protected underground. They also feed on fairly stable hosts, namely trees. Perhaps it is a combination of those factors that allow cicadas to be so predictable relative to other insects.

By the way, some broods of the periodical cicada are emerging in 2015, mainly along the Mississippi River basin area. Check Magicicada.org for more details and links to citizen science projects.

Are the cicadas singing where you live? Have you ever seen an emergence of the periodical cicada?

Bug of the Week: Poplar Petiole Gall Aphid

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?

Bug of the Week: Shield-backed Bug

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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