Category: insects (Page 35 of 89)

Bug of the Week: Tiny Parasitic Wasp

Our discovery this week is due to some photogenic wild sunflowers.

sunflower-1I was taking a few photographs, when…

sunflower-flying-wasp-18what is that tiny insect flying by?

sunflower-wasp-flying-0006There it is again. Can you spot it?

little-wasp-on-sunflower-13To give you scale, this is what it looks like on a sunflower petal (actually ray flower).

wasp-on-sunflower-petal-40Talk about tiny! It is a parasitic wasp (Pteromalidae).

Why are tiny wasps hovering around a sunflower? It is possible that they are parasites of insects that visit sunflowers. Many species are parasites of insect eggs. It is also possible the wasps are feeding on nectar, although I saw no evidence of feeding. They also could be males waiting for females to visit.

What do you think these tiny wasps are doing?

Bug of the Week: Cicada Season

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

cicada-side-good

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.

cicada-back-19

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?

cottonwood-petiole-gall-122

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

cottonwood-petiole-gall-055

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.

inside-cottowood-petiole-gall-060

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?

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