Year: 2013 (Page 29 of 59)

Bug of the Week: Thistle Tortoise Beetle

Our featured insect can be quite difficult to spot on a plant.

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Do you see the insect? I’ll give you a hint: The head is covered.

You can see why it is called a tortoise beetle. In fact, it is the thistle tortoise beetle, Cassida rubiginosa.

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The thistle tortoise beetle has an interesting history. It was introduced into North America because it feeds on a weed that was accidentally introduced earlier, the “Canada” thistle. By the way, the “Canada” thistle is actually from Europe, where it is called the creeping thistle. Shows you how misleading common names can be! In any case, the thistle tortoise beetle is an insect that was purposely brought in for weed control.

The larvae of this species (see BugGuide) carry debris and feces on their backs to discourage predators. Wish I had found one of those.

These photographs were taken in western New York.

Have you ever seen a tortoise beetle? Was it green like this one?

 

Seed of the Week: Daffodil

The mystery seeds from last week were from a daffodil, Narcissus sp.

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Gardeners usually plant daffodils as bulbs, but the plants also make seeds.

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The seeds form in capsules.

Why don’t we plant more daffodils from seeds? It turns out that germinating daffodil seeds can be a bit tricky. The seeds often have special structures called “elaiosomes” that attract ants. The ants carry the seeds to their nest, where they eat the elaiosomes and toss out the seeds into their trash heap, which is usually a chamber in the soil. The conditions in an ant mound are often ideal for seed germination and the seeds eventually grow.

The relationship between the ants and the plants is quite specialized. The presence of the elaiosomes may even inhibit germination in some species, so the seeds won’t germinate until the elaiosome has been removed (by an ant). Cool!

It turns out that many plants, especially our spring wildflowers like Trillium and Viola, are planted by ants.

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It’s amazing what you can learn by being on the look out for seeds.

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