Month: April 2011 (Page 2 of 4)

Bug of the Week: Seed Beetle Life Cycle

Last week we looked at the life cycle of grasshoppers, now we are going to find out more about seed beetles.

We have often seen seed beetles feeding on pollen and nectar from flowers. Where do they come from?

We had picked up some seeds for our regular “seed of the week” feature, and put them in a vial. When the time came to take the photographs, we discovered we had collected more than seeds.

The vial was full of tiny seed beetles (a different species than above).

You can see where the beetles had emerged from the neat round holes in the reddish-brown seeds. What are the light-colored things that look like sesame seeds on the surface?

Those are the eggs of the seed beetles. Because they were trapped in the vial, the adults were laying eggs on the seeds they had emerged from. The eggs will hatch into larvae that will tunnel back into the seeds. After feeding. molting and growing, the larvae will pupate. The pupa then transforms into the adult beetle. The adults cut through to the outside of the seed to continue the cycle.

Can you see the neat round caps the beetle cut from the seed coats on the ground to the left? Those few seeds produced quite a few beetles. Most had two exit holes per seed.

Imagine being small enough to complete your life cycle within a single seed!

Seed of the Week: Scarlet Flax

The mystery seeds from last week were from a beautiful annual flowering plant called commonly called red flax or scarlet flax, Linum grandiflorum.

Originally from North Africa, the scarlet flax is drought tolerant and grows well in Arizona.

As you can see, it produces lovely bright red flowers.

Does scarlet flax grow where you live?

Note:  Mystery seed will be back next week.

Bug of the Week: Grasshoppers and Growth

We found a grasshopper this week.

Not full grown like this one from last summer.

It was a newly-hatched grasshopper, small enough to fit in the center of a desert marigold flower.

How do you tell that this isn’t a really small adult grasshopper?

The young stages of insects with incomplete metamorphosis, like grasshoppers and praying mantids, look like miniature adults without wings. The young are called “nymphs.” They start out small, and grow each time they shed their outer covering, called the exoskeleton.

(Drawing by Snodgrass retrieved from Wikimedia.)

See the long wings that cover the back of the adult stage? Some of the older nymphs have short wing buds where the wings are going to be. The antennae are longer in proportion to the body in adults, as well.

Where do grasshoppers start out their life cycle?

(Drawing by Snodgrass retrieved from Wikimedia)

The adult female grasshopper lays a cluster of eggs in the soil. When the eggs hatch, the tiny nymphs crawl to the surface and begin feeding on plants. Thus, the cycle starts anew.

So, is this brilliant green grasshopper an adult or a nymph?

Edit:  Note this life cycle is a generalized summary of the typical insect. With over 1,000,000 described species of insects, there are of course a number with shortened, reduced or even no wings as adults.

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