Month: September 2013 (Page 2 of 5)

Bug of the Week: Dragonfly Nymph

Yes, our mystery insect last week was actually the exoskeleton or the shed “skin” of a dragonfly nymph.

dragonfly-nymph-exoskeleton

Dragonfly nymphs usually live under water, but they crawl onto land before emerging as adults. Exposure to the air and sun has darkened this exoskeleton and made it look, well, crispy.

You can tell the adult dragonfly has emerged because of the opening in the back of the thorax. Those white lines are the remnants or linings of the breathing tubes (tracheae) that pull out as the adult dragonfly emerges. The adult will produce new tracheae.

The one feature that really tells that this is a dragonfly nymph is the head, particularly the “mask” at the bottom of the face. Dragonfly nymphs have a special lower lip or labium that they use as an “insect net.” It not only shoots out to capture or scoop up prey, but also holds food while they eat, sort of like a horse’s feed bag.

In this video of a live dragonfly nymph feeding, look for both uses of the labium.

Isn’t that cool?

I loved reading all the imaginative ideas about what the insect might be. Would you be interested in future mystery insects?

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If you would like more dragonfly science, try this previous post with activity ideas.

Seed of the Week: Honey Mesquite

Our mystery seeds from last week were indeed from a mesquite tree, in particular the Texas honey mesquite, Prosopis glandulosa.

honey-mesquite-2

Honey mesquites are popular landscape trees in the Southwest. They are known to produce a low, very wide canopy.

honey-mesquite-leaves

The compound leaves form a drooping, upside-down Y-shape. Can you see the Y?

Some of the mesquites can be hard to tell apart. For example, the screwbean mesquite also has Y-shaped leaves, but they tend to be shorter and more compact. The screwbean mesquite seed pods are also distinctly different from those of the honey mesquite.

honey-mesquite-branches

The honey mesquite has drooping leaves and branches that give a delicate appearance, almost like a weeping willow.

honey-mesquite-flower

The flowers are long and pale yellow. Honey bees often collect nectar from these flowers.

honey-mesquite-tree

Overall, the honey mesquite is a “sweet” tree if you live in the Southwest.

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