Year: 2013 (Page 17 of 59)

Seed of the Week: Ruellia

September 24, 2013 / Roberta / 1 Comment

Our mystery seeds from last week came from a plant with bright purple flowers, the common ruellia, Ruellia tweediana (previously R. brittoniana).

Ruellias are also called desert or wild petunias because their flowers resemble petunias, although the plants are not closely related.Â Usually the flowers are purple, but some varieties are pink or white. There is also a dwarf form.

Common ruellias can be quite aggressive unless constrained. The plants can spread vegetativelyÂ underground or by seeds and they are considered an invasive weed in many places.

In fact, one kid-friendly aspect of some ruellias is that the pods shoot open to release their seeds explosively, as shown in this video:

Here in Arizona we have a native ruellia called wild violet petunia (Ruellia nudiflora) that would make a great substitute for the invasive kind.

Does ruellia grow where you live?

Bug of the Week: Dragonfly Nymph

September 18, 2013 / Roberta / 2 Comments

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

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.