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Week before last we must have had a spike in humidity levels because all the Texas sage bushes in the neighborhood started flowering. They were so pretty, I thought I'd add a plant of the week this week.

texas sage

Also called purple sage, or Texas silverleaf, the scientific name of this Texas native plant is Leucophyllum frutescens.  They appear gray because their leaves are densely covered with silvery hairs. The flowers may be white, pink, lavender, purple, or blue, depending on the variety. Texas sages characteristically bloom after a rain, or at least a local rise in humidity levels. This interesting trait gives them the common name of “Texas barometer bush.”

texas sage

Check out the white and contrasting spots in the throat of the flower.

Texas sage and other related species are widely planted as water-conserving ornamentals in the southwestern United States. They can get quite big if watered occasionally and allowed to spread to their natural form.

texas sage

It isn’t uncommon to see them pruned as well. Pruning does cut down on the number of flowers, which are at the stem tips.

texas sage

If you are interested in butterfly gardening, you might want to consider planting some of these shrubs. It turns out that they are also hosts for caterpillars, (although I’ve never seen any on ours.) Further south in Arizona there have been reports of caterpillars of the Theona Checkerspot (Chlosyne theona) using the sage as a food plant.

Caterpillars of an attention-grabbing moth called the Calleta silkmoth (Eupackardia calleta) also feed on Texas sage.  If you live in an area where they are found, you should look for them. Check the map at the Butterflies and Moths of North America website linked to the name of the moth.

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It’s cabbage looper season here again. In some places cabbage loopers might be considered to be pests, but in our yard they are considered to be pets. They are hardy, will eat a wide range of foods, and they show up every year.

cabbage looper

The looper gets its name from the fact it “loops up” in the middle while walking. The caterpillar has two sets of appendages. Its six true legs are right behind the head. Towards the rear is another set of fleshy, wider appendages called “prolegs.” Scientists don't count the prolegs, so the caterpillar still has the six legs characteristic of insects.

cabbage looper

The caterpillar holds on with the true legs and brings its back end forward. The prolegs meet the true legs, and the back forms a loop. Then it releases the true legs. The head and front spring forward. The looper holds on with its true legs and the process repeats.

This one was nibbling my mint, but I'm not too concerned. The mint is prolific and the caterpillar has a lot of enemies. It is eaten by birds, wasps and parasitic flies. So, loop on little buddy.

Edit: The cabbage looper moth is featured in a later post.

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A question came in this week that was out of the ordinary and I thought I’d share it here.

Question:  “I have a crazy question and figured that you are the best person to answer it.  On Wednesday, I am leading a class about the skeletal system, and I am anticipating a question from one of the younger kids.  I don’t know how to answer it.  How do insects make their blood?  In humans, blood is manufactured in the bone marrow.  Is the exoskeleton of an insect also responsible for blood production?”

Answer:  An insect's blood is called hemolymph (or sometimes haemolymph), and it circulates around the interior body cavity, between the exoskeleton and the inner organs. It is a yellow, greenish or pale-colored fluid. The hemolymph is moved about by the insect’s hearts and by the movement of muscles, but the whole system is much more open than that of vertebrates. The hemolymph is not carried in closed channels like the arteries and veins of humans; it flows freely.

The liquid part of the hemolymph, or plasma, is about 90% water. The water comes from the insect’s food and what it drinks. The water enters the body cavity through the cells of the digestive tract. Right before an insect sheds its exoskeleton or molts, it increases the volume of liquid inside its body, and thus pressure inside. The insect does this both by excreting less (its "kidneys" are called malphigian tubules) and also by drinking more. The increased pressure is used to expand the new, soft exoskeleton while the insect is molting. After the insect has finished molting and its exoskeleton has hardened, it excretes the excess water to reduce the pressure to normal again.

Within the plasma are cells called hemocytes, which carry out some of the same functions as our white blood cells, such as capturing foreign particles (phagocytosis) and wound healing. The hemocytes are derived from the mesoderm in the embryo (which one of the embryonic tissues). It is thought that the hemocytes formed in the embryo give rise to all the new hemocytes through cellular divisions. Insects don't have anything analogous to human bone marrow.

For the most part, the hemolymph does not carry oxygen, which is one of the important functions of our blood. Instead tiny tubes called trachea carry oxygen in insects. (You can see the outside openings of the trachea on the sides the green June beetle larva in the previous post.) The trachea reach all the way down to the cellular level. Thus, the hemolymph system in insects is more similar to our lymphatic system.

And, there’s no such thing as a crazy question! ☺