If your kids had fun with the “Putting the Leaves on the Trees” activity last week, check this post from the Urban Science Adventures website, called Urban Wildlife Watch: Ash Trees.
Category: Find Out More (Page 13 of 20)
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?â€
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! ☺
Several weeks ago I wrote a post about a mystery in our back yard. You may recall that bits of glass were appearing on our patio and in our yard, particularly near where we had water available. I wasn’t sure how the pieces were getting there.
After reading my post, my son “confessed†he was the source of the glass chip. It was from a broken bottle. He also pointed out, however, that he had found bits of glass mosaic near another part of our lawn where water collects periodically.
As you may have figured out from the title of the post and the feather clue, I think the culprit is a bird. We have many birds that regularly visit our yard, including house finches and a variety of doves. But the evidence points to other regular visitors:Â the great-tailed grackles, Quiscalus mexicanus.
The great-tailed grackles look like regular grackles, except the males have a much longer tail. The female great-tailed grackles are brown, whereas female regular grackles are black. The males have iridescent colors on their necks and backs, similar to pigeons. Here is a female:
One of the most striking aspects of great-tailed grackles is the male’s display to females. The male raises his beak to the sky, straight up. A bunch of males often perform this behavior together.
Why do I think the grackles may be involved in the glass mystery?
Clue Number 1:
Many people have reported that crows and magpies are attracted to shiny objects, and often “steal†things away to their nests.
In fact, one of their relatives, the starling, has been caught in the act stealing money from a car wash.
We do get an occasional starling, but the grackles are in the yard for long periods every day.
Clue Number 2:
Grackles are known to dunk hard pieces of food in water to soften them. For evidence, see this video. The video is rather long, but the section that shows the dunking behavior by the birds starts right after the written commentary.
Clue 3. Great-tailed grackles have been reported to drop chicken bones from trash into people’s back yards.
Clue 4. Grackles have been reported to toss berries or small stones to one another.
Although the evidence implicates the grackles, I have yet to catch them in the act. They are obviously smart and playful birds and it may be hard to find out for sure what they are up to. If I do, I will let you know.
If you are interested in bird behavior, check these books for more information.
The Sibley Guide to Bird Life & Behavior by David Allen Sibley
The Life of Birds DVD by David Attenborough
If you are interested in birds and/or flight, this is a stunning movie.
Winged Migration (2001) Starring: Philippe Labro, Jacques Perrin Director: Jacques Perrin, Jacques Cluzaud Rating: G Format: DVD
For more information, see Roberta Gibson Writes.