It must have rained last night. We awoke this morning to cooler water.
This is a very exciting day for us! Gyro reports that we are on schedule to arrive home at Duckweed Base before noon. All aboard are excited with the prospect of several days of rest and relaxation before continuing on with our biological survey mission. The crew has performed splendidly on this first voyage. My report to the Micro Exploration Institute will praise these courageous explorers. I will be recommending promotions for everyone!
10:15 hours… Gyro reports a concern. He is feeling a bit of a cross current against the wheel. To my distress the current increases with each passing minute. I can only guess that the rain in the night has flooded the pond, and that we have encountered an uncharted outflow current. Barron reports from the engine room that we don’t have enough power to escape the current.
A moment later my fears are confirmed. We are being swept out of the pond, powerless and out of control!
10:20 hours…
We are caught in the rapids!
Enormous stream rocks streak past the windows as the current whisks the Cyclops downstream. Our friends at Duckweed Base will worry when we are overdue. I am hoping that they send out a scout to find us. In the hopes that they do, I order the crew to shoot a signal flare. Maybe somebody will see it!
When we gain control of the ship again we are stunned by the presence of many animals crawling around the stream rocks. They all have hard shell-like coverings, bodies in three sections, and six legs – they are insects! Because they are living in water, we must be seeing the larval stage of an adult insect that normally lives above water, in the air, or on the land.
One type of insect, mayfly larvae, have flattened bodies for living on the rocks without being whisked downstream by the powerful current. Their streamlined bodies and hooked feet allow mayflies to crawl over stream-swept rocks, scouring the surfaces for food. But what are they eating? A close look at the surface of a sunlit rock reveals the answer. Diatoms – just like the ones we found living in the pond! These photosynthetic algae cells cover the rocks, and provide food for the mayflies.
12:35 hours… further downstream we see a jumble of sand grains moving about! A closer peek shows that this pile of sand grains is a house for another stream insect– a caddisfly larva. Some caddisflies build houses from sand grains, others from small sticks. The insect’s head and legs emerge from a tube-like house that protects it from stream predators such as fish and other insects.
13:20 hours…
Swept into a slow moving pool, we see a savage monster of the stream insect world.
This very large insect larva goes by the well-earned name of water tiger! It is a fierce predator, as we soon observe.
The water tiger attacks a tadpole. Its long, needle-sharp fangs pierce the poor pollywog, which quickly becomes still.
We believe that the water tiger injects some kind of toxin into the tadpole, paralyzing it, and turning the internal organs into soup.
After a minute a ghastly feast begins. Through its fangs the water tiger begins sucking in the tadpole’s liquified insides.
What a surprise, to find an insect that preys upon more complex animals. Tadpoles and small fish are no match for the fearsome water tiger!
Although most likely too small to grab its attention, we steer clear of the feasting water tiger and continue our white water journey down the stream.
The Insect Body Plan
All insects have bodies in three sections: head, thorax, and abdomen. The head contains eyes, brain, mouth, and antennae. The thorax is where legs and wings attach. The abdomen has reproductive organs and the intestine. Insect larvae and the adults they become have the same body plan. Wings do not fully develop until the insect emerges from a pupa and begins life above the water.
