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Exploring Dragonfly Larvae under the Microscope

Dragonflies have always been fun to watch and catch but have you seen one when it was still a little larva? More than that, have you ever looked at a dragonfly larva under the microscope? This is an interesting science microscope activity that teachers can suggest to their students.

Observing dragonflies can be done even at its very first stages of growth. Children can observe dragonfly larva with their microscope for kids. These larva are not very hard to find and you can often see them clinging onto some water weed. If you observe the larva using the most basic simple microscope, which is really just a magnifying lens, you will see that they have appendages that are like arms and with teeth-like spines that grab its prey.

The students can obtain the larva and put it on a watch glass. Drop one percent of chloretone, a weak local anaesthetic, to sedate the little creature. Under an educational microscope, we will first try to find out its breathing process. Focus the low power stereo microscope on the lower part of the insect where the rectum is located. This is where the tracheal gills are located. These tracheal gills are branching air-tubes of insects that is equivalent to an animal’s lungs. At each side of an insect’s body, there are openings called spiracles that receive the air. The air is then scattered throughout the body by the trachea.

The dragonfly’s larva has tracheal branches that are bathed by water. The rectum sucks this water and derives the oxygen from it. The oxygen then passes through the ramifying trachea which distributes the air throughout the insect’s body.

Another interesting aspect for the student to observe under the microscope from a dragonfly larva is its circulatory system. A larva’s heart consists of a series of chambers with a valvular opening called ostium. The ostium allows the blood inside the chambers and is allowed to flow forward and be released to another end.

Under the scientific microscope, the heart can be seen located under the skin at the posterior end of the abdomen. At the front portion of the heart, you will see a slender tube that is the aorta. The aorta will be seen passing through the thorax and into the head where it divides under the brain into two branches. This is where the blood leaves the aorta and then spreads out throughout the body.

The circulation of the blood can also be easily observed in the science classroom by the student using a stereoscopic binocular microscope. If you look closely you will see that the blood currents bathe all the tissues as it passes along the muscle spaces, trachea and nerves. Under a low power stereoscope, you can also see the course of the blood currents. In the antennae and legs, you can see that outgoing and ingoing blood streams.

Teachers can also let their students trace the blood currents as it enters the heart ostium and flows inside the heart chambers and eventually is pumped out of the aorta. The heart rate can also tell the activity of the insect. It is said that a faster pulsation of the heart means a more active larva.

When selecting from microscope lessons for the students to participate in, the high school science teacher may find that looking at dragonfly larvae under the stereoscope is one of the better activities. Both students and teachers will find it fun and enjoyable viewing these small creatures who grow up to be facinating acrobatic fliers.

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