The dusky birch sawfly has an interesting lifecycle
This tiny green caterpillar looking creature is called a dusky birch sawfly. As the name suggests, the host plant this species prefers is the birch tree. It can be found throughout the United States, but is typically seen in the eastern United States. I took this photo in Northwestern Massachusetts in the month of September.
The dusky birch sawfly has an interesting lifecycle. Females will lay eggs on the underside of birch tree leaves. When the eggs hatch, larvae will immediately start consuming the birch tree leaves. During this time, the other sawfly larvae stick together so you often see multiple individuals at once. The larvae will molt several times as they grow. Eventually, they will drop from the tree to the soil to pupate. The larvae create a cocoon-like cell to transform in. When the environmental conditions are right, the adult sawfly will emerge.
Dusky birch sawflies tend to only live long enough to reproduce. Their common name is derived from the saw-like construction of their ovipositor. What is an ovipositor? An ovipositor is an organ used by some insects to lay their eggs. The sawfly will use the serrated edge of their ovipositor to cut into leaves and stems. Then the female sawfly will deposit her eggs, continuing the cycle of life.
Interestingly, I observed and later read that these sawfly larvae make the shape of an “S” when you get close to them (as this photo also indicates).
An ovipositor is an organ used by some insects to lay their eggs
Did you know?
- There are more than 8,000 species of sawfly!
- Sawflies can be found across the world, including every continent except Antarctica.
- It generally takes 2-8 weeks for sawfly eggs to hatch. This time will vary based on the species of sawfly and the temperature of the environment.
- Dusky birch sawflies, despite looking like a wasp, cannot sting.
- Although these creatures are notorious for defoliating trees, they generally do not affect the plant’s health.
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