The fall webworm moth can now be found in many parts of the world
I saw this brightly colored caterpillar while I was hiking at Eagle Creek Park in Indianapolis. This fuzzy fellow will grow up to be a white moth known as a fall webworm. It is primarily known for the webbed nests that the caterpillar’s make at the end of the larval stage. These cover tree limbs of hardwood trees in late summer and fall. It’s seen as a pest, but the nests don’t harm healthy trees.
Native to North America, the fall webworm moth can now be found in many parts of the world. This moth was introduced in the 1940s in Europe, and it has spread its range to cover the entirety of the continent. They are seen as an invasive species in East Asia. They are seen in Turkmenistan, Uzbekistan, Kyrgyzstan, and Kazakhstan. In 1945 it was introduced to Japan. If you’re visiting China, Mongolia, Korea, or Russia, you may find this global moth.
Each year, one generation of this moth appears in North America. The larvae appear in late summer through early fall. The 40° north latitude demarks how many generations will appear. South of this line two or more generations can appear in a year. The adults will lay eggs on the underside of leaves in hair covered clusters of a few hundred eggs. It takes about a week for the eggs to hatch. The larval stage involves brightly and variably colored caterpillars. They range from pale yellow to dark gray. The fall webworm moth will have yellow spots, and both long and short bristles, giving them a fuzzy appearance. They also have two cream stripes along the side. The caterpillars grow to a length of 35 mm.
As mentioned previously, this math will create webs on the end of tree branches. Inside of these webs and they will consume the leaves of the tree. The stage less for about six weeks. The final stage before they emerge as adults is the pupa stage. They overwinter in the bark and leaf litter at the base of trees. The paper is only 10 mm long and is dark brown. The cocoon is made of silk and detritus. When the Delta merges, it is known to be quite hairy and is white in color. The males have black or brown spots on the fore wings. The females are almost entirely white with a sprinkling of brown on the abdomen.
The larval stage involves brightly and variably colored caterpillars
Did you know?
- The fall webworm moth is known to be among the most polyphagous of insects, meaning that it will eat many different species of trees. It has been known to eat from over 630 different species.
- As larvae, they will defend themselves by shaking and jerking together and producing a repellent scent
- Fall webworm moths calm down to experience behavioral thermal regulation. They maintain a temperature of around 40 to 50°C within their web.
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