This reader found “small white/yellowish larvae floating on silk threads in Northern Michigan” and states that they were “coming out of oak trees”. Besides the photo attached below, this is all the context provided, but we will do our best to provide information on these larvae.
Although no questions were attached to our reader’s query, we assume he wishes to know what these are. Now, the photograph is quite blurry, and we cannot really make out the organisms (unless the glowing, white object seemingly floating near the bottom of the photo is one of the larvae hanging on a thread). Despite this, we can still make an educated guess about the identity of these larvae based on the context our reader provided. It is our opinion that these may be oak leaf rollers.
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Oaf leaf rollers are the caterpillars of the oak leaf roller moth (Tortrix viridana). These caterpillars are actually green in color, but can appear to be a pale yellow or white in bright lighting. These caterpillars are oak defoliators, meaning that they feed on the leaves of oak trees, which they do at quite an early stage in their maturation. If numbers of oak leafrollers are particularly high one season, then these caterpillars can actually completely defoliate an oak tree. That said, this is not necessarily harmful to the tree, as it will regrow its leaves.
As our reader alluded to, oak leaf rollers can indeed produce silk threads which they hang from. This is the same silk they later use to construct their cocoons, in which they metamorphose into a moth.
Oak leaf rollers are completely harmless. The biggest threat they pose is as a nuisance. The wind will often blow them off the treas and onto (or into) people’s cars and clothes, to which they cling for dear life. They have also been known to invade homes, though this is also accidental and can be blamed on the wind. So, if our reader were to find any of these in his home, he should just move the caterpillars back outside, preferably near an oak tree.
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In conclusion, we think that the larvae our reader found “coming out of the oak trees” are oak leaf roller caterpillars. They are nothing to be feared, so our reader need not worry for his health and safety. We hope this article helps, and we wish him the very best.