Spotted lanternfly (SLF) egg masses are laid in the late summer and into the early winter, with the majority of egg mass deposition occurring in October. These egg masses survive winter and hatch into SLF nymphs in the spring. Each egg mass contains an average of 30-50 eggs, and an individual female can lay at least 2 egg masses. These egg masses are the only stationary stage of the SLF, making them an easy target for removal. However, there are a few things you should know before you proceed to squash and scrape!

Identifying Egg Masses

SLF egg masses are usually about 1.5 inches long and colored brown/grey; however there can be a lot of variation among them! All egg masses contain rows of small eggs, roughly the size of a sharpened pencil point. Rows can vary in length, with some being longer than others in the same egg mass. Eggs within the egg mass can vary in color from a yellow to brown. After the female lays the eggs, she covers them with a substance believed to help them survive winter conditions and protect them from predation. When this substance is first deposited, it is white and glossy. After a few hours, the substance becomes duller and dries to a darker grey/brown color. Some egg masses do not get covered, often because the female SLF was disturbed by outside factors such as humans, other SLF, or potential predators. We have found that egg masses without a covering have a 10% lower hatch rate on average, though they can still hatch. Egg masses that have not been laid by the female will not hatch – if you kill an adult female SLF that is full of eggs, you need not do more!

Egg mass cases that were laid up to 2 years ago can still be found on trees and other structures – the easiest way to distinguish a fresh egg mass from an old one is to (1) check for the presence of the covering on the top of the egg mass and (2) check for the presence of emergence holes. The covering fades with time and while it is often still present in the spring, it may look dry and cracked. After the eggs hatch in the spring, the remnants of the egg mass weather even more, making the covering often disappear altogether. Additionally, each egg mass is equipped with a top "hatch door" that nymphs use to escape out of in the spring. These emergence holes are a perfect oval at the top of each egg. If these are present, the egg mass is old and nymphs have already hatched from it.

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