Male Monarch

Here's a good picture that makes it easy to determine the sex of your Monarch butterfly. You can see what looks a little like a pair of dots superimposed on the veins on the back wings. These usually stand out pretty prominently when you're looking at the top of the wings; they're harder to see when the wings are up and you're seeing the underside of the wings.

These spots are scales that, in other butterflies, release pheromones that help females find males. (Apparently we're not sure that they're doing this for Monarchs.)

A more subjective way of telling the difference between males and females is to look at the thickness of the veins. The veins on the males are usually noticeably thinner than you'd see on females. You could also argue that the thinner veins of the males make their pheromone dots stand out more than they would if they existed on the thicker female veins.

July 28, 2021 at Sourland Mountain Preserve
Photo 148655927, (c) jpviolette, some rights reserved (CC BY-NC)


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