How Big Do Monarchs Get
The size of monarchs varies, like all other living things, from their beginning stages of life through full adulthood. The size of the monarch egg is between .9 millimeters and 1.2 millimeters. Once the egg hatches into a larva, it will then begin as a small, worm-looking creature from as little as 2 millimeters to 6 millimeters.
Over the course of about two weeks, the larva will begin to grow and change colors, into a full-sized caterpillar, which can range from 25 millimeters to as big as 45 millimeters, before it finally makes its way to a sturdy leaf, where it will build its chrysalis.
The size of the chrysalis directly correlates to the size of the caterpillar. The bigger the caterpillar grew before going into its pupa stage, the bigger the pupa will be. The size varies based on a few factors, such as genetics and whether or not the caterpillar was able to eat enough food before going into metamorphosis mode.
Once in their butterfly stage, male monarchs are bigger in size compared to their female counterparts. Monarchs in general can range from 89 to 105 millimeters, determined by their wingspan, which is about 3.5 to 4 inches in length. You can tell the difference between a male and female monarch by looking for black dots on the veins of their wings. If there are black dots present, known as the odor glands, then the monarch is a male. These are the glands that produce the scent to attract a female monarch. If there are no black dots, then the monarch is a female.