February 26, 2021

Yes, you read that right. We’re announcing the hatching of a [checks notes]…Malaysian Giant Leaf Insect?

If you’ve been to the Insectarium, chances are you’ve already been captivated by the Malaysian Giant Leaf Insect’s whimsically convincing camouflage: they look like leaves, down to the leaf veins and browning edges.

So convincing is their deception that sometimes they even fool each other. In an act of “accidental cannibalism,” Giant Leaf Insects, which eat — you guessed it — leaves, think that they’re chomping into a leaf when they’re taking a bite out of their sister.

The key word here is sister. Males of this species are so rare; they are almost non-existent. In over a decade of keeping colonies at the Museum, thousands of their eggs have hatched. Of those, only two have been males (this special guy being the second).

We think of science as long-established knowledge, but the first Malaysian Giant Leaf Insect (hereafter referred to as Phyllium giganteum) wasn’t discovered and described until 1984. There was no evidence of any males of the species at all until 1994. Just about every single individual Phyllium giganteum are females, and those living in colonies, like the one in the Insectarium, are each others’ sisters, daughters, and mothers.

There may be a question forming in your mind since it’s not the sort of thing we often talk about in polite company. But how does…? What about…? Don’t they…?

Let’s amend the birds and the bees story a little. There are rare cases in nature of parthenogenesis, a type of asexual reproduction where a female can lay an unfertilized egg that still produces offspring. Some snails, lizards, insects, birds, sharks, and snakes show this reproductive behavior.

We don’t know how or why asexual reproduction occurs in such different types of animals. Some scientists believe it is an evolutionary “last resort.” If a female has no other choice because there are so few males around, then she can reproduce asexually.

But back to our Giant Leaf Insects, this doesn’t seem to be the “last resort” with them. It seems to be the primary way that they reproduce. Females produce generation after generation of unfertilized yet viable eggs. These eggs hatch into yet more females that are nearly genetically identical to their mothers.

So, if successive generations are basically clones of the previous generations, how did we get a male?

While we’re asking how this is possible, we might also ask with this type of reproductive strategy, what does it mean to be male or female?

Phyllium giganteum don’t have Y chromosomes. Their number of X chromosomes determines their genetic sex: females have two, while males have one. That single X male sex chromosome may result from a simple mutation in the egg.

But we don’t know how many X chromosomes our male has. Some Phyllium giganteum exhibit male traits but still have two X chromosomes. Others still may have a different number of chromosomes in different cells.

We still have much to learn. Our categories are imperfect for describing the boggling variation of life that we simply don’t understand very well.

This unlikely little brother is more evidence that science isn’t done yet. This improbable male reminds us that we don’t have all the answers. We might not even know the right questions yet.

About the authors

Peregrine Bratschi is the Associate Program Manager for the Lab at the Museum and facilitates in-person programming and the virtual Lab@Home series.

Max Cawley is Program Manager for Public Engagement with Science at the Museum, where he manages projects at the intersection of research, policy, and the public.