When we think of animals and ecosystems, we often think of vast savannas, rushing rivers or lush jungles. For many people, the ecosystem is a giant place where multitudes of plants, animals and other organisms live. But sometimes, an ecosystem can be very small, with much of the action taking place on just a few square inches.
Here at GROW, we’re fortunate to have a sophisticated Leica brand microscope, one that allows us to connect a mobile device or computer screen to an on-board camera to capture images of whatever we’re examining that day. We often pluck milkweed leaves from our outdoor space to view with our guests. Over the summer, we’ve snapped photos of a surprisingly diverse spread of insects that call the tiny space of a leaf their home. Enjoy a collection of some of the best photos we’ve taken to truly capture what life is like on a milkweed leaf.
If you pull a leaf at random from one of the milkweed plants, chances are you’re going to see at least a few bright yellow specks dotting its surface. Those specks are the brightly colored milkweed aphid. Aphids are infamous among gardeners as a near-universal pest. They use a long proboscis (similar to a butterfly’s) to suck plant sap from the leaf, which can turn it brown and cause it to wither. While there are hundreds of species of aphids, most are monophagous, meaning they only will eat from one specific type of plant.
A unique attribute of aphids is that unlike a lot of other insects, aphids give live birth rather than laying eggs. As a result, aphid populations can quickly expand and take over entire plants. During the winter months, aphids will lay eggs to hibernate and survive the cold weather before going back to live birth in the spring and summer months.
When a leaf becomes too crowded to support more aphids, some females will molt their outer skin to develop wings. The wings allow fertile females to fly to other plants to continue to spread the aphid population.
Adding to the aphid’s arsenal of survival are two black tails called cornicles. These cornicles are tubes that can release a quick-hardening liquid called cornicle wax that is used as a defensive measure against aphid predators.
But wait… why is that aphid brown and dried up?
Aphids have a lot of predators in this tiny world, and many opt for a parasitic mode of attack. The aphid wasp is a parasitic insect that will lay eggs inside of an aphid, where the wasp grub eats the aphid from the inside out. After emerging, the shell of the aphid dries up and becomes an “aphid mummy.”
(Disclaimer: the grub pictured above is not an aphid wasp, as they only emerge when they are adult wasps. We have yet to get a positive identification on what that grub is.)
Other aphid-eating insects take the vampiric route: biting an aphid and sucking out its bodily fluids until the predator is nourished. This ladybug larva is tiny and at most only a day old, but it’s already a hungry predator.
This ladybug larvae will grow up to be a hyperaspis ladybug, a species with a black shell and orange spots. Hyperaspis larvae produce a waxy, stringy coating as they grow up, a coating which protects them from would-be predators. Eventually, the larvae will curl up and form a cocoon before undergoing metamorphosis and becoming an adult ladybug.
It’s not a caterpillar you see before you, it’s another baby bug with a vicious appetite for aphids. Unlike the jaw-like mandibles of a ladybug larvae, this hoverfly larvae is equipped with a piercing proboscis to dine on aphids. While it may seem gruesome, it’s the most efficient way to get meals as a tiny insect. It’s hard to break apart the hard exoskeleton of insects like aphids, so methods that attack the soft interiors of insects are the easiest way to deliver nutrients to a predator.