The Aquarium turns to a beneficial native insect to help control a pest in our Mangrove Reef exhibit on Level 1.

When scale insects, a common agricultural and houseplant pest, showed up on some of our mangrove trees in the exhibit across from the Trust Family Foundation Shark and Ray Touch Tank, the primary biologist for the exhibit looked to nature to control the insects.

Scale insects can be found feasting on plants all over the world. They are usually small and hard to spot at only an eighth to a half inch long. When they are at their smallest, newly hatched from their eggs, scale “crawlers” will traverse their host plant and neighboring plants looking for a good place to settle down. This is when their relationship turns parasitic. Once mature, the female scale insects sink their mouthparts into the host plants and drain it of its sugary sap. Many species will lose their legs entirely, and never move again.

hundreds of scale insect crawlers
(Photo: Christina Minniti/New England Aquarium) Hundreds of scale insects crawl on a mangrove tree leaf.

Enter the green lacewing (Chrysoperla rufilabris), a harmless North American insect nicknamed the alligator bug for its pincher mouthparts and voracious appetite for smaller insects.

The green lacewing larvae hunt and eat scale insects by the hundreds. They are generalists and will take out many other common pests, including aphids, mites, thrips, and whitefly. When they metamorphose into flying adults, they will no longer eat other insects, but transform into beneficial pollinators. Here at the Aquarium, we offer them a specialized, sugary feed so they will stick around and make more babies.

Lacewing larva
(Photo: Jack Dynga/USDA) A lacewing larva dines on whitefly nymphs.

Introducing these beneficial insects is part of a larger Integrated Pest Management plan (IPM) for the Mangrove Reef exhibit. When plants are kept outside of their native range, they may no longer be living in optimal conditions (needing more or less humidity, light, or different temperatures). This can have a toll on their immune defenses to stave off pests. Designing an IPM for our exhibits, or your houseplants at home, starts with optimizing these variables, known together as “cultural care.”

Aquarium Biologist Christina Minniti first monitored the lighting, air temperature, and humidity in the exhibit to see if cultural improvements could be made. It’s no surprise that through the winter the humidity levels were low. But even through our muggy New England summers, the building’s air conditioning can zap moisture from the air. Once she was able to confirm good cultural care, including bringing the humidity inside the exhibit closer to the 70% Rh that mangrove trees crave, she could finally introduce the beneficial insects.

uncut strips of lacewing eggs.
(Photo: Christina Minniti/New England Aquarium) These paper strips of eggs will be separated and then hung in the mangrove exhibit.
lacewing larva
(Photo: Christina Minniti/New England Aquarium) A lacewing larva hides inside a dried leaf blade.

Green lacewing eggs can be purchased on a little strips of paper, which she hangs from the mangrove branches. When the eggs hatch, the larvae crawl out and, hopefully, go to town for the two to three weeks before they can fly. Once they earn their wings, each C. rufilabris loses its biting mouthparts and becomes a beautiful pollinator. IPMs are an important alternative to over-using chemicals that would kill the scale insects, but also kill invertebrates in the water. And, it is a great way to live blue!

an adult green lacewing
(Photo: Wikimedia Commons). An adult green lacewing.
An adult lacewing on a sign in the mangrove exhibit