Earth Matters: A tale of introduced species

  • A Carolina mantis in South Carolina. CONTRIBUTED/JOSHUA ROSE

  • A mature Ailanthus altissimo (Tree of Heaven), location unknown. Geneva Wirth via Flickr

  • A spotted lanternfly in the Brooklyn Botanic Garden. The striking but problematic insect is incredibly destructive to trees and woody-stem plants. Rhododendrites/via Wikimedia

For the Gazette
Published: 11/12/2021 3:55:47 PM

This year, Massachusetts saw two species of insects arrive unbidden. One of them has been the subject of great attention, with warnings in advance, newspaper headlines about its arrival, and alerts from the state government. The other snuck in under the radar, barely noticed except by obsessive naturalists.

One is a potential menace that could cause millions of dollars’ worth of damage; the other is potentially beneficial, including eating the first. One is native to the U.S., historically occurring south of New Jersey; the other had never been seen on this continent before 2014, previously found no closer to here than Japan.

One feature that they share is that both can thank humanity for letting them reach Massachusetts.

The spotted lanternfly (Lycorma delicatula), when viewed in captivity or in its native range, is undeniably beautiful. Its forewings are gray tinted with pink or lavender, with bold black polka-dots on their forward two-thirds, while the remaining third features tiny, densely packed black rectangles separated by pinkish-gray lines in a pattern vaguely resembling a brick wall.

When this pair of wings is spread, it exposes hindwings which are brilliantly red, a shade reminiscent of a scarlet tanager, with more black polka-dots plus solid black and white patches. Its nymphs start out jet-black with bold white polka-dots, so different from their parents as to seem a separate species, but as they grow they develop red patches the same intense shade as the parents’ hindwings.

Unfortunately, the consequences of the lanternfly’s arrival are much less attractive than the insect itself. They feed on the sap of dozens of plant species, many of which we grow for fruit. They also attack trees that are important to forest ecology, including maples, cherries, poplars and birches. After being introduced to Korea, the bug wiped out entire grape vineyards and reduced other crops. As it feeds, it excretes “honeydew,” a sugary liquid; dense swarms of the bug rain down honeydew, producing rampant growths of sooty mold over anything beneath.

Long ago, we unknowingly paved the way for this invasion by introducing the lanternfly’s favorite plant. Ailanthus altissima, ironically known in English as “Tree of Heaven,” was once a popular landscaping tree but became one of the most pernicious invasive plant species in North America. Lanternfly populations feed and grow on Ailanthus, then spread onto native plants and commercial fruits.

Ailanthus secretes chemicals that make it inedible to most native insects, but the lanternfly absorbs and processes those chemicals into defenses of its own. The bug’s brilliant colors signal to predators that they will regret tasting the bug; only a few, including spiders, assassin bugs and yellow jackets, eat lanternflies without being repelled.

Carolina mantis

Coincidentally, one of the native predators most commonly observed eating lanternflies is also Massachusetts’ other new arrival. When Massachusetts was first settled, no praying mantises lived here. An Earth Matters column from 2018, “What color is your praying mantis?” noted that the only mantis species documented in our state were the Chinese and European mantises, both introduced decades ago. No native North American mantises lived here — until this year.

The Carolina mantis is a native of the southeastern U.S., but in recent years has spread beyond the south. Some references claim that the species was originally absent from New Jersey. It was unknown from New York before the 21st century. Volunteers for the iNaturalist citizen science project documented the first few Connecticut records in 2018.

Finally, in 2021, the first of its species discovered Massachusetts: The first was found in Hopkinton in September, followed by another in Manchester in October.

We know more about how the lanternfly reached Massachusetts than how the mantis did. The lanternfly lays eggs in a flat, gray case that blends in well against stone and concrete; the first ones to appear in the USA are thought to have arrived as eggs on a shipment of stone from China to Pennsylvania. The first one found in our state apparently hitched a ride here in a shipment of poinsettias. It took only seven years for the species to spread from Pennsylvania to Massachusetts.

The mantis has spread far more slowly, taking three years just to cross Connecticut. It, too, may have hitched rides on shipments of plants or other commerce — the Hopkinton record was found on a dumpster of a farm and nursery property — but the slow rate of its spread suggests that climate change is an influence, gradually allowing the mantis to survive incrementally farther north than it used to.

The three mantis species can be tricky to tell apart, or even to see, given their camouflage. Carolina is the smallest of the three. Like the other two, it can change colors, but apparently only when the nymph stages molt, so adults that reach maturity remain one color thereafter. It often has dark bands across its forelegs, and its wings frequently have a mottled, mosaic-like appearance, or sometimes a single black spot in the middle. The adult female’s wings are shorter than her abdomen, leaving her flightless.

Keep your eyes peeled for both the brightly colored spotted lanternfly and the far less conspicuous Carolina mantis around your neighborhoods. If you find a lanternfly, the Massachusetts Department of Agricultural Resources has an online form for submitting reports. No government agency is tracking the spread of the mantis, but posting photos on iNaturalist can help document their progress northward.

Joshua Rose is a naturalist who lives in Amherst. He is a Hitchcock Center member, a board member of the Hampshire Bird Club and a contributing editor of the website bugguide.net; he regularly leads programs for local nature-oriented groups. “What color is your praying mantis?” can be found at tinyurl.com/earthmatters-57.

Earth Matters has been a project of the Hitchcock Center for the Environment for 12 years. In response to the COVID-19 crisis, the Hitchcock Center adapted their programming and have sliding-scale fee structure for families facing financial challenges. To help the Hitchcock Center survive this difficult time, consider a donation at hitchcockcenter.org.
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