Invaders TitleNYSM home
R.Gordon, 1985. The Coccinelidae (Coleoptera) of America North of Mexico. J. N.Y. Ent. Soc. 93:1-912.

The Nine-spotted Ladybug used to be one of the most commonly encountered ladybugs throughout its historic range (shaded area). In recent years, it has declined to the point which it is now only infrequently encountered.


Humans have a long history of introducing non-native species they think are beneficial.
They might introduce them to control weeds and pests, to provide game, or for nostalgia. Humans also have an equally long history of not fully appreciating or understanding the consequences of these introductions.

An example is how the Seven-spotted Ladybug affected the native Nine-spotted Ladybug. The Nine-spotted Ladybug was the most common ladybug in New York state until the 1940s. Then its population rapidly dropped. This was likely caused by the introduction of the closely related Seven-spotted Ladybug. The Nine-spotted Ladybug is the official New York state insect. Yet, it has not been collected in the state in recent decades. Over 100 species of ladybugs have been intentionally introduced to North America. Almost all ladybug species are predators of aphids, so they are given the label “beneficial.” Many native ladybug species, however, are in decline. This is thought to be the result of these introductions.
Honey Bee
© 2006 Joyce Gross


Apis mellifera
The Honey Bee is native to Europe, the Middle East, and Africa. It was introduced by colonists for honey production starting in 1622. Today, it is valued as a pollinator for many agricultural crops and for honey production. Colonists of North America cleared, altered, and degraded land. Native species were harvested and many non-native species were introduced. At that time, there were many native bees that served as pollinators of native plants. There is little documentation of the effects these changes had on existing native pollinators and other native species as well. We will never really know how many native species were affected by the Honey Bee.

Today, the Honey Bee is uniquely beneficial to humans. It is the most important managed crop pollinator throughout most of the world. The recent concern about reductions in Honey Bee numbers, as a result of parasitic mites and Colony Collapse Disorder, is a major concern that scientists are trying to unravel.
Tachinid Fly
Kevin D. Arvin,

Tachinid Fly

Compsilura concinnata
This fly is native to Europe and was released in 1906 to control the Gypsy Moth. Their maggots are parasitic. The fly deposits a maggot directly into the host larva, killing it within seven days. Unfortunately, the fly has also been implicated in the decline of native eastern species of silk moths. It is also known to parasitize 200 alternate native species, including beetles, bees, and moths.
gypsy moth


Gypsy Moth

Lymantria dispar dispar
Gypsy Moth is native to Europe. In 1869, an amateur entomologist introduced them in Massachussets. He thought their cocoons could be used to develop a silk resource outside of China. This was not so, and by 1898 the Gypsy Moth had become a major pest in the United States. Their larvae feed on an estimated 300 to 500 species of potential plant hosts! Repeated defoliation stresses and can kill trees.

Female Gypsy Moths cannot fly. It spreads mostly by humans moving vehicles or equipment with egg masses laid on them to other areas. Egg masses may contain 100 to 1,500 eggs.

Caterpillars disperse short distances through ballooning, riding in the wind on strands of silk.
Peter K. Ducey, SUNY Cortland

Earthworms: Friend or Foe?

Red Worm, Trout Worm (Lumbricus rubellus)
Nightcrawler (Lumbricus terrestris)
Octagonal-tail Worm (Dendrobaena octaedra)
Crazy Worms, Jumpers (Amynthas sp.)

Many introduced species have been around so long, people believe they are native. Glaciers from the last ice age wiped out earthworms in parts of North America. Earthworms are suspected to have come to North America over the last 500 years from Europe and Asia. They have several means of introduction and spread. They may have been transported accidentally in soil with plants and in ship ballast.

They can also be intentionally introduced to assist agriculture and composting, or for bait. Earthworms break down leaf litter, recycle soil nutrients, and create soil burrows. Good for gardens and agriculture, these same activities can be harmful in native forests and fields. Earthworms may alter forest floor soil habitats by eating too much leaf litter. This might change which plants and animals can live in these areas.

broadhead planarian
Peter K. Ducey, SUNY Cortland

An Invasive Earthworm Predator: Broadhead Planarian

Bipalium adventitium
Wandering Broadhead Planarian is native to Asia. It was probably introduced accidentally to North America in the early 1900s in soil of horticultural plants. This soil flatworm is now found across the northern United States. These planarians are aggressive predators of earthworms, attacking and killing earthworms many times their own size. Scientists are investigating whether the flatworms eat enough earthworms to change the sizes of earthworm populations..
Scott Bauer, USDA

Multi-spotted Asian Ladybug

Harmonia axyridis
The Multi-spotted Asian Ladybug is native to Asia. It was first introduced to the United States in 1916. Over the years, it has been repeatedly introduced to control aphids. Because of its large populations, the Multi-spotted Asian Ladybug is implicated in the decline of native ladybugs across the United States.

The Multi-spotted Asian Ladybug overwinters indoors and is considered a nuisance. It can gather by the hundreds, staining walls and ceilings. In western New York, the adults are known to nibble on grapes, probably for the water content. It will occasionally bite people.