Hawaii is the most remote island chain on Earth. The vast majority of the islands’ insect life arrived through rare, chance colonization events over millions of years, followed by spectacular evolutionary diversification. However, the modern insect landscape is now dominated by species introduced through human commerce and travel. These introduced populations include household nuisances and devastating ecological threats.
How Isolation Shaped Hawaii’s Unique Insects
The native insect fauna of Hawaii is characterized by a high degree of endemism, meaning the species are found nowhere else in the world. An estimated 95% of the over 10,000 described native insect species are endemic, having evolved from only about 260 original colonizers. These initial successful arrivals, often a single pregnant female or a small group, led to “founder effects” where the new population carried only a fraction of the genetic diversity of the mainland source.
The most celebrated example of this phenomenon is the Hawaiian Drosophilidae, which underwent a massive adaptive radiation. A single ancestral species that arrived approximately 25 million years ago diversified into two lineages, Drosophila and Scaptomyza, comprising over 800 endemic species. This accounts for about one-third of the world’s entire Drosophila species. This explosion occurred as the flies specialized on various ecological niches, such as feeding on specific endemic plants or fungi, and adapting to the islands’ varying elevations and climates.
Other native insects also demonstrate this unique evolutionary history, including the endemic damselflies (Megalagrion) and the predatory caterpillars (Eupithecia species). The damselfly genus Megalagrion contains 23 endemic species, all descended from a single colonization event. The predatory caterpillars, which have evolved a unique sit-and-wait hunting strategy, illustrate how native lineages adapted to fill ecological roles that were often vacant due to the limited number of original colonizers.
Common Household and Tourist Nuisances
The most noticeable arthropods encountered by visitors and residents are typically non-native species that thrive in human-altered environments. The American cockroach, known for its large size and tendency to fly, is a common sight in kitchens and drains across the islands. Hawaii is home to at least 19 species of cockroaches, with the American, German, and brown-banded varieties being the most frequent nuisances in homes.
Termites are another significant domestic problem, causing over $100 million in property damage annually. The two most prominent introduced species are the Formosan subterranean termite and the West Indian drywood termite, both of which aggressively infest wooden structures. Mosquitoes, while a minor annoyance in other regions, are a major problem in Hawaii as vectors for diseases like dengue fever and the avian malaria that devastates native bird populations.
Invasive Species Causing Ecological Disruption
While many introduced species are mere nuisances, others are invasive species that pose severe threats to Hawaii’s fragile ecosystems and agriculture. The Little Fire Ant (Wasmannia auropunctata) is one of the most damaging invaders, forming dense colonies that deliver a painful, burning sting. These ants not only sting humans and pets but also blind animals and outcompete or prey upon native insects, disrupting entire forest food webs.
Other invasive arthropods target specific native plants or agricultural crops. The coconut rhinoceros beetle, a recent introduction, bores into the crowns of coconut palms and other tropical trees, weakening or killing them and threatening the islands’ iconic landscapes. Similarly, the coffee berry borer has caused major losses in Hawaii’s premium coffee industry. The introduction of invasive species continues at an alarming rate, with an estimated 20 new insects arriving each year.
Arthropods That Bite or Sting
For the average person, the most immediate physical threat comes from a handful of stinging or biting arthropods. The Hawaiian centipede (Scolopendra subspinipes) is the most feared, often reaching lengths of up to 12 inches. Its bite is highly venomous and intensely painful, sometimes requiring medical attention, though fatalities are extremely rare. These nocturnal, fast-moving centipedes are often found in damp areas or under debris.
A few species of spiders have also been introduced, including the Brown Widow and the Southern Black Widow. Several species of wasps and yellow jackets, such as the Western Yellow Jacket (Vespula pensylvanica), are also present. These stinging insects can be a threat when their nests are disturbed, and they pose a particular danger to native insects and spiders that they prey upon.