The praying mantis, with its distinctive posture and predatory front legs, is a recognizable insect found across many of Oregon’s landscapes. Many people assume this creature is a natural part of the local ecosystem, often welcoming it into their gardens. However, the presence of these efficient hunters in the Pacific Northwest is a complex issue, as the most commonly sighted species are not native to the region. Understanding the distinction between native and introduced species is important for the state’s ecological dynamics.
The Status of Praying Mantises in Oregon
The vast majority of praying mantises observed in Oregon are non-native species that have become well-established. The two most widespread are the Chinese Mantis (Tenodera sinensis) and the European Mantis (Mantis religiosa). The Chinese Mantis was first introduced accidentally to the eastern United States in 1896, likely arriving with nursery plants. Its egg cases have since been widely distributed across the country.
The European Mantis was introduced to the U.S. in the late 19th century and later released in the Northwest for biological pest control. Both species have proven highly adaptable to Oregon’s climate, successfully outcompeting smaller, native insects. Their prevalence is largely due to the commercial sale of their egg cases (oothecae), which consumers purchase for garden pest control.
Oregon does host at least one native species, the California Mantis (Stagmomantis californica), and a native genus of ground mantis (Litaneutria). Sightings of these native species are extremely rare and highly localized, often confined to the warmer, drier areas of southern or eastern Oregon. Most encounters in urban and agricultural areas involve the dominant, introduced populations.
Identifying Oregon’s Most Common Species
Distinguishing between the two most common species in Oregon involves observing size and distinct markings. The Chinese Mantis is the largest mantis species in North America, reaching lengths of up to five inches as an adult. Its coloration is variable, appearing in shades of pale green or tan, and its wings typically extend past the tip of its abdomen.
A key identification feature of the Chinese Mantis is a bold green stripe that runs along the outer edge of its forewings. This species also often displays a vertically striped pattern on its face. The European Mantis, by contrast, is noticeably smaller, generally reaching a maximum length of three to four inches.
The most reliable way to identify the European Mantis is by the characteristic black or dark brown spot located on the inner side of each foreleg, near the body. This marking sometimes has a pale center, resembling a bullseye. The European Mantis is often a bright, uniform green, though it can also be tan or brown.
Ecological Role in Local Habitats
Praying mantises are ambush predators; they sit and wait for prey to come within striking distance. This feeding strategy, combined with their generalist diet, defines their impact on Oregon’s habitats. They are highly indiscriminate eaters, consuming nearly any insect they can subdue, regardless of whether it is considered a pest or a beneficial species.
The large, non-native mantises significantly affect local biodiversity by preying on native pollinators, such as bees and butterflies. They also consume beneficial insects, including native lady beetles and lacewings, which naturally control garden pests. This lack of selectivity undermines the perception that they are purely beneficial for pest management.
Adult female Chinese Mantises, due to their size, have been documented attacking and eating small vertebrates. These prey include lizards, frogs, and even small hummingbirds. The introduction of these large, non-native predators adds pressure to native insect and small animal populations. Their aggressive nature allows them to thrive and potentially outcompete the smaller, rarer native mantis species for food resources.