New research, bolstered by contributions from citizen scientists, has uncovered an astonishing characteristic of the meadow spittlebug—its ability to feed on a staggering 1,300 species of host plants, more than double the range of any other known insect. This discovery, published today in the journal PLOS ONE, holds significant implications for efforts to combat the spread of a bacterium responsible for widespread crop damage, affecting olive trees in Italy, grapevines in California, citrus trees in South America, and almond trees in Spain.
Lead author of the study, Vinton Thompson, a research associate in the Museum’s Division of Invertebrate Zoology, describes the findings as a “sobering wake-up call,” highlighting the 1,300 host plants as 1,300 opportunities for the transmission of pathogenic bacteria in both natural and agricultural settings.
The meadow spittlebug, also known as the froghopper (Philaenus spumarius), sustains itself by extracting sap from plants using straw-like mouthparts, inadvertently picking up bacteria in the process. These insects have been recently identified as vectors for the bacterium Xylella fastidiosa, responsible for the destruction of olive groves in Italy’s Apulia region.
To better predict which plant species and ecosystems are at risk from this vector, researchers needed a comprehensive understanding of its host range. Thompson, who has devoted five decades to studying and documenting spittlebugs’ host plants, collaborated with fellow scientists in the United Kingdom to achieve this goal.
The study drew upon data from published literature, host records linked to museum specimens, direct observations, and insights from a citizen science initiative called BRIGIT, conducted in Britain from 2019 to 2021. BRIGIT aimed to prepare for the possible introduction of X. fastidiosa to the UK.
The meadow spittlebug boasts a vast geographic distribution and can thrive in diverse climates, ranging from Hawaii to regions just south of the Arctic Circle. While scientists have long suspected that this insect had an extensive host range, the newly calculated number is startling: the meadow spittlebug feeds on over 1,300 plant species, spanning 117 different plant families, setting a world record for insects.
These host plants encompass a broad spectrum, including ferns, herbs, shrubs, vines, trees, annuals, perennials, grasses, and forbs, adapting to tropical, subtropical, temperate, and boreal zones, as well as conifers. Notably, the insect with the second-highest number of plant hosts is the fall webworm, a moth known to feed on 636 plant species.
Claire Harkin, a study author from the University of Sussex, remarks, “The spittlebug is the ultimate herbivore champion,” as it will feed on nearly all types of vascular plants except those submerged in aquatic environments.
The primary reason behind the meadow spittlebug’s vast host range remains the subject of further research. Nonetheless, scientists suspect that its preference for xylem sap, which carries water within the plant, as opposed to the more specialized phloem sap favored by other sap-eating insects, contributes to this adaptability. Xylem sap shares a consistent composition across a wide range of host plants.
“These bugs feed on almost anything they can reach with their mouthparts,” notes Thompson. “Unfortunately, this means there’s tremendous potential for the spread of X. fastidiosa in natural ecosystems if it’s introduced. This review is just the first step in thinking about how to control this bug and the diseases it spreads.”
The meadow spittlebug’s remarkable characteristics extend beyond its diverse diet, including its unmatched jumping ability concerning body size, the highest measured sucking power among all bugs, and the prodigious daily equivalent of human urine excretion—a testament to nature’s diversity and adaptability.