''Hylobius transversovittatus'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

weevil Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small – less than in length – and herbivorous. Approximately 97,000 species of weevils are known. They belong to several fa ...

in the family

Curculionidae The Curculionidae are a family of weevils, commonly called snout beetles or true weevils. They are one of the largest animal families with 6,800 genera and 83,000 species described worldwide. They are the sister group to the family Brentidae. Th ...

. It is native to the

Old World The "Old World" () is a term for Afro-Eurasia coined by Europeans after 1493, when they became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia in the Eastern Hemisphere, previously ...

where both adults and larvae feed on purple loosestrife (''

Lythrum salicaria ''Lythrum salicaria'' or purple loosestrifeFlora of NW Europe''Lythrum salicaria'' is a flowering plant belonging to the family Lythraceae. It should not be confused with other plants sharing the name loosestrife that are members of the family Pr ...

''). This plant is regarded as an

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

in North America and the weevil has been introduced into both the United States and Canada in an effort to control the plant.

Description

The adult ''Hylobius transversovittatus'' is a dark brown colour with two irregular transverse lines of tufts of white hair. It is about thirteen millimetres long and six millimetres wide and has a narrow head and thorax and a curved trunk-like

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

. The antennae are elbowed and the legs reddish. The

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

are white or pale yellow and oval in shape and hatch within about two weeks. The

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e are a creamy colour with dark brown heads and adopt a crescent shape.

Biology

Adult ''Hylobius transversovittatus'' beetles emerge in the spring from the soil or leaf litter where they have been overwintering. They feed on the leaves of purple loosestrife (''

'') and are mostly nocturnal. Their presence is evidenced by the ragged edges to leaves caused by their chewing. They are most active from June to August and may live for several years. The females lay about 200 eggs over a period of two to three months with each being deposited singly near the roots of purple loosestrife or occasionally on the stem. On hatching, the soil-laid larvae feed on

root hair Soil biology Root hairs or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of ...

s before burrowing their way into the root where they feed on tissue within the woody rootstock. Stem-laid larvae tunnel into the stem and work their way down to the root. Larval development may be interrupted by periods of flooding and resume when the water level falls. The larvae undergo two moults over a period of one to two years before forming pupation chambers in the upper part of the root. They then moult again and become

pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

e. When metamorphosis is complete, the adult beetles chew their way out, usually emerging between July and October. The weevils can overwinter in any of their life stages, as eggs, larvae, pupae or adults.

Host species

''Hylobius transversovittatus'' seems to be host-specific to purple loosestrife ''(Lythrum salicaria)''. Before it was introduced into North America the weevil was tested on about fifty plants native to the continent to see whether they were susceptible to attack. Of these, only swamp loosestrife ('' Decodon verticillatus'') and winged loosestrife (''

Lythrum alatum ''Lythrum alatum'', commonly known as winged loosestrife, winged lythrum or (in Britain and Ireland) angled purple-loosestrife, is a species of flowering plant belonging to the family Lythraceae. It is endemic to wetland areas in central and east ...

'') were found to be potential hosts. It was found however that if purple loosestrife was available, it was preferred over these native species and the weevil was considered not to be a threat to non-target plants.

Use in biological control

Purple loosestrife is a native of Europe, Asia, northwest Africa and parts of Australia. In these countries a number of insects are associated with it. These include ''Hylobius transversovittatus'', the adults of which eat the foliage and the larvae of which tunnel through and eat the root. When purple loosestrife was introduced into North America these insects were not available to keep it under control and it became rampant. It is now found in large stands throughout the northeastern United States, southeastern Canada and the American Midwest where it crowds out other species and is a threat to

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

. The weevils and their eggs were introduced to test sites in Virginia from 1992 onwards. They became successfully established and six years after the introduction, 28% of the roots of purple loosestrife plants were found to be infested. Larvae were also detected in roots four hundred metres downstream from the release point. Although the feeding of the adult weevils does little damage to the plant, the activities of the larvae, especially if there are several in one rootstock, weaken the plant, make it more susceptible to stressful conditions and reduce the quantity of seed produced.Wilson, L. M., Schwarzlaender, M., Blossey, B., & Randall, C. B. (2004). ''Biology and Biological Control of Purple Loosestrife.'' Morgantown, WV: USDA Forest Health Technology Enterprise Team.

References

{{Taxonbar, from=Q147484 Molytinae Beetles of Europe Insects used for control of invasive plants Biological pest control beetles Beetles described in 1777 Taxa named by Johann August Ephraim Goeze