What is a Longhorn Beetle?
Longhorn beetles belong to the family Cerambycidae (Order: Coleoptera). Many species have interesting patterns, colouration and are generally larger in size which makes many species easily recognisable in the field. Worldwide there are more than 30,000 species described to science, in Britain 69 are considered native or naturalised while many other species are recording as occasional imports. There are five species that are thought to be extinct in Britain (Lepturobosca virens, Strangalia attenuate, Cerambyx scopolii Füessly, Obrium cantharinum and Plagionotus arcuatus).
The following 4 subfamilies are present in Britain:
- Prioninae (1 species)
- Lepturinae (25 species)
- Spondylidinae (5 species)
- Cerambycinae (37 species)
Longhorn beetles, or cerambycids, can be recognised by a number of anatomical features.
- General appearance is generally elongate and robust
- Elytra can be brightly coloured or patterned
- Long antennae, sometimes longer than the beetle (musk beetle), although some have very short antennae (Rhagium spp.). Can be filiform or serrate.
- The feet (tarsi) have five segments but in most species the fourth segment is hidden.
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Most longhorn larvae are wood-borers of deciduous and coniferous wood. A small number of species like Phytoecia and Agapanthia are phytophagous feeding on plant material of herbaceous plants. One unusual form of development occurs in the genus Pseudovadonia where the larvae develop in fungal mycelia within the soil. Adults of non-native species are regularly found after emerging from imported timber products, sometimes many years after they have been imported.
The life cycle begins with the female beetle laying eggs in rotting fungus, living or deadwood. Once the eggs hatch, the larvae begin feeding upon their food source. The length of time spent in the larval stage varies among species but this time can range from months to years. Once the larvae reach a suitable stage in their development they begin to pupate and then after pupation is finished they emerge as adult beetles. Adults are often found on flowers or on recently-fallen or felled timber. Some species such as the House longhorn Hylotrupes bajulus can be considered as a pest in houses by developing in structural timbers. However, Longhorns are also of great ecological importance in many ecosystems, many species provide an invaluable pollination service and the larvae eat decaying matter, in turn recycling nutrients through the ecosystem.
How to find longhorn beetles
Adult longhorn beetles are easier to find, and detection methods are much less destructive on the habitat. Longhorn beetles begin to emerge from April to August, although some species can be found as early as March and as late as September. A few species can be found all year round as adults, for example Rhagium species. Collecting with a sweep net or beating tray is a very useful method of collecting. The adult beetles can be found feeding on flowers with Hawthorn, Dogwood Hogweed and many Umbellifers being fantastic host plants.