Isochnus sequensi
This record describes Isochnus sequensi (species). Recorded family: Curculionidae. Recorded order: Coleoptera.
Identification and Appearance

A tiny (2.0-2.5mm) black weevil with a white scutellum, pale tarsi and tibiae and yellow/red fore and mid femora. The antennal funiculus is six-segmented. The larvae feed on willow leaves, forming brown blotch mines. The adult must be reared out to identify the mine Mines are indistinguishable from the very similar but rarer Isochnus foliorum . Adults must be collected or reared to confirm identification. I. foliorum has pitchy fore and mid femora and seven segments in the antennal funiculus. To rear the adults a leaf or two containing mines should be collected and kept in a tupperware box with a little damp kitchen-towel wrapped around the stem to keep the leaf green. This should be kept in a cool dark place and checked every day for adults and wiped clean to avoid mold. The adults will usually emerge after several days. To differentiate between species :- The front and mid femora of I. sequensi are red to yellow. The front and mid femora of I. foliorum are black to pitchy. Not identifiable from the mine. Adults must be collected/reared. Unless identified by a recognised expert, photographic evidence is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used. Note the beetle's size and describe the identifying characters. It is advisable to retain the specimen in case further checks are needed. The larvae produce blotch mines in the leaves of Salix species, and sometimes Populus. The adults are usually found close by. The preferred species in Britain appears to be hybrid crack-willow, S. x fragilis .
Classification
- Kingdom
- Animalia
- Phylum
- Arthropoda
- Class
- Insecta
- Order
- Coleoptera (Beetles)
- Suborder
- Polyphaga
- Superfamily
- Curculionoidea
- Family
- Curculionidae (Snout and Bark Beetles)
- Subfamily
- Curculioninae
- Tribe
- Rhamphini
- Genus
- Isochnus
Imported taxonomy record. Source availability varies; see the source references and editorial policy below.
Habitat and Range
Habitat
The larvae produce blotch mines in the leaves of Salix species, and sometimes Populus. The adults are usually found close by. The preferred species in Britain appears to be hybrid crack-willow,
Seasonal Activity
Mines can be found when the hosts are in leaf.
Diet and Behavior
Life History
The larvae feed within a blotch mine and then pupate within the mine.
Additional species information
Recorded status
The species had been considered local and scarce but is spreading and increasing from its strongholds in south-eastern England. It can be abundant where it occurs.
About Primitive Winged Insects: the wider group
Order-level background for Coleoptera, the group containing Isochnus sequensi. Species-specific details appear above.
Group overview
Coleoptera is the largest order of insects with over 400,000 described species, representing ~25% of all known animal species and ~40% of all insects. In the U.S. alone, nearly 30,000 beetle species have been identified.
Ecological role of the group
Beetles are prominent decomposers, especially in forests, breaking down dead wood and recycling nutrients. As predators, they reduce populations of pest insects. Many species are also important pollinators of flowering plants.
Economic and practical significance of the group
Beetles have major economic significance: leaf beetles (Chrysomelidae) and weevils (Curculionoidea) are among the most destructive agricultural pests globally, costing billions annually, while predatory species like ladybugs provide natural pest control.
Recorded sources for this group: Britannica, Smithsonian, NCSU Entomology. Imported estimates may describe particular regions or reporting periods.
Photos of Isochnus sequensi (10)
Frequently Asked Questions About Isochnus sequensi
What is Isochnus sequensi?
Isochnus sequensi is a species in the family Curculionidae, within the order Coleoptera.
Where is Isochnus sequensi found?
Habitat: The larvae produce blotch mines in the leaves of Salix species, and sometimes Populus. The adults are usually found close by. The preferred species in Britain appears to be hybrid crack-willow,
When is Isochnus sequensi active?
Isochnus sequensi: seasonal activity - Mines can be found when the hosts are in leaf..
What is the life cycle of a Isochnus sequensi?
The larvae feed within a blotch mine and then pupate within the mine.
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