Jumping weevil (Rhynchaenus testaceus)
|Size||Length: 2.5 - 3.5 mm (2)|
Classified as Vulnerable in Great Britain (3).
This small jumping weevil, formerly known as Orchestes scutellaris (2), is reddish in colour, and has a long, elongated snout known as a 'rostrum' (4). It also has enlarged hind femora adapted to jumping (a characteristic of the genus) (2).
This weevil has always been scarce, but since 1940 it has been found only very sporadically, in east Cornwall in 1978, west Norfolk in 1987 and 1988, and Huntingdonshire in 1991 (3), 2001 and 2002 (2). Outside Britain it has a wide distribution, occurring in northern USA and southern Canada, and throughout much of Europe, reaching into Asia (3).
Inhabits wet woodland (5), where it is associated with alder (Alnus glutinosa) (3). It seems to prefer dried out, partially shaded alder carr habitat with sparse ground vegetation (2).
Very little is known of the ecology of the species, but it is known that the larvae live and feed inside alder leaves (3). Larvae produce short, serpentine leaf mines culminating abruptly in an enlarged leaf edge 'blotch'. When fully grown, larvae pupate in a rounded leaf edge cocoon. Adults have been found throughout the summer from May to September. It seems likely that they emerge in July and August and hibernate as adults. (This is known to be the case with the commoner closely related R. fagi). Other species of Rhynchaenus are known to produce sound by 'stridulation' in a similar way to grasshoppers; it is not known whether R. testaceus shares this characteristic (2).
The reasons for the scarcity of this weevil are unclear (3); it is possible that its preference for alder growing in unusually dry conditions is a limiting factor. Furthermore, the beetle is inconspicuous so it may well be under-recorded (2).
Listed under the UK Biodiversity Action Plan (UK BAP), the main aims for the conservation of this species are to maintain the current populations, with enhancement by the year 2010 and to establish populations at 6 sites within the former range before 2010 (3). Research into the weevil's biology and habitat preferences is currently being carried out at the University of Leeds, in order to inform conservation management recommendations (2).
For more on English Nature's Species Recovery Programme see:
Information authenticated by Jon Mellings (independent ecologist).
- Carr: term used to describe wet habitats. In East Anglia it is used to refer to wet woodlands, especially alder woods.
- Femora (or femur): in insects, the third segment in the leg, the largest segment of the leg in most adult insects. In tetrapods (vertebrates with four limbs) the upper bone of the hind limb.
- Hibernate: a winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.
- larvae: stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Pupate: the process of forming a pupa, the stage in an insect's development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
- National Biodiversity Network Species Dictionary (September 2002) http://www.nhm.ac.uk/nbn/
- Mellings, J. (2002) Pers. Comm.
- UK BAP (September 2002) http://www.ukbap.org.uk
- Personal observation from images
- English Nature. Species and habitat associations (September 2002) http://www.english-nature.org.uk/baps/species/overview.asp?Id=552&Habitat_Key=4&sType=C&PrevPage=habitat