POLYPHAGA Emery, 1886

CUCUJOIDEA Latreille, 1802

Byturus Latreille, 1796

B. ochraceus (Scriba, 1790) 

B. tomentosus (De Geer, 1774) 

3.2-4.6mm

BYTURIDAE Gistel, 1848

Raspberry Beetles

Two widespread and common species which should soon be found by sweeping a variety of flowers. 

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Introduction

This small family is divided into two subfamilies; Byturinae Jacquelin du Val, 1858, with about 25 species which is Holarctic, and Platydascillinae Pic, 1914, with species in Southeast Asia. Three species of Byturinae in 2 genera occur in Europe; the widespread Byturus tomentosus (DeGeer, 1774) and B. ochraceus (Scriba, 1790), and the rare Xerasca meschiggi (Reitter, 1905). Xerasca is superficially similar to Byturus but with uneven pubescence and a patterned elytral colouration giving the species a mottled appearance. Byturus urbanus (Lindeman, 1865), a widespread pest of soft fruits in the U.S.A., may be conspecific with B. tomentosus .Both European species of Byturus occur in the U.K. Byturus tomentosus is generally common throughout England and Wales and there are records scattered through Scotland and Northern Ireland. B. ochraceus is the more local species, occurring through England north to north Yorkshire but appears to be absent from the West Country and most of Wales. Both species are abundant throughout South Hertfordshire, West Middlesex and South Buckinghamshire.

The larvae of Byturus generally feed in the base of the developing fruit, and as the eggs are laid during early summer those fruits forming later in the year may be unaffected. On a commercial scale earlier fruits can be destroyed by raspberry beetle and the recommended method of control is applying insecticides when the first fruits appear in early summer, this involves spraying with broad-spectrum insecticides like pyrethrum and synthetic pyrethroids such as deltamethrin or cyhalothrin. Water traps are also employed using karimone lures; these attract both sexes and are much less environmentally destructive although they also attract other insects involved with cane-fruits.

UK Species

Our two species of Byturus are of very characteristic appearance; 3-5mm. elongate, pale to dark brown or grey (juveniles are lighter) and densely pubescent. The head is produced in front of the eyes and the mandibles are prominent and sharp. Eyes circular or nearly so, large and protruding. Antennae inserted in front of the eyes; 11-segmented with a 3-segmented club. Segments 1 and 2 are longer and broader than 3-6. Pronotum transverse and convex, with explanate side margins. Evenly rounded or sinuate towards right angled hind angles. Hind margin sinuate, appearing straight from above. Elytra parallel-sided or widened towards the rear, more so in females, and smoothly rounded at apex. Humeral prominence and side margins well developed. With large and small punctures, lacking striae but the pubescence will often be seen matted in the field and this may give the impression of striae. Tibiae smooth, with a small spur on the inner apical angle. Tarsi 5-5-5 Segments 1 and 4 small, 2 and 3 strongly bilobed. Last segment as long as others combined. Each claw with a large basal tooth. Females are overall broader than males.

Although superficially similar there are sufficient differences in morphology to avoid the need for dissection. In doubtful cases, which will be unlikely with a little experience of such common species, the aedeagi are distinctive; in tomentosus it is smoothly lanceolate whereas in ochraceus it is constricted before the apex.      

Byturus ochraceus (Scriba, 1790)

-Generally larger, 4-4.6mm.

​-Elytra more parallel​ sided.

-Pronotum distinctly more   convex.

-Elytral margin only visible behind the humerus.

-Eyes much larger - longitudinal

 diameter is clearly greater than

 half the width of the frons.

-Punctures smaller, more   randomly placed.

 
Byturus tomentosus (De Geer, 1774) 

-Generally smaller, 3.2-4mm.

​-Elytra generally widened   towards apex.

-Pronotum distinctly less   convex. explanate margin   broader towards the base but   a little narrower towards the   front angles

-Elytral margin generally visible from above.

-Eyes much smaller - longitudinal diameter less than half width of frons.

-Punctures larger and loosely   arranged on rows.

Byturus ochraceus is strongly associated with Geum urbanum (wood avens or herb Bennet). When full grown the larvae descend the stems and burrow some 5cm into the ground to construct a pupal chamber. Pupation occurs during July and August, and adults eclose during August and September but remain in the ground until the following spring. They are good fliers and active during warm days in late April.

Byturus tomentosus is the Raspberry Beetle, also widespread through central and northern Europe, and in some years can be a serious pest in commercial soft fruit production. Adults appear early in the year; April to May depending on latitude etc. and are common until July. Locally we find occasional specimens through to September. Adults emerge from the soil and visit flowers, locally they are abundant on Crataegus and Ranunculus spp. but they occur on a wide range of flowers at this time. The adults can cause damage at this time by feeding on blossom, buds or new leaves of host plants. They rarely do serious damage unless numbers are large in which case significant losses through malformed or poorly developed fruits may result. Females are attracted by the scent and colour of host flowers, feeding on them and laying eggs. Larvae feed on ripening fruits and sometimes damage the stems and shoot tips. They burrow into the fruits to feed at the base and usually go undetected until the fruit is harvested. Affected berries become shrivelled, distorted and hard.

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