Chorthippus biguttulus grupo

JOURNAL OF NATURAL HISTORY, 1988, 22, 897-929

The songs and taxonomy of the grasshoppers of the Chorthippus biguttulus group in the Iberian Peninsula (Orthoptera: Acrididae)
D. R. R A G G E and W. J. R E Y N O L D S

British Museum (Natural History), Cromwell Road, London SW7 5BD, UK (Acceptedl8March 1988)
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TheChorthippus biguttulus group includes a number of common European species that are difficult to distinguish morphologically but are easily recognized in the field by the distinctive calling songs of the males. These song-patterns have not previously been studied in Spain and as a result the Iberian members of the group have been misidentified in almost all the extensive Spanish literature on theecology and cytogenetics of these insects. In this study the male calling songs of all six members of the group known from the Iberian Peninsula and North Africa are fully described and illustrated with oscillograms at several different speeds. The songs of the three species known only from Iberia or North Africa, jacobsi, yersini and marocanus, are fully described for the first time (marocanus ishere raised in rank from subspecies). Notes on recognition, using both morphology and song, are given for each species, and two identification keys are provided, one based on morphology and the other on song. It is shown that the three species biguttulus, brunneus and mollis, previously believed to be widespread in Iberia, are absent from most of the peninsula. KEYWORDS:acoustics, Acrididae,Chorthippus, grasshopper, Iberia, North Africa, Orthoptera, song, taxonomy.

Introduction

Chorthippus biguttulus belongs to the Gomphocerinae, a group that includes most of the European grasshoppers of open grassland and moorland. It was the first-named member of a complex of closely similar species referred to for convenience as the biguttulus-group and characterized by their slit-like tympana,angled pronotal lateral carinae, fully developed wings and lack o f any striking features ofcolour pattern. Until recently this group was thought to consist o f only three c o m m o n species, C. biguttulus (L.), C. brunneus (Thunberg) and C. mollis (Charpentier), difficult to distinguish morphologically but easily recognized in the field from the highly distinctive calling songs of the males.However, it has now become clear, mainly through studies on the songs, that the group contains at least twice this number of species in western Europe alone (Ragge, 1987) and several more in eastern Europe and Asia. All these species are closely similar in morphology and frequently misidentified. As these grasshoppers are often used in ecological and cytogenetic studies, and are sometimes pests in themore eastern parts of their range, an urgent need has arisen for a reliable guide to their identification. The aim of this paper is to provide such a guide for the Iberian Peninsula. Until 1972 the biguttulus-group was thought to be represented in the Iberian Peninsula by only two members, biguttulus and brunneus, both of which were believed

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D.R. Ragge and W. J. Reynolds

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to be common and widespread (Morales, 1942). Then Harz (1972:130) published the first record ofmollis from Spain (near Barcelona) and at the same time described what he believed to be a new subspecies mollis reissingeri from near Alicante. Soon afterwards he described a further member of the group,jacobsi (which he had detected largelyby its song), and a new subspecies biguttulus yersini, both from a number of Spanish localities (Harz, 1975a: 890, 895). Finally, Presa (1978a: 78) described the new subspecies biguttulus montanus (later corrected to b. hispanicus) from the Sierra de Guadarrama. During the past 20 years one or other of these taxa has featured in numerous ecological, biogeographical and cytogenetic studies on...