Bioacoustics of Sphingonotus (Sphingonotus) insularis

Remarks . This species was described as Wernerella insularis , but I provisionally placed it in Sphingonotus Fieber, 1852 for the reasons reported below. Wernerella Karny, 1907 was erected for Thalpomena picteti Krauss, 1892 from Tenerife, and included 10 Canarian and African species, characterized by a rugose pronotum with lateral carinae in the metazona. Hochkirch and Husemann (2008) , on genetical and morphological bases, established that the Canarian type species of the genus actually belongs to Sphingonotus . However, the Socotran species, as well as some African species (cf. Johnsen 1985 ), have characteristics well different from other Sphingonotus and cannot be classified within this genus. A more extensive study of African related genera and other species formerly included in Wernerella is needed before to establish a new genus for them. Here, I report characters which consent to easily separate it from Sphingonotus . Tegmina are short, wings are large and the general aspect is stout. Mesosternal and metasternal interspaces are very large, ca. 2 times larger than long the former and 3 times the latter ( Figs. 17-19 ). All margins of the pronotum are undulated, the upper carina of hind femora is also undulated and shows a sudden drop in height, proximal to the narrowing part. Upper inner area of hind knees is provided with many setae and the corresponding area of tegmina is covered by microscopic “pearls”, as those recorded by Johnsen (1985) for Wernerella somalica Johnsen, 1985 . I observed that Socotra specimens, as supposed by Johnsen (1985) for W. somalica , when start to fly, emit a peculiar song, produced by the pair setae/“pearls”.

Bioacoustics. In the available recordings, two elements can be recognised, which possibly represent both courtship and rivalry. The first element exists of repeated echemes of 3 (2–5) loosely grouped syllables (Fig. 98 ). Syllables last about 18–20 ms and the syllable repetition rate within these echemes is about six per second. A clear up and downstroke within a syllable is visible in the oscillogram. The first element has a peak frequency of 3–4 kHz. The second element is formed by an echeme with 13–21 syllables (Fig. 99 ). The syllable duration is about 4 ms and syllables are repeated at the rate of about five per second. This echeme has a broader frequency spectrum and seems to be produced by wing flapping, but the latter needs to be confirmed. Massa (2009) observed specimens producing a sound before taking off. This may refer to the latter sound element.