Berberomeloe majalis (Linnaeus, 1758)
Red-Striped Oil Beetle
POLYPHAGA Emery, 1886
TENEBRIONOIDEA Latreille, 1802
MELOINAE Gyllenhal, 1810
LYTTINI Solier, 1851
Berberomeloe M. A. Bologna, 1989
Berberomeloe Bologna, 1988 is an Iberian-African genus long known to include least two species, the nomenclature has been confused in the past and several more species or subspecies have recently been added. The aptly-named Red-Striped Oil Beetle has long been known to vary in colour but entirely black specimens from the Sierra Nevada are now thought to constitute the new species B. tenebrosus, and more generally majalis has been split into six regional species based on molecular studies. The other well known species, B. insignis (Charpentier, 1818), long known as a synonym of the present species but morphologically distinct, is endemic to a narrow coastal region in south-eastern Spain. B. majalis is native to the western Mediterranean basin, occurring throughout most of Spain and Portugal, parts of Southern France and northern parts of Morocco, Tunisia and Algeria. Although widespread and locally common or even abundant, it has suffered a general decline over recent decades, especially in Europe; land development for housing, leisure and commercial greenhouses has drastically reduced or fragmented the scope of the habitat while wholesale use of pesticides, especially for crops grown intensively under glass or plastic, has severely damaged the wild bee population on which the beetles rely for their development. The species typically occurs on sandy or light soils with patchy vegetation including plenty of wild flowers, usually on open grassland or scrub but often in open woodland or orchards, especially near the coast. Adults are diurnal, they appear early in the year and gorge on foliage before mating, at this time males may be seen searching for females or following them persistently waiting for the chance to mate. After mating females search for suitable oviposition sites, usually in the vicinity of their host bees and usually on undisturbed areas. They lay numerous eggs in shallow depressions which they cover with soil before starting on another, this may continue for several weeks and each will produce many thousands of eggs. Triungulins emerge en masse and climb nearby flowers where they assemble, waiting for visiting host bees, but here the mortality is high as they will cling to any visiting insect and so many will fail to reach host nests and die-off. Once inside the nest they will leave their host bee and enter the larval cells, here they transform into immobile stages that will consume the host eggs, larva and pollen and nectar sustenance, and once the contents are consumed they will move to further cells until they are fully-grown. Pupation occurs inside the nest and adults emerge early the following year. Hosts are thought to include various solitary bees and other species are generally unsuitable as hosts e.g. if larvae enter honey bee hives they may attempt to feed but soon die-off. Adults are large and easily spotted as they walk vigorously across the ground, dragging their distended abdomens through loose soil and litter, they peak in abundance during May and June and, in season, mating pairs may be common as they tend to remain coupled for extended periods.
Adults vary widely in size but the majority are large, between 50 and 60 mm, they are absolutely distinctive due to the colour; entirely shiny black with a variable metallic-blue reflection and a bright orange or red band across the apical margin of the abdominal tergites. Head transverse (from above) and broader than the pronotum. Antennae unmodified; narrow with all but the diminutive second segment elongate. Pronotum broadest near obtuse anterior angles and narrowed to obtusely-rounded posterior angles, apical margin produced medially and basal margin recurved, surface unevenly convex, rugose and variably, though usually quite densely, punctured. Elytra overlapping at the base then widely separated, surface longitudinally rugose and finely punctured.