MELOIDAE Gyllenhal, 1810

Oil Beetles

These large, distinctive beetles are sometimes encountered on the ground or among grass etc. in bright sunshine. All species are very local.

POLYPHAGA Emery, 1886 

TENEBRIONOIDEA Latreille, 1802

2

3

10

8-40mm

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Introduction

This is a large family of about 3000 species in 120 genera and 4 subfamilies, they are distributed worldwide with the exception of New Zealand and most of the Polynesian islands and the greatest diversity is in open and arid tropical, subtropical and steppe regions; about 50 genera occur in the New World of which 22 are Nearctic, and of the 80 or so Old world genera 53 are Palaearctic, 40 are Afrotropical, and 22 are Oriental while only 7 occur in Australia. The European fauna includes 210 species although only 19 occur in central regions and 10 extend to the UK. Several genera include well-known or notorious species and there are many agricultural pest species but much of the family, especially in Old World regions, is in need of revision.  Of the 4 subfamilies only one is of restricted distribution;

  • Eleticinae Wellman, 1910 includes 4 tribes and is restricted to South America, Africa, India and Southeast Asia. Derideini Wellman, 1910 includes 4 genera, 3 of which, including the large genus Iselma Haag-Rutenberg, 1879, are restricted to Africa while the 3 species of Anthicoxenus Fairmaire & Germain, 1860 are endemic to Chile. Eleticini Welman, 1910 includes 3 genera, 2 of which are monotypic and Neotropical; Serrospasta Selander, 1966 is endemic to Colombia and Eospasta Selander, 1966 is endemic to Chile. The remaining genus, Eletica Dejean, 1834 is restricted to central and southern Africa, it includes >70 species and is most diverse in the Congo. Morphozonitini Kaszab, 1969 includes 4 small genera and is restricted to central and southern Africa. Spasticini Kaszab, 1959 includes 3 Neotropical genera.

  • Nemognathinae Laporte, 1840 includes 2 tribes and about 10 genera and occurs mostly in warmer areas worldwide. Horiini Latreille, 1802 includes 3 genera and is pan-tropical with the greatest diversity in Africa. Nemognathini Laporte, 1840 is dominated by a few large and very widespread genera e.g. Nemognatha Illiger, 1807 (80 spp.) and Zonitis Fabricius, 1775 (>160 spp.) but some are more restricted e.g. Palaestrida White, 1846 and Palaestra Laporte, 1840 are Australian, Apalus Fabricius, 1775 is an Old World, mostly African genus, and Gnathium Kirby, 1818 is a New World, mostly Nearctic genus. The 18 species of Sitaris Latreille, 1802 are Palaearctic, most are of restricted distribution in warmer areas of Europe and northwest Africa but the very widespread S. muralis (Forster, 1771) extends north and is established in the UK. The monotypic Allendesalazaria Escalera, 1910 is endemic to Morocco and Algeria.

  • Tetraonycinae Boving & Craighead, 1931 includes 3 genera, of which 2 are probably monotypic, and is primarily Neotropical; only 5 species of the large genus Tetraonyx Latreille, 1805, which includes >100 species, occur in North America.

  • Meloinae Gyllenhal, 1810 is by far the largest subfamily, it is divided into various tribes but the group is very widespread, diverse and poorly understood and so various systems will be found in the literature but the following tribes are variously recognized.

    • Cerocomini Leach, 1815 includes 6 genera which, with the exception of the single small genus Somalarthrocera Turco & Bologna, 2008 from Kenya and Somalia, is distributed around the Mediterranean; the largest genus Cerocoma Geoffroy, 1762 includes 30 species, 13 of which occur in Europe. None occur in the UK.

    • Epicautini Denier, 1935 comprises about 6 mostly large and very widespread genera although 2 are more restricted; Denierella Kaszab, 1952 includes 11 species from southern Asia, and Linsleya MacSwain, 1951 includes 6 Nearctic species. The genus Epicauta Dejean, 1834 is among the largest of the family with >400 species and occurs in warmer regions worldwide, almost half the species occur in the New World. Cyanoelytra Paringuey, 1909 includes about 40 species and is largely restricted to Africa with a couple occurring in southern Asia. Psalydolytta Paringuey, 1909 is a large (>60 spp.), mostly African genus with a few species occurring in India.

    • Eupomphini LeConte, 1862 includes about 30 species in 7 genera and is restricted to the Nearctic region.

    • Lyttini Solier in Gay, 1851 is a very large worldwide group of more than 30 genera. A single very widespread species of the large genus Lytta Fabricius, 1775 occurs in the UK, this is otherwise a worldwide group of about 110 species of which about 70 are Nearctic. By far the greatest diversity is in western Palaearctic and North African regions and many species of occur in Europe. Notable among the genera occurring in the western Palaearctic and North Africa are Lydmorphus Fairmaire, 1882 with >40 species, Lydus Dejean, 1821 with 15 species, Muzimes Aksentjev, 1988 with about 15 species, Oenas Latreille, 1802 with 14 species and Alosimus Mulsant, 1857 with about 30 species.

    • Meloini Gyllenhal, 1810 includes 7 genera, 6 of which are small and localized; Spastomeloe Selander, 1985 (3 spp.) from Peru, Spastonyx Selander, 1954 (2 spp.) is Nearctic, and the monotypic Epispasta Selander, 1960 and Lyttomeloe Denier, 1960 from South America. The tribe is best known for the genus Meloe Linnaeus, 1758 which is a mostly Holarctic group of >150 species in at least 16 subgenera, diversity is greatest in Asia; 22 are recorded from the Nearctic region and of the 20 or so central European species 8 have been recorded from the UK.

    • Mylabrini Laporte, 1840 includes 11 genera distributed throughout warmer regions of Africa and the Palaearctic, it is a large and diverse group dominated by several very large genera with by far the greatest diversity in Africa. Several genera are widespread and extend into southern Europe e.g. Mylabris Fabricius, 1775 (>200 spp.), Hycleus Latreille, 1817 (about 130 spp.) and Actenodia Laporte, 1840 (>40 spp,) although are most diverse in Africa while others e.g. Ceroctis Marsuel, 1870 (>140 spp.) and Croscherichia Pardo Alcaide, 1950 (about 20 spp.) are restricted to Africa.

    • Pyrotini MacSwain, 1956 includes about 100 species in 10 genera and is almost entirely restricted to the Noetropical region, with the exception of Pseudomeloe Fairmaire & Germain, 1863, which includes about 50 species, all are very small and of restricted distribution, about 30 species of the single genus Pyrota Dejean, 1834 ( >40 spp.) occur in the United States.

Mylabris cincta A. G. Olivier, 1811

Description

Adult meloids are very diverse in general appearance and the UK species, while fairly representative of large numbers of species throughout the world, hardly do justice to this diversity. Adults are of 2 general forms; elongate with the elytra covering the abdomen, or variously broadly oval or elongate with relatively short elytra leaving much of the abdomen exposed. Most are between 7 and 30mm and have large, quite cylindrical and rather soft-bodies and long legs. They are generally glabrous, lacking any dense pubescence or scales but many have stiff erect setae, especially across the forebody, and there are many exceptions e.g. species of Epicauta may have finely and quite densely pubescent elytra while some Nemognatha may be finely pubescent throughout. Colour varies greatly, the overall dull black or blue colouration of our Meloe species is common, and an unusual variation on this is seen in the western European and North African species Berberomeloe majalis (Linnaeus, 1758) as well as in the Nearctic genus Megetra LeConte, 1859, but more generally many have bright aposematic colouration and many are strikingly patterned, especially in tropical regions, the brilliant metallic green of Lytta is well-known but to fully appreciate the family various tropical genera need to seen, more especially Mylabris, Pyrota, Cissites. In terms of overall colour some species e.g. some Hycleus, rather in the manner of various longhorns, also superficially resemble wasps. A general feature is the large abdomen compared with the forebody, and this is often emphasized by small elytra that overlap at the base and diverge widely towards the apex, this disparity in body proportions is well-demonstrated in Cysteodemus wislizeni LeConte, 1851 from New Mexico, here the abdomen is disproportionally huge and mostly covered by extremely convex elytra that arch forward over the pronotum when viewed from above, its common name of ‘Black Bladder-bodied Meloid’, is only partly appropriate as while the habitus is rather grotesque it is a very attractiv

bright metallic blue. The head is always fully exposed and varies from steeply declined anteriorly to almost flat, in the plane of the body, it is as wide as or wider than the pronotum and has a very narrow neck, it varies from very convex to almost flat and the temples are variable but often long and rounded at the base, sometimes very long or dilated, the eyes vary from almost flat to convex and strongly protruding, and from widely transverse; in some extending to the ventral side of the head, to round or emarginate. Antennae 11-segmented and short; usually moniliform or filiform and sometimes dimorphic with various intermediate segments modified in the male.  In various exotic species they may be modified with distal segments widely transverse or forming a specialized compound or 1-segmented club. Mandibles with a well-developed mola and simple, bi- or tridentate apically, labial palps small and very variable, maxillary palps 4 or 5 segmented, usually short but occasionally e.g. in Onyctenus Le Peletier & Audinet de Serville, 1828 (from Australia) very elongate, the terminal segment usually cylindrical or fusiform. Prothorax quadrate to transverse, cylindrical to flattened above and without lateral borders, usually narrower than the head and pronotum, rounded or distinctly angled laterally with distinct posterior angles but often rounded anteriorly, in many cases campanulate. In most cases the surface is evenly convex and lacking structure, the punctation is often strong and dense and in many there is a central longitudinal impression, at least towards the base where it may diverge or end in a median depression or fovea. Prosternal process absent or small, only extending between the coxae but not reaching the mesosternum, coxal cavities circular to elongate, open behind and usually contiguous. Mesocoxae oblique, closely approximated and often recessed into mesocoxal cavities. Metasternum often strongly convex, coxae contiguous or nearly so and widely transverse, often extending to meet the elytra. Elytra broadly of 2 types; long, near-parallel sided and entirely covering the abdomen, or short, overlapping at the base, individually tapered apically and variously reflexed laterally. Short elytra lack striae and vary from smooth and finely punctured to very strongly punctured or sculptured, often in a mosaic pattern. Long elytra lack regularly punctured striae although in some exotic species there may be up to 6 rows of punctures or longitudinal impressions, and are usually randomly punctured, this varies from very fine to very strong and confluent, in some there are a few rather ill-defined longitudinal costae and in some exotic species numerous small and sharply-defined longitudinal carinae. Hind wings very variable, in most short elytra species they are absent, otherwise absent, reduced or fully developed.  Pro- and mesocoxae are convex and tend to be prominent, metacoxae weakly convex or flat, trocanters large and exposed, especially the meso- and metatrocanters, trocanter-femoral junction long and oblique. Femora and tibiae are usually unadorned, weakly curved and moderately long and slender, in most they are to some extent curved and in some this is dimorphic. Tarsi always 5-5-4, without any contrasting bilobed segments, segments generally lack ventral lobes, claws very variable; simple, bifid or serrate, often with a basal or median lobe, in extreme cases they entire claw id deeply divided so that there appear to be 4 separate claws. Abdomen may be narrow and concealed beneath the elytra or widely expanded and mostly exposed, in females often very long and almost entirely exposed, the sternites articulated and moveable, in life very much so.

Ecology

Adult meloids are phytophagous, in the UK feeding mostly on flower parts, pollen and nectar but many exotic species consume foliage of a range of plant families, especially Asteraceae, Leguminosae, Apiaceae, solonaceae, Fabaceae, Malvaceae, Convolvulaceae and Solonaceae. Many are pests of various crops and ornamental flowers etc. including potato, tomato, legumes, flax, tobacco and mango etc. and because many are gregarious and affect flower development, the damage may be significant among commercial crops. In certain tropical areas, and especially across Africa, where farming tends to be small-scale and only partially mechanised, they are among the most serious pests of many crops and notorious among them are various species of Hycleus and Mylabris which tend to be sporadically extremely common.  So far as is known meloids are hypermetamorphic parasites, undergoing several distinct and uniquely adapted forms as larvae which allow them to find and develop among their hosts. Hosts include other insects, mostly Orthoptera and Hymenoptera, and meloid larvae usually consume the eggs or larvae and often the host provisions within nests etc. Two general strategies are known; some develop within orthopteran egg cases while others use various bees. Meloids are generally very fecund, producing thousands of eggs which are laid in masses on the adult foodplants (as in many Nemognathinae) or in soil or under stones close to host nesting sites (as in Meloinae), and over the season a female will repeatedly mate and produce large batches of eggs. First instars, or triungulins, are louse-like, lightly sclerotized and very mobile, they may search and find prey on their own or become attached to a bee in order to be carried to the nest site; in temperate early spring masses of triungulins emerge from the ground together and climb nearby flowers where they wait for visiting bees, flowers may become covered in hundreds of larvae and at this time mortality may be very high as many are carried off on inappropriate insects. To facilitate attachment to a visiting bee they have specialized triple curved claws, hence the name-tri, or three, and ungulus, or claw. Once transferred to the nest the triungulin larvae enter cells and begin to feed, many are specialized and develop in solitary bee nests while others develop either in a single cell within a comb or consume the contents of a cell and then burrow into adjacent cells. After an initial phase of rapid feeding the triungulin will become inactive for a while and then moult to produce a very different, rather scarabaeiform, larva that will feed and grow rapidly and undergo several more moults before it is fully-grown. The fully developed larva will then produce a chamber within the nest and during the sixth or seventh instar stage will become heavily sclerotized, immobile and lack mouth parts, rather in the style of a pupa. During this ‘coarctate’ phase it undergoes major body reorganization and respiration may drastically reduce in response to environmental conditions, so allowing long term survival, sometimes over more than a year. Development continues as a further and final scarabaeiform instar emerges, this may immediately construct a chamber and pupate or may feed for a while before doing so. Many temperate species overwinter as a coarctate larva and continue to develop and pupate in the spring, while some overwinter in the adult stage or as diapausing egg or triungulin larvae, and most species are univoltine. Variations on the life-cycle are seen in exotic species where larvae may pupate directly from the coarctate phase or may return to the coarctate state after a period of growth as a final instar, such strategies are presumably a response to varying conditions or allow a multivoltine cycle; in warmer climates many have a very long or even year-round appearance as adults. Our UK fauna includes 10 species of 3 genera although another species, Stenoria analis Schaum, 1859 occurs in the Channel Islands and is thought likely to occur here in the future. It is a widespread but sporadic and generally scarce species of southern Europe and North Africa, the common name of ivy bee blister beetle is in reference to its host, the ivy bee (Colletes hedarae Schmidt & Wastrich, 1993), although other hosts have been recorded. Lytta vesicatoria is very local and rare and recorded recently only from the Isle of Wight. Sitaris muralis, a parasite of solitary bees of the genus Anthophora Latreille, 1803, was for a long time known from only a single locality in the New Forest but is now recorded from several sites in Hampshire and Dorset and appears to be spreading. Of our 8 species of Meloe 3 are considered long extinct while 2 more have only recently been re-discovered, having not been recorded in recent decades and suspected to have become extinct as well. The two most widespread species are M. proscarabaeus Linnaeus, 1758 (the Black oil Beetle) and M. violaceus Marsham, 1802 (the Violet oil Beetle) although both are very local and neither is common, while M. rugosus Marsham, 1802 (the Rugged oil Beetle) is a very local insect in the southwest. All our Meloe species are typical bee parasites; they occur from early spring to mid-summer and are most often encountered on open soil as they mate or search for suitable sites for their oviposition burrows.

The common name of ‘oil beetles’ refers to the habit of many, including our own species of Meloe, of releasing drops of oily haemolymph from between various body segments when alarmed or disturbed, and this contains, in varying amounts according to the species, a toxic and highly irritating chemical called cantharidin which may cause severe swelling or blistering to sensitive skin, hence the other common name of ‘blister beetles’. Perhaps the most notorious, if not the most severe, example of the toxicity of meloids is provided by Lytta vesicatoria (Linnaeus, 1758) (Meloinae, Lyttini) or Spanish fly, which was formerly used by apothecaries as a source of the blistering agent; adult beetles were killed, dried and ground up and the powder used for a variety of things e.g. removing warts or tattoos, but mostly as an aphrodisiac, for those wishing to obtain a spouse, or as a poison for those wishing to dispose of one, obviously a very popular concoction, but while the toxic effects cannot be argued against, and there have been several famous cases of successful application, its claimed aphrodisiac qualities are nonsense. Cattle and horses may be severely affected by ingesting hay or silage products containing dead beetles, this may cause ‘cantharidin toxicosis’ which produces depression, toxic shock or even death. Only males synthesize the poison as it acts as a female attractant but they pass it to females during courtship or mating.

UK Species

Meloe autumnalis

Meloe rugosus

Meloe brevicollis

Meloe variegatus

Meloe cicatricosus

Meloe mediterraneus

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