CRIOCERINAE Latreille, 1804
These colourful beetles will usually be found wherever their respective host plants occur. Most are common and widespread throughout England and Wales.
In Chrysomelid terms this is a small subfamily; about 1500 species are included in (at least) 25 genera and 3 tribes. The group is cosmopolitan with by far the greatest diversity in tropical and sub-tropical regions. The Pseudocriocerini Heinze, 1962 includes 3 species of Pseudocriocerus Pic, 1916 from Indonesia, Madagascar and Java. The Criocerini Latreille, 1807 comprises about 7 genera (although some are being split) including our familiar Lilioceris Reitter, 1912 and Crioceris Geoffroy, 1762. Several of the genera are small and have very restricted Old World distributions; 5 genera, including the quaintly-named Elisabethana (Heinze, 1928) with about 15 species, are restricted to Africa. The two largest genera include more than half the species; Lilioceris with about 150, and Crioceris with about 65, are widespread Old World groups although a few adventives and introductions have become established in the Nearctic region and are now significant economic pests; C. asparagi Linnaeus, 1758, the asparagus beetle, C. duodecimpunctata Linnaeus, 1758, the 12-spotted asparagus beetle, Liliocerus lilii (Scopoli, 1763) the lily beetle and L. cheni Gressit & Kimoto, 1961, the air-potato beetle. The Lemiini Heinze, 1962 includes about a dozen genera, although again these are being split, and is the largest tribe. Oulema Des Gozis, 1886 includes more than 130 species and is native to both the Old and New Worlds. Lema Fabricius, 1798 includes more than half of the subfamily although some sub-genera are being raised to generic rank e.g. Neolema Monrós, 1951 includes about 10 New World species. Overall about one-third of the subfamily occurs in the New World with about 150 species from Central America. The Oriental and Palaearctic regions each include about 10% of the total while the African and Neotropical regions account for about 20% each. Needless to mention most regions include many endemics. The Australian fauna is relatively poor with 4 genera and about 20 native species, and none are known from Tasmania.
The typical habitat for most species is open grassland, scrub, pasture and forest and wetland marginal situations where all stages are closely associated with the host plants. Several species, especially in the large genus Oulema, are important agricultural pests and some have been used as bio-control agents and so are now distributed beyond their natural range; the European Lema puncticollis (Curtis, 1830) has been used in Canada to help control thistles and various Neotropical Neolema are used to control invasive Tradescantia weeds. Oulema melanopus (Linnaeus, 1758), the cereal leaf beetle, and O. oryzae (Kuwayama, 1929), the rice beetle, are serious pests of grain crops throughout the world. Host plant associations of about 20% of species are known and while at least 15 families of plants are known to be hosts the majority of species are monocotyledons: Commelinaceae, Marantaceae, Asparagaceae, Dioscoraceae, Zingerberbiaceae, Orchidaceae, Poaceae and Liliaceae. Some species have been reported from Cycads (Lilioceris) and, doubtfully, from ferns. Adults and larvae of most species feed externally upon leaves and stems while a few have been recorded from various flower parts and some larvae e.g. Neolema terminalis (Lacordaire) develop in flower buds. Some Neolema, Lema and Oulema are stem-borers and two species, O. pumila Venci & Aiello, 2012 from Panama, and the Argentinian Neolema quadrivittata Boheman, 1858 are leaf-miners. Oulema reclusa Venci & Nishida, 2008 from Thailand is known to form galls. Feeding patterns and damage are characteristic and sometimes diagnostic for a species. The majority of species are monophagous or oligophagous and some genera (etc.) are restricted to certain plant families e.g. Old World Crioceris, Elisabethana and Sigrisma (an African genus variously included in Crioceris) develop on Asparagaceae while many Oulema feed on Poaceae. Adult colouration is aposematic and many are mimics of other leaf-beetles e.g. various Galerucinae. When alarmed many adults stridulate and secrete defensive fluids from thoracic glands. Larvae possess dorsal anal openings and accumulate faecal coatings across the body, these contain recycled host chemicals which are known to deter potential predators such as ants, and they also tend to feed in close groups as a defensive behaviour.
The larvae are often conspicuous on the host plant, especially Crioceris (etc.) among the narrow foliage of asparagus. They are short and broad, pale to dark grey or mottled above and pale below with a darker, transverse head, short legs, conspicuous spiracles and unmodified terminal abdominal segment.
Adults are glabrous and shiny, most species are brightly coloured and many are patterned and/or metallic; it really is worth seeing some of these e.g. the South African Lema trilineata Olivier, 1808, ‘the tobacco slug’, is yellow with longitudinal dark stripes to the suture and lateral margins, and the southeast Asian Lilioceris adonis (Baly, 1859) and L. major (Pic, 1916) are striking. Most are medium sized, 4-8mm although some Oulema are tiny, around 1.5mm, and some Lilioceris up to 14mm. Females are generally larger than males. All have a characteristic form; from above the head is transverse, and the pronotum is narrower than the parallel-sided elytra. Head prognathous and about as wide as the pronotum, with temples constricted behind convex and prominent eyes so forming a distinct neck. Vertex generally convex, variously punctured and microsculptured, separated from the eyes by an oblique depression and often with a median longitudinal impression. Eyes entire to weakly, in Oulema, or strongly, in Lema, emarginate. Antennal insertions widely separated, much more so than the length of the basal segment, and visible from above. Antennae 11-segmented and filiform or widened towards the apex, and generally with the basal segments shorter than the others. Frontoclypeal suture absent, clypeus and labrum distinct; the labrum transverse and truncate. Mandibles short and curved, bidentate to multi-dentate and variously toothed internally. Apical segment of the maxillary and labial palpi cylindrical and narrowed towards the apex. Pronotum quadrate to slightly transverse and constricted across the middle or towards the base, giving a pinched appearance from above, parallel-sided to widest at the base, anterior angles distinct to simply rounded, posterior angles distinct and often acute. Posterior margin often strongly bordered, lateral and anterior margins simple. The surface is usually sparsely and finely punctured although sometimes with shallow depressions e.g. in some Pseudocriocerus. Prosternum short in front of round coxal cavities, the process narrow and acute; not expanded posterior to the coxae. Mesocoxal cavities round and narrowly separated, metacoxal cavities transverse but not extended to reach the elytral epipleura, narrowly to widely separated. Scutellum visible; triangular to rounded and sometimes raised. Elytra elongate and flattened, completely covering the abdomen and continuously rounded apically, parallel-sided to rather strongly constricted at, or in front of, the middle, with prominent shoulders and very narrow explanate margins. Each with 9 or 10 rows of punctures and in some with a scutellary row, in a very few e.g. the Central American Metapoceris alternans (Lacordaire, 1845) with variously developed longitudinal carinae. Hind wings well-developed and most species are good fliers. Abdomen with five visible ventrites, the first more than twice the length of the second and lacking post-coxal lines. In males segments 2-4 have tufts of setae. Legs well-developed and proportionally long, the base of the femora sometimes touch the coxae due to the strongly oblique trocanter/femora joint. Femora generally weakly thickened although in the Neotropical genus Neolema they may be broadly dilated. In some species there are large spines or rows of small teeth on the posterior margin. Tibiae generally slender and smooth along the external margin although the metatibiae have small basal or medial spurs. Tarsi 5-segmented with the third bilobed and the fourth reduced, so appearing tetramerous. The basal segment is longer than the second, and 1-3 have a dense ventral clothing of adhesive setae. Claws free in Criocerini, or connate in Lemiini, empodium very reduced, often not visible.