Clypeus expanded, covering mouthparts. Mandibles lamelliform.
Description: Adults 3-58 mm in length. Dorsal surface often conspicuously setose or scaled; color usually reddish brown or black (i.e., Diplotaxis, Phyllophaga, Serica), sometimes with metallic blue or green lustre (Dichelonyx) or distinctly marked with patches of scales (Hoplia, Polyphylla). Head usually unarmed (except in Chaunocolus), with mandibles usually well developed, sclerotized, completely concealed from above, or nearly so. Antennal insertions not visible from above; antennae 7 to 10-segmented, antennal lamellae folding tightly into a 3 to 7-segmented club, club oval to elongate, glabrous or with only a few setae. Labrum located below clypeus or on apical clypeal margin (Oncerini, Sericini), transverse, narrowed, or conical. Thorax with pronotum unarmed; scutellum exposed. Elytral margins straight, without notch posterior to humerus. Mesepimeron usually covered by base of elytra (slightly exposed in Gymnopyge). Legs with claws simple; claws cleft, toothed, serrate or pectinate; metatarsal claws usually paired, equal in thickness and length or single (Hoplia); apex of metatibia with 1 or 2 spurs; spurs mesad, adjacent or separated by basal metatarsal segment. Abdomen with 7 or fewer pairs of abdominal spiracles, with posterior abdominal spiracles usually located in sternites, tergites or pleural membrane (see Acoma and Podolasia), with 1 pair exposed beneath edge of elytra; 5 or 6 visible sternites fused, sutures usually visible at least laterally, or completely effaced (Chasmatopterini), the sixth sternite (when present) sometimes partially or completely retracted within fifth (Diplotaxini); trace of suture between fifth sternite and propygidium usually evident or entirely absent (Diplotaxini); pygidium exposed. Sexual dimorphism not strongly developed; males usually with abdomen less convex, with longer tarsi and antennal club than females, some genera with males having specialized front claws (Hypotrichia) or with protibial and metatibial spurs absent (some male Macrodactylini).

Classification Status
Recognition of taxa as tribes or subfamilies has not been applied consistently (see discussion under Chasmatopterini and Oncerini). Moreover, the tribal classification is in a relative state of confusion due to the lack of definition and inconsistent use of characters (Hardy 1978b; Ratcliffe 1991). This state of affairs is further exacerbated by the fact that descriptions of the majority of genera and species published before 1940 are largely inadequate and seldom accompanied by illustrations, making reliable determinations difficult without examination of type specimens. Early workers rarely consulted types, resulting in numerous synonymies and incorrect placements. The present work is not designed to resolve these issues but is intended to make North American melolonthine genera recognizeable. Not until the completion of a comparative analysis of all genera, including the larvae, will the higher classification of the Melolonthinae achieve some stability and begin to reflect the phylogenetic relationships of the group.

The North American melolonthines have not been considered in their entirety for more than 140 years, although many genera have subsequently been revised. Early attempts at establishing schemes of higher classification for the melolonthines were based primarily on taxa found outside of the Nearctic region. LeConte (1856) recognized the following tribes in the United States under the family Melolonthidae: Macrophyllae (Phobetus); Melolonthae (Polyphylla, Thyce); Rhizotrogi (Phyllophaga sensu latu); Diplotaxes (Diplotaxis); Sericae (Serica); Macrodactyli (Macrodactylus); Dichelonychae (Dichelonyx); Lasipodes (Podolasia, Oncerus); Hopliae (Hoplia); Glaphyri (Lichnanthe). He later modified his classification (1861) as follows: Macrophyllini, Melolonthini, Rhizotrogi, Diplotaxini, Sericini, Sericoidini (Hypotrichia), Macrodactylini, Dichelonychini, Oncerini (for Lasipodes), Hopliini, and Glaphyrini.

Gemminger and Harold (1869) recognized the following tribes with North American taxa under the family Scarabaeidae: Glaphyrini (LeConte's Glaphyrini and Lasipodes, Chnaunanthus); Melolonthini (LeConte's Hopliini, Sericini, Dichelonychini, Macrodactylini, Diplotaxini, Rhizotrogini, Melolonthinae, Macrophyllini). The catalog of Dalla Torre (1912, 1913) listed the following tribes with Nearctic representatives under the subfamily Melolonthinae: Chasmatopterini (including Lecontes Oncerini); Sericini; Liparetrini (Plectrodes, Hypotrichia); Melolonthini (Leconte's Melolonthini, Rhizotrogini, Diplotaxini); Pachydemini (LeConte's Macrophyllini); Macrodactylini (Leconte's Macrodactylini, Dichelonychini); Hopliini. These tribes were not formally characterized by Dalla Torre, leading to considerable confusion of the higher classification of the subfamily. With the subsequent addition of hundreds of genera and species since its publication, there is little basis for much of the systematic content of Dalla Torre's catalog although it remains a valuable bibliographic tool. The catalogues of Leng (1920), Leng and Mutchler (1927, 1933) and Blackwelder (1944) followed the classification of Dalla Torre. Saylor (1937b, 1938) removed the tribes Chasmatopterini and Oncerini from the Melolonthinae and considered them as separate subfamilies. On the basis of characters of known larvae, Ritcher (1966) recognized the following tribes: Sericini, Diplotaxini, Dichelonycini, Macrodactylini, Hoplini, Pachydemini, Melolonthini, and Plectrini. Hatch (1971) recognized the Diplotaxini and Dichelonycini. Arnett (1971) followed the system of Dalla Torre, with the exception of combining Saylor's Oncerinae and Chasmatopterinae within the Chasmatopterini of the Melolonthinae. Morón et al. (1997) presented the following tribal and subtribal classification for the melolonthines of Mexico: Melolonthini (Diplotaxina, Melolonthina, Rhizotrogina), Macrodactylini (Ceraspina, Macrodactylina), Hopliini (Hopliina), Sericini (Sericina), Chasmatopterini, and Pachydemini.

Useful faunal surveys, systematic catalogs, biogeographical analyses, or conservation notes on Nearctic Melolonthinae include: CANADA: Bousquet, 1991; MEXICO: Morón, 1996; Morón et al. 1997; Baja California peninsula: Saylor, 1948; Chiapas: Morón et al. 1985; Durango: Morón 1981, Morón and Deloya 1988; Hidalgo: Morón 1994; Jalisco: Morón et al. 1988; Morelos: Deloya et al. 1995; Mexico: Morón and Zaragoza, 1976; Veracruz: Morón 1979; UNITED STATES: Arnett 1971; Alaska: Bousquet 1991; Colorado: Zimmerman et al. 1991; Florida: Woodruff and Deyrup 1994; Nebraska: Ratcliffe 1991; North Dakota: Lago et al. 1979; Pacific Northwest: Hatch, 1971; western sand dune systems: Andrews et al. 1979.

The cosmopolitan Melolonthinae is one of the largest and most diverse subfamilies in the Scarabaeoidea, with approximately 750 genera and nearly 11,000 species worldwide (Houston and Weir 1992). In the New World there are approximately 90 genera.

New World Tribes
Incertae sedis

Adults and larvae of the Melolonthinae are generally phytophagous, although some adults apparently do not feed. Both adults and larvae of some genera may be of considerable economic importance (i.e., Amphimallon, Diplotaxis, Phyllophaga, Polyphylla, Maladera, Serica), damaging a wide variety of crops, pastures, and turf. Adult Phyllophaga may be so abundant locally that deciduous trees may be completely defoliated by their nocturnal feeding activities (Ritcher 1966). Adults of flower or pollen feeding species are often diurnal (Chnaunanthus, Gymnopyge, Hoplia, Macrodactylus, Oncerus), but the vast majority of melolonthines are crepuscular or nocturnal. Primarily nocturnal species in the genera Diplotaxis, Phyllophaga, Polyphylla, and Serica are usually encountered in numbers flying about lights or copulating, feeding, or resting on the foliage of host plants.

Ritcher (1966) characterized the soil dwelling, C-shaped larvae of North American melolonthines as follows: Head with mandibles lacking stridulatory area, or indistinct, with patch of minute granules; scissorial area of mandible with distal, blade-like portion which is separated from proximal tooth by scissorial notch. Galea and lacinia of maxilla fused proximally but separated distally; rarely galea and lacinia separated but tightly fitted together; lacinia with longitudinal row of 3 unci; maxillary stridulatory area without anterior process. Antennae 4-segmented; last antennal segment with single, elliptical, dorsal sensory spot. Thorax with all legs well developed, 4-segmented; each claw bearing 2 setae. Abdomen with anal opening usually angulate or Y-shaped. Lower anal lip usually with sagittal cleft or grooves. Keys to larvae: Böving 1936, 1937, 1942b, 1942c; Ritcher 1949, 1966 (see also Boving, 1942a; King, 1984).

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