Hoplia mexicana^{Harold, 1869}

Third instar (Figs. 1–11 and 13). Description. Head (Fig. 2). Maximum width of head capsule: 1.8–2.0 mm. Surface of cranium smooth, with scattered minute punctures, pale yellowish. Frontal and epicranial sutures hidden. Frons with 2 exterior frontal setae, 3–4 posterior frontal setae, 1 anterior frontal seta, 1 anterior angle seta, 3 dorsoepicranial setae, 8–9 epicranial setae on each side and 7–9 setae behind each antennal support. Clypeus with 2 central setae and 4 lateral seta on each side. Labrum nearly symmetrical with rounded lateral margins irregularly bordered, anterior margin projected forward with irregular border, 6–7 posterior setae, 1 central seta and 3–4 lateral setae on each side. Stemmata absent. Epipharynx (Fig. 5) 1.0–1.1 mm wide, 0.8–0.9 mm long, epizygum absent and zygum as a irregular, ovate, reddish yellow plate. Haptomerum weakly raised, with 4 heli; each plegmatia formed by 8–10 short plegmata; proplegmatia absent. Each acanthoparia with 10–12 spinose setae. Dexiophoba and laeophoba absent. Dexiotorma narrowed, slightly sinuose. Laeotorma elongate and narrowed, with sclerotized plate unciform, raised. Sense cone short. Crepis weakly defined. Left chaetoparia with 28–30 spinose and medium size setae mixed. Right chaetoparia with 30–36 short, stout setae. Mandibles (Figs. 3 and 4) without ventral stridulatory area; scissorial area in both mandibles without distal blade. Right mandible with 1 small preapical tooth, inner margin simply curved, and distal lobe (M1) of molar area scarcely developed. Calx short. Left mandible with 1 small preapical tooth, inner margin simply curved, brustia moderately setose. Acia absent. Maxillae (Figs. 6–9). Mala with 1 uncus on apex of galea, 3 unci surrounded by 3–4 stout heli on apex of lacinia; stridulatory area with 8 small teeth with anteriorly directed points. Hypopharyngeal sclerome (Fig. 10) asymmetrical with raised and curved projection on the right side. Fourth antennomere elongate, with distal half narrowed, with 1 ovate, dorsal sensory spot on basal half and 2 ventral sensory spots.

Figs. 1–5 Third instar larva of Hoplia mexicana. 1, lateral habitus. 2, head, frontal view. Mandibles, ventral view: 3, left. 4, right. 5, epipharynx. 

Figs. 6–12 Hoplia mexicana. 6–11: third instar larva. Maxillae: dorsal view: 6, left. 7, right. Mesial view: 8, left. 9, right. 10, labium and hypopharynx. 11, raster. 12, MALE pupa, lateral view. 

Figs. 13–16 Hoplia mexicana. 13, Third instar, lateral view. 14–16: male pupa. 14, ventral view. 15, lateral view. 16, dorsal view. 

Thorax. Respiratory plates light yellow, scarcely curved, “C” shaped (Figs. 1 and 13) 0.12–0.14 mm long, 0.10–0.11 mm wide, bulla small, slightly raised, rounded, distance between lobes longer than dorso-ventral diameter of bulla; microscopic holes of respiratory plate elongate-oval in outline and arranged in irregular transverse rows. Lateral sclerome of pronotum not defined. Pro-prescutum with 20–22 long setae regularly distributed; proscutum with 8–9 slender long setae; mesoprescutum with transverse row of 10–12 long setae; mesoscutum with 12–16 setae; mesoscutellum with row of 8–10 slender long setae; metaprescutum with transverse row of 12–16 mixed short and long setae; metascutum with 10–12 setae; metascutellum with transverse row of 10–12 mixed short and long setae (Figs. 1 and 13). Protarsal claws long, narrowed, sharply pointed, with 1 prebasal inner seta and 1 lateral external seta, moderately longer than mesotarsal claws; meso-tarsal claws long, sharply pointed, with pre-basal and lateral setae; metatarsal claw short, rounded, with 2 setae, much shorter than mesotarsal claws. Apical metatarsomere shortened, rounded, with ventral side clearly convex.

Abdomen. Respiratory plates light yellow, slightly curved, “C” shaped; on segments I–IV with similar diameter, 0.12–0.13 mm long, 0.10 mm wide; plates on segments V–VII are slightly smaller, 0.10–0.11 mm length, 0.09 mm width. Plate on segment VIII is smaller than preceding. Dorsa of abdominal segments I–VI each with dense vestiture of yellow stout, short setae; dorsa of segments VII–IX with transverse rows of 20–28 slender, short setae. Venter of abdominal segments I–VIII with transverse rows of 14–18 slender, long setae; venter of segment IX with transverse rows of 12–16 mixed short and long setae.

Raster (Fig. 11) with each palidia formed by 9–11 pali, convergent toward basal and distal extremes, septula wide, oval; tegilla with 20–26 short, stout setae; campus with 14–18 slender, short setae; barbula much more densely setose. Dorsal anal lip with dense vestiture of short setae. Ventral anal lip with scattered short setae toward sides and distal border narrowly notched at middle. Anal slit “Y” shaped. Approximate dorsal body length 16–17 mm.

Description: body length 7.5–7.8 mm. Widest width 4.4–4.5 mm. Head. Surface glabrous, strongly deflexed; frons convex with two rounded prominences; clypeus widely concave on the center; labrum, mandibles, maxillae and palps discernible; antennal theca briefly expanded, stout with apex rounded; eyes small (Fig. 14). Thorax: surface glabrous. Pronotum convex, surface slightly irregular, anterior angles prominent, posterior angles rounded. Meso- and metanotum well-differentiated. Elytral and posterior wing thecae closely appressed, curved ventrally around the body; elytral thecae with irregular depressions and large, prominent, humeral tubercles (Figs. 12 and 15); thecae of the wings slightly longer than elytral thecae. Protibiae with apical and preapical tubercles clearly developed. Meso and metatibiae with apical tubercle. Abdomen: segments I–VI clearly wider and shorter than the distal segments VII–VIII, without dioneiform organs, but segments II–IV with pairs of prominent tubercles and segment V with increased posterior border (Figs. 12 and 15–16). Pleural lobes rounded. Spiracle I elongate, with fine peritreme and covered by wing thecae; spiracles II–IV ovate and high, prominent, with narrow sclerotized peritreme; spiracles V–VIII closed. Sutures between segments VIII and X not complete, partially fused. Last segment slightly pruinose, without urogomphi.

Last abdominal segment of male with large dorsal and lateral rounded prominences, and genital ampulla ventrally exposed (Figs. 12 and 14–16); female without such prominences at the apex of abdomen.

Specimens examined. Four third instar larvae, four pupae and two exuviae of third instar larvae reared to adults, collected at Mexico: Oaxaca: Santa María Tlahuitoltepec municipality, Cerro Zempoaltepetl, 2400 m, 8-VI-2010, A. Ramírez col. (IEXA).

Comments. The third instar larvae of H. mexicana resemble those of H. callipyge and H. equina, but H. mexicana has 4 heli on haptomerum, and palidia with well-defined septula. Hoplia callipyge and H. equina each have1 helus on the haptomerum and only subtriangular teges of long hamate setae with curved tips. The dense setiferous vestiture on the dorsum of abdominal segments I–VI and the sides of the last segment, aid in distinguishing H. mexicana from the known larvae of other Mexican melolonthine scarabs. Projections on the humeral area of the elytra and the middle of the abdominal segments of the pupae of both sexes may act as auxiliary supports during pupal development. These projections possibly aid in regulating humidity near the body wall. This type of structure is also observed in pupae of some Scarabaeinae (^{Edmonds and Halffter, 1978}), and Ceratocanthinae (^{Morón and Arce, 2003}).

Biology. Hoplia mexicana is known only from the northern mountains of the Mexican state of Oaxaca, at localities with elevations between 2300 and 2500 m. Larvae have been collected in rich organic soil of oak and coniferous forest. Adults are rarely attracted to electric lights during summer, and their host plants are unknown.

Hoplia squamifera ^{Burmeister, 1844}

Third instar (Figs. 17–24). Description. Head (Fig. 18). Maximum width of head capsule: 2.1–2.4 mm. Surface of cranium smooth, with scattered minute punctures, pale yellowish. Frontal and epicranial sutures hidden. Frons with 2 exterior frontal setae, 1 posterior frontal seta, anterior frontal seta absent, 1 anterior angle seta, 3–4 dorsoepicranial, 14–18 epicranial setae on each side and 6–8 setae behind each antennal support. Clypeus with 2 central setae and 4 lateral setae on each side. Labrum nearly symmetrical with rounded lateral margins irregularly bordered, anterior margin projected forward with irregular border, basal transverse keel with 5 posterior setae, 1 anterior-central seta and 5–6 lateral setae on each side. Stemmata absent. Epipharynx (Fig. 21) 1.6–1.9 mm wide, 1.0–0.2 mm long. Epizygum absent and zygum as irregular, ovate, reddish yellow plate. Haptomerum weakly raised, with 4 heli; each plegmatia formed by 9–10 short plegmata; proplegmatia absent. Each acanthoparia with 9–10 spinose setae. Dexiophoba and laeophoba absent. Dexiotorma narrowed, slightly curved. Laeotorma elongate and narrowed with sclerotized plate unciform, raised. Sense cone short. Crepis weakly defined. Left chaetoparia with 30–34 spinose and medium size setae mixed. Right chaetoparia with 28–30 short, stout setae. Mandibles (Figs. 19 and 20) without ventral stridulatory area; scissorial area in both mandibles without distal blade. Right mandible with 1 small rounded, preapical tooth, inner margin simply curved, and distal lobe (M1) of molar area scarcely developed. Calx short. Left mandible without preapical tooth, inner margin simply curved, brustia moderately setose. Acia absent. Maxillae (Fig. 23). Mala with 1 uncus on apex of galea, 3 unci surrounded by 3–4 stout heli on apex of lacinia; stridulatory area with 10–11 small teeth with anteriorly directed points. Hypopharyngeal sclerome (Fig. 22) asymmetrical with curved projection on the right side. Fourth antennomere elongate, with distal half narrowed, with 1 ovate, dorsal sensory spot on basal half and 2 ventral sensory spots.

Figs. 17–21 Third instar larva of Hoplia squamifera. 17, lateral habitus. 18, head, frontal view. Mandibles, ventral view: 19, left. 20, right. 21, epipharynx. 

Figs. 22–25 Hoplia squamifera. 22–24: third instar. 22, labium and hypopharynx. 23, left maxilla, dorsal view. 24, raster. 25, female pupa, lateral view. 

Thorax. Respiratory plates light yellow, scarcely curved, “C” shaped (Fig. 17) 0.11–0.15 mm long, 0.10–0.12 mm wide, bulla small, slightly raised, rounded, distance between lobes longer than dorso-ventral diameter of bulla; microscopic holes of respiratory plate elongate-oval in outline and arranged in irregular transverse rows. Lateral sclerome of pronotum not defined. Proprescutum with 14–18 long setae regularly distributed; proscutum with 5–6 slender long setae; mesoprescutum with transverse row of 8–9 long setae; mesoscutum with 10–12 setae; mesoscutellum with row of 6–8 slender long setae; metaprescutum with transverse row of 9–12 mixed short and long setae; metascutum with 8–10 setae; metascutellum with transverse row of 6–8 mixed short and long setae (Fig. 17). Protarsal claws long, narrowed, sharply pointed, with 1 pre-basal inner seta and 1 lateral external seta, moderately longer than mesotarsal claws; mesotarsal claws long, sharply pointed, with pre-basal and lateral setae; metatarsal claw short, rounded, with 2 setae, much shorter than mesotarsal claws. Apical metatarsomere shortened, rounded, with ventral side clearly convex.

Abdomen. Respiratory plates light yellow, slightly curved, “C” shaped; on segments I–IV with similar diameter, 0.13–0.14 mm long, 0.11 mm wide; plates on segments V–VII slightly smaller, 0.11–0.12 mm long, 0.10 mm wide. Respiratory plate on segment VIII smaller than plate on preceding segment. Dorsa of abdominal segments I–VI each with dense vestiture of yellow stout, short setae; dorsa of segments VII–IX with transverse rows of 18–20 slender, short setae. Venter of abdominal segments I–VIII with transverse rows of 10–12 slender, long setae; venter of segment IX with transverse rows of 10–12 mixed short and long setae. Raster (Fig. 24) with each palidia formed by 10–12 pali, convergent toward basal and distal extremes, septula wide, oval; tegilla with 24–30 short, stout setae; campus with 14–16 slender, short setae; barbula densely setose. Dorsal anal lip with dense vestiture of short setae.

Ventral anal lip with scattered short setae at sides and distal border narrowly notched at middle. Anal slit “Y” shaped. Approximate dorsal body length 16–18 mm.

Pupa (Figs. 25 and 26). Description: body length 7.8–8.1 mm. Widest width 4.5–4.6 mm. Head. Surface glabrous, strongly deflexed; frons convex with two rounded prominences; clypeus widely concave on the center; labrum, mandibles, maxillae and palps discernible; antennal theca briefly expanded, stout with apex rounded; eyes small (Fig. 25). Thorax: surface glabrous. Pronotum convex, surface slightly irregular, anterior angles briefly prominent, posterior angles widely rounded. Meso- and metanotum well-differentiated. Elytral and posterior wing thecae closely appressed, curved ventrally around body; elytral thecae with irregular longitudinal striae and large, prominent, semiconical humeral tubercles (Figs. 25 and 26); thecae of the wings slightly longer than elytral thecae. Protibiae with apical and preapical tubercles clearly developed. Meso and metatibiae with apical tubercle. Abdomen: segments I–VI clearly wider and shorter than the distal segments VII–VIII, without dioneiform organs, but segments II–IV with pairs of prominent tubercles and segment V with thicker posterior border (Figs. 25 and 26). Pleural lobes rounded. Spiracle I elongate, with fine peritreme partially covered by wing thecae; spiracles II–IV ovate and high, prominent, with narrow sclerotized peritreme; spiracles V–VIII closed. Sutures between segments VIII and X incomplete, partially fused. Last segment slightly pruinose, without urogomphi. Last abdominal segment of male with dorsal and lateral rounded prominences, and genital ampulla ventrally exposed (Fig. 26); female without such abdominal prominences (Fig. 25).

Fig. 26 Male pupa of Hoplia squamifera, with third instar exuviae on its abdominal apex. 

Specimens examined. Seven third instar larvae, collected at Mexico: Chiapas, Amatenango del Valle municipality, El Madronal, 2400 m, 20-I-1997, corn field, C. Ramírez col. (IEXA). Two pupae and 2 exuviae of third instar larvae reared to adults, with same data, except 24-X-2005 (IEXA). Two third instar larvae: Chiapas, Amatenango del Valle, 28-X-1996, corn field, C. Ramírez; 4 third instar larvae with same data, except 4-XI-1996; 5 third instar larvae 24-IX-2001 (IEXA, ECOSUR).

Comments. The larvae of Hoplia squamifera resemble those of H. mexicana, but lack antero-frontal setae, have 9–10 wide plegmata on each plegmatia, and have wide septula, whereas Hoplia mexicana have 2 antero-frontal setae, 7–8 narrow plegmata on each plegmatia and narrower septula.

Pupae of both Hoplia mexicana, and H. squamifera lack urogomphi and dioneiform organs. This fact is very interesting because, as far as we know, no other scarab group possesses such a combination of characters. For instance, with the exception of Manopus biguttatus Laporte, 1840 (^{Neita-Moreno et al., 2012}), known pupae of Melolonthinae have urogomphi and lack dioneiform organs (Table 1). On the other hand, known pupae of Rutelinae and Dynastinae, lack urogomphi but, in contrast, have dioneiform organs (^{Morón, 1993}). With the combination of these characters, and the unique paired supporting organs in the humeri and tergites, the pupae of Hopliinae are very distinct from other subfamilies of Melolonthidae. Description of the pupae of many other genera of Melolonthidae surely will offer more characters to be tested in future phylogenetic analyses of Scarabaeoidea.

Biology. Hoplia squamifera has been recorded from the Mexican mountains of northern Chiapas and Oaxaca states, southern Veracruz state, and in western Guatemala at localities with elevations between 1200 and 2100 m. Larvae have been collected in soil of corn fields in northern Chiapas, Mexico. Adults are frequently attracted to electric lights during spring and summer, but their host plants are unknown.