Larval morphology and biology of four Netocia and Potosia species (Coleóptera: Scarabaeoidea: Cetoniidae: Cetoniinae)

The larvae of Netocia morio (Fabricius, 1781), Netocia oblonga (Gory & Percheron, 1833), Potosia opaca (Fabricius, 1787) and Potosia cuprea brancoi Baraud 1992 are described. Comparison of the morphology of both genera revealed important dif­ ferences in raster structure, mandibles and frontal setae. The systematic position of both genera based on larval characteristics is dis­ cussed. Some aspects oflarval biology are discussed.

In spite of their wide distribution, little is known about the life history and larval morphology of Cetoniinae.The most important contributions to the knowledge of Palaearctic species were provided by Golovjanko (1936), Korschefsky (1940), Van Emden (1941) and Medvedev (1952).Several years later, Klausnitzer & Krell (1997) improved the third larval instar key of Medvedev (1952) by adding the species described by other authors.How ever, none of these contributions represented a complete description and no more new descriptions of Palaearctic larvae were published.
In this study, we describe the third larval instar of Netocia morio, Netocia oblonga, Potosia opaca and Potosia cuprea brancoi.Both Netocia species and Potosia opaca occur in the occidental Mediterranean basin.Potosia cuprea (Fabricius, 1775) is widely distrib uted in Europe and it is represented by P. cuprea brancoi in the Iberian Peninsula.The larva of P. cuprea was described in part by Korschefsky (1940), Van Emden (1941) and Medvedev (1952).However, these descrip tions are of P. cuprea metallica (Herbst, 1782) (Medve dev, 1952;Klausnitzer & Krell, 1997).The aim of this study was (1) to test the validity of genus status of both genera based on larval morphology, (2) to provide a key of the third instar larvae of the species, and (3) an account of the larval biology of the species.

MATERIAL AND METHODS
A total of 6-10 adult specimens (males and females) of each species were kept in plastic breeding cages (15 cm high, 27 cm wide) with flowers (Asteraceae: Carduinae) and soil with vege table matter.The lid was an opening (12 cm in diameter) cov ered with a gauze screen.These breeding cages were maintained in an environmental chamber at 25°C : 20°C (L : D), 80 ± 5 % RH, and a photoperiod of 15L : 9D.Larvae were feed on ripe fruit (N.morio, P. opaca, P. cuprea brancoi), milled rabbit dung and decaying vegetable mater (N.oblonga).The breeding cages were examined weekly and the results recorded.Larvae col lected in the field were reared to the adult stage in the above laboratory conditions.
The different larval instars of each species were fixed in KAAD solution (Carne, 1951) for 24 h and preserved in 70% ethanol.Specimens are deposited in the Entomological Collec tion of the University of Alicante, Spain.In the description of larvae the anatomical designations of Ritcher (1966) and Mico et al. (2001) were used.
Abdomen.Abdominal spiracles similar in size.Dorsa of abdominal segments I-VIII with 3-4 rows of short setae, each posterior row with long to short setae.Abdominal segments IX-X fused, densely setose with short setae and single row of long to short setae at the middle and apex (Fig. 1).Tegilla composed of short, acute setae and sparse long straight setae.Lower anal lip with many short and curved setae and 2-3 transversal rows of long, acute setae (Fig. 5).Raster with a pair of palidia joined anteriorly; each palidium consisting of 11-15 short pali.Apex of pali round and flattened (Fig. 7).
Abdomen.Spiracles of abdominal segments I-VII similar in size, those of VIII smaller.Dorsa of abdominal segments I-VIII with 4-6 rows of short setae, each poste rior row with long to short setae.Abdominal segments IX-X fused, densely setose with short and long setae (Fig. 14).Tegilla composed of a single row of short setae on each side of palidium and many rows of longer straight, acute setae.Lower anal lip with many short and curved setae and 1 transverse row of long, acute setae at apex (Fig. 18).Raster with a pair of palidia joined anteriorly; each palidium consisting of 11-15 short pali.Apex of pali round and flattened (Fig. 20).Head.Maximum width of head capsule 4.3 mm.Cra nium (Fig. 28).Colour light yellow.Dorsoepicranium with 2 groups of short setae more or less arranged in 2 rows on each side; normally with 1 long seta on each side.Frons moderately punctate, with 1 posterior seta and 1 anterior angle seta on each side; anterior and external setae reduced to a single microseta on each side.Clypeus with 2 anterior setae and 2 external setae on each side.Postclipeus moderately punctate.Labrum (Fig. 28).Trilobed, narrower than clypeus; clithra present.Epipharynx (Fig. 34).Plegmatium absent.Corypha with 4 long setae flanked by 2-3 sensilla on each side.Haptomeral region with slightly curved, transverse row of 15-18 heli above which are 7-9 sensilla.Acanthoparia with 7-9 short, stout setae, decreasing in size posteriorly.Chaetoparia welldeveloped, covered with longitudinal rows of long, stout setae and many smaller and finer setae near the gymnoparia.Laeotorma short with pternotorma present.Dexiotorma long (1/3 length the base of epypharinx), pternotorma short or absent.Haptolachus with 4 sensilla (2 on the base, 2 on left margin).Sensorial cone present.Sclerotized plate and crepis absent.Mandibles .Asymmetrical, with 2 scissorial teeth anterior to notch; 2 posterior to notch on left mandible, and 1 poste rior to notch on right mandible.Scissorial tooth of left mandible S3 conspicuously reduced and widely separated from S4 tooth.Stridulatory area elongate-oval consisting of 24-25 transverse ridges; inter-ridge area 5 to 8 times ridge width (Fig. 36).Dorsal surface with 2 setae near the proximal end of the scissorial area and 6-7 dorsomolar setae.Basomedial angle with brustia of short setae.Max illa (Fig. 37).Galea and lacinia fused forming mala.Mala with large uncus at apex and 2 subterminal unci fused at base.Stridulatory area consisting of a row of 5-7 acute teeth and 1 small anterior conical process.Labium (Fig. 35).Hypopharyngeal sclerome with well-developed trun cate process on right side.Glossa with 3-5 setae set in 2 rows on each side; apex with 6-7 sensilla; base with transverse row of 10-14 short setae.Lateral lobe with 10-11 setae on each side.Antenna (Fig. 29).4-segmented.Apical segment with 2 dorsal sensory spots and 3 ventral sensory spots (1 lateroexternal and 1 laterointernal).

Potosia cuprea brancoi
Thorax.Dorsa of thoracic segments with 1-4 rows of short setae, each posterior row with long to short setae.Spiracle.Thoracic spiracle with 22-29 holes across diameter.Lobes of respiratory plate almost equal (Fig. 32).Legs.Tarsunguli cylindrical bearing 10-11 setae (Fig. 30).Abdomen.Abdominal spiracles similar in size.Dorsa of abdominal segments I-VIII with 3-4 rows of short setae, each posterior row with long to short setae.Abdominal segments IX-X fused, densely setose with short setae and a single row of long to short setae in the middle and at the apex (Fig. 27).Tegilla composed of short, acute setae and sparse long setae.Lower anal lip with many short and curved setae and 1 transverse row of long, acute setae (Fig. 31).Raster with a pair of palida joined anteriorly and slightly diverging posteriorly.Each palidium consisting of 14-17 pali.Apex of pali acute and flattened (Fig. 33).
Thorax.Dorsa of thoracic segments with 1-4 rows of short setae, each posterior row with long to short setae.Spiracles.Thoracic spiracle (Fig. 45) with 26-30 holes across diameter.Respiratory plate with superior lobe slightly larger than inferior lobe.
Abdomen.Abdominal spiracles similar in size.Abdominal segments I-VIII with 3-4 rows of short setae, each posterior row with long to short setae.Abdominal segments IX-X fused, densely setose with short setae and a single row of long to short setae in the middle and at the apex (Fig. 40).Tegilla composed of short, acute setae and sparse long setae.Lower anal lip with many short and curved setae and 1 transverse row of long, acute setae (Fig. 44).Raster with a pair of palida joined anteriorly and slightly or non-diverging posteriorly.Each palidium consisting of 15-19 pali.Apex of pali acute and flattened (Fig. 46).

KEY TO N. MORIO, N. OBLONGA, P. CUPREA BRANCOI AND P. OPACA THIRD INSTAR LARVAE
The following key provides the diagnostic characteris tics of the above four species.
a Occasional adult emergence EH Pupa □ Larva stage ■ Active adult ■ Dormant adult

Notes on biology
Immature stages of these species were found in organic substrates such as vegetable matter in soil surrounding root systems of plants, ant nests, rabbit latrines and wood (Table 1).Our field observations showed that P. cuprea brancoi and P. opaca occur in decaying wood of Ficus carica L., Ceratonia siliqua L. and Phoenix dactilifera L., where they consume the wood and promote more rapid decay.In contrast, Netocia species deposit their eggs in rich organic soil close to organic matter (e.g.piles of rabbit dung and piles of debris close to ant nests) and I deep inorganic soil (Table 1).
In the laboratory, P. cuprea brancoi, P. opaca and N. morio larvae feed on ripe fruit, whereas N. oblonga was unable to exploit this resource.The results showed that species feeding on ripe fruit completed their life cycle in 2-3 months (Fig. 53), and normally overwinter as an adult.In contrast, field observations showed that, in many cases, these species overwinter as larvae (Table 1).
Netocia oblonga has a life cycle of 1-2 years and over winter as larvae.

Larval morphology
The morphology of the larvae differ sufficiently to sup port the validity of genus status for both Netocia and Potosia.Characters supporting this differentiation are the shape of the pali (Figs 7,20,33,46) and the form and disposition of the scissorial teeth on left mandible (Figs 13,26,39,52).Pali are round at apex in Netocia and pointed in Potosia.The anterior frontal setae are reduced to microsetae in Potosia, Liocola, Cetonischema and Cetonia Fabricius, 1775 species (Medvedev, 1952), whereas the Netocia species described here and those illustrated by Medvedev (1952Medvedev ( , 1964)), such as N. hungarica (Herbts, 1790), N. karelini (Zoubkoff, 1829) and N. trojana (Gory & Percheron, 1833), have welldeveloped anterior setae.Netocia was traditionally sepa- rated from other related genera because the mesometastemal apófisis in adults is setose and densely punc tate.However, the systematic position of both genera remained unresolved.Our results show that larval mor phology supports the separation of both genera.
Several diagnostic characters such as the number of frontal setae, body vestiture, and the shape of thoracic spiracles distinguish N. morio from N. oblonga.On the contrary, the morphology of P. cuprea brancoi and P. opaca was very similar.Both species are parapatric and exploit the same trophic resource, and their larvae nor mally coexist.In this case, the stridulatory area of mandi bles was the most reliable character for identify both spe cies.The stridulatory area of mandibles was reported as a specific diagnostic character for closely related species, and may be related to intraspecific communication between larvae (Mico et al., 2001).

L a rv a l biology
The larvae develop in moist organic substrates such as piles of descomposing vegetable matter, packrat dung middens, or ant nests (Wheeler, 1910;Paulian, 1959;Ritcher, 1966;Janssens, I960;Hardy, 1988;Mico et al., 2000) and takes between 1-3 years.Nevertheless, there are few explicit descriptions of the larval biology of cetoniine species.Our field observations show that there are differences in the substrates exploited by the imma ture stages of the different species (Table 1).Potosia females laid their eggs in the hollows of branches and trunks of large trees.Such hollows are often full of soil and organic matter, however, larvae enter into close prox imity with live wood.Palms are very commonly planted in the Southeastern Iberian Peninsula in gardens and are important commercially, the date-palm.Palms have closed tubular leaf sheaths.In the genus Phoenix L. the dorsal portion of a sheath is thickened whereas the remainder is fibrous, and the woody dorsal portion may persist as a stub on the trunk after a leaf in shed (Tomlin son, 1990).The soil and organic matter that accumulates between the sheath and trunk is a good substrate for oviposition.In the field larva faeces occur between the sheaths and the trunks, and burrows of Potosia larvae in the woody dorsal portion of leaf sheaths.Third instar larvae were found inside the trunks.However, the injury inflicted on trees tissue was not quantified.
Potosia immature stages are not only associated with decaying wood, as the larvae of P. cuprea have been found under the large debris piles of Formica rufa L. (Wheeler, 1910).In contrast, no larvae of Netocia were found in decaying wood.We found Netocia larvae feeding in rich organic soil surrounding plant root sys tems (Cistaceae, Lamiaceae), ant nests and rabbit latrines.Larvae of N. oblonga were found associated with aban doned ant nests.In this habitat they find the moist and organic substrates necessary for their development.Larval development does not depend on living ants, how ever, as the many reports indicate the larvae are part of the entomofauna associated with debris piles of ants (Wheeler, 1910;Ratcliffe, 1976;Hardy, 1988;Deloya & Moron, 1994).The same optimal conditions occur in piles of rabbit dung.The European rabbit Oryctolagus cuniculus (L.) live in family groups, and dominant males delimit their territory daily by depositing dung latrines (Mykytowycz & Gambale, 1969;Galante & Cartagena, 1999).These piles of dung are a stable habitat rich in organic matter for larval development.The same occurs in the soil surrounding plant root systems, which are damp and rich in organic matter from the decaying leaves.
We conclude that moist accumulations of, organic matter are optimal for the development of Netocia and Potosia larvae, however, Potosia species are more gener alist, and able to feed on wood in the Southeastern Iberian Peninsula.
Under laboratory conditions, the life cycle of P. cuprea brancoi, P. opaca, and N. morio lasted a few months, and they overwintered as adults (Fig. 53).Field observations showed that the same species could overwinter as third instar larvae.Temperature and the type of food resulted in the faster development under laboratory conditions, where ripe fruit was a rich resource for P. cuprea brancoi, P. opaca, and N. morio larvae.In spite of there being no difference in the mouth parts of N. morio and N.oblonga, the latter did not feed on ripe fruit.The differ ences in the food of the larvae of Netocia species in the laboratory prevented us from comparing their life cycle durations.Studies on Scarabaeoidea show that tempera ture affects life cycle duration (Bourgin, 1946;Balachowsky, 1962;Kirk & Kirk, 1990, Vernon & Van nier, 2001), however there are no explicit descriptions of how the quality and quantity of food affect larval devel opment.

Table 1 .
Field records of the different substrates in which immature stages of Netocia and Potosia were found.