Larval morphology of some Anisopliini grain beetles with a key to their larvae (Coleoptera: Scarabaeoidea: Rutelidae: Anomalinae)

The third instar larvae of three Anisoplia species, Anisoplia baetica Erichson, 1847, Anisoplia depressa Erichson, 1847 and Anisoplia remota Reitter, 1889 are described and illustrated to show the diagnostic characters of the species. The third instar larva of the monospecific genus Anthoplia, represented by Anthoplia floricola (F., 1787) is also described and illustrated. These four species are included in a revised key to the larvae of Anisopliini, which now includes four genera, and ten species. The taxonomic status of Anthoplia based on the larval morphology, is discussed.


INTRODUCTION
The tribe Anisopliini includes a total of five genera in the Paleartic Region (Baraud, 1986): Chaetopteroplia Medvedev, 1949, Hemichaetoplia Baraud, 1986, Brancoplia Baraud, 1986, Anthoplia Medvedev, 1949, and Anisoplia Schonherr, 1817.The first three genera com prise a total of 20 species showing a circummediterranean distribution except for the Iberian peninsula.The mono specific genus Anthoplia is known from North Africa (Morocco, Algeria, Tunisia and Libya) and from almost all of the Iberian Peninsula except the Northwest (Baraud, 1992).The genus Anisoplia is the most abundant and the most widely spread genus of Anisopliini; with over 50 species, this Eurasian genus does not extend further north than the line joining Paris-Berlin-Moscow (Machatschke, 1961).
Adults of Anisopliini feed exclusively on grass pollen, whereas the larvae are polyphagous and feed on the roots of many plants.Although the larvae of many Anisopliini species have been considered as pests of several crops (Bogachev, 1946), little is known about the larval mor phology, or adult and larval biology of the tribe. Med vedev (1949) illustrated dorsal and ventral views of the last abdominal segment of Chaetopteroplia segetum (Herbst, 1783), Anisoplia (Autanisoplia) austriaca (Herbst, 1783), and Anisoplia (Anisoplia) deserticola Fischer, 1824.Few years later, Medvedev (1952) improved on the descriptions of these species and described the larvae of Brancoplia leucaspis (Castelnau, 1840), Anisoplia (Anisoplia) alazanica Zaitzev, 1918 and Anisoplia (Anisoplia) farraria Erichson, 1847, and pro vided a key to the species of Anisoplia.However, he could not separate A. alazanica from A. farraria.In the short description he gave of A. farraria he emphasized the similarity between A. farraria and A. alazanica, and did not illustrate the first species.Zacharieva-Stoilova (1962) contributed to the knowledge of Anisopliini larvae by describing and illustrating the last abdominal segment (ventral and dorsal view) and the head of Anisoplia (Ani soplia) lata Erichson, 1847 and Anisoplia (Anisoplia) agricola (Poda, 1761).However, none of these contribu tions constituted a detailed description and no more new descriptions have been published.

MATERIAL AND METHODS
A total of 10 to 20 adult specimens of each species were kept in plastic breeding cages (20 cm high, 15 cm wide) with soil and grass.The lid was an opening (6 cm in diameter) covered with a gauze screen.These breeding cages were maintained in an envi ronmental chamber at 25°C : 20°C (L : D), 80 + 5% RH, and a photoperiod of 15L : 9D.The breeding cages were examined weekly and the results recorded.
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 Collection of Ento mology of the University of Alicante, Spain (CEUA).In the description of larvae the anatomical designations of Ritcher (1966) were used.The median of some characters is presented in brackets.

Common morphological characteristics of the third instar larvae of Anisopliini.
Body.Total length 25-28 mm.Body C-shaped, arched at the level of 4th abdominal segment (Figs 1, 14).
Thorax.Size of prothoracic spiracles 0.21 mm high and 0.15 mm wide (Fig. 13); respiratory plate with infe- rior lobe conspicuously larger than superior lobe and with 8 holes across diameter at middle; holes suboval.

Abdomen.
Raster without palidium (Fig. 12); Septula defined and elongated.Area defined by the subcircular furrow of dorsum of tenth abdominal segment being about 56% of the dorsal surface of the segment.Vestiture of the SFA with isolated short and long setae, usually absent from lateral margins (Fig. 11).
Thorax.Size of prothoracic spiracles 0.28 mm high and 0.21 mm wide (Fig. 26); Lobes of respiratory plate equal; distance between both lobes as wide as diameter of spiracle or slightly narrower; respiratory plate with 8 holes across diameter at middle; holes suboval.

Abdomen.
Raster with palidium possessing two par allel rows of 6-10 ( 8) pali (Fig. 25).Area defined by the subcircular furrow of the dorsum of tenth abdominal seg ment about 43% of the dorsal surface of the segment.Vestiture of the SFA with setae equal in length on centre and apex, absent from lateral and basal margins (Fig. 24).Anisoplia remota Reitter, 1889 third instar larva.
Thorax.Size of prothoracic spiracles 0.24 mm high and 0.18 mm wide (Fig. 35); Lobes of respiratory plate equal; distance between both lobes less than diameter of the spiracle at the middle; respiratory plate with 8 holes across diameter at middle; holes suboval.

Abdomen.
Raster possessing two parallel rows of 6-8 ( 7) pali (Fig. 37).Area defined by the subcircular furrow of the dorsum of tenth abdominal segment 45% of the dorsal surface of the segment.Vestiture of the SFA with setae equal in length on centre and apex, absent from lat eral and basal margins (Fig. 36).Anisoplia depressa Erichson, 1847 third instar larva.
Thorax.Size of prothoracic spiracles 0.25 mm high and 0.17 mm wide (Fig. 46); Lobes of respiratory plate equal; distance between both lobes wider than the diameter of spiracle at middle; respiratory plate with 6 holes across diameter at middle; holes suboval.

Abdomen.
Raster without palidium (Fig. 48); Septula defined and elongated.Area defined by the subcircular furrow of the dorsum of tenth abdominal segment 56% of the dorsal surface of the segment.Vestiture of the SFA with short and long setae on centre and apex, absent from lateral and basal margins (Fig. 47).

DISCUSSION
Until now, the larval characteristic defining Anomalinae was the possession of a raster consisting of 2 monostichious palidia (Ritcher, 1966).However, the absence of a palidium in A. depressa and Anthoplia, refutes this assertion.Larvae of Anisopliini can be distinguished from other Anomalinae by the abdominal spiracles: those on I and VIII are conspicuously smaller in Anisopliini larvae.In contrast, in other Anomalinae the spiracles on abdominal segments VII-VIII are similar in size and con spicuously larger than the spiracles on I-VI (Ritcher, 1966).Of the characters used in the diagnosis of species of Anisopliini, we favour those found on the last abdominal segment and the stridulatory area of mandibles.The shape of the stridulatory area on the man dibles and the number of ridges are normally cited in descriptions of larvae (Vanin & Costa, 1980;Jameson et al., 1994), however, the width of the ridges and the width of the inter-ridge area are not normally described.In the Anisopliini larvae studied, this is a species specific diag nostic character, which may be related to intraspecific communication between larvae.In other Anomalinae, the other mouthparts, such as epipharynx and hypopharynx, are morphologically uniform, probably because of their similar feeding habits.The shape and vestiture of the SFA are very useful species specific characters and the size and shape of the SFA allows the separation of Chaetopteroplia and Brancoplia from other genera.In contrast, it is difficult to separate the genus Anthoplia from Anisoplia morphologically.In fact, only a few specific characters distinguish Anthoplia from Anisoplia depressa.Our results indicate it is not possible to separate Anthoplia from Anisoplia on the basis of larval morphology.How ever, more Anisopliini larval descriptions are needed before the phylogenetical trends in the group and the sys tematic position of the monospecific genus Anthoplia can be determined.