Aspidiotinae, Ferris, 1942

Wappler, Torsten & Ben-Dov, Yair, 2008, Preservation of armoured scale insects on angiosperm leaves from the Eocene of Germany, Acta Palaeontologica Polonica 53 (4), pp. 627-634 : 629-631

Aspidiotinae gen. et sp. indet. 3

Material.— FIS SM.B.Me 3468. An incomplete preserved pinnate leaf (“feather−leaved”) of a lepidocaryoide palm, most probably belonging to the genus Phoenicites ; found in Messel pit near Darmstadt, Hesse, Germany.

Description.—We observed on lower surface of one leaf about 120 circular scale covers, diameter 0.317 –0.439 mm. The smaller size of the scale covers, and the structure of its concentric rings, as compared to Aspidiotinae gen. et sp. indet. 2, suggest that Aspidiotinae gen. et sp. indet. 3, includes the scale covers of nymphal stages that we regard as belonging to a separate species. The crowded population (Fig. 1K) resembles heavy infestations of the extant species Parlatoria blanchardi Targioni Tozzetti, 1892 (Fig. 1L), which is a common pest of date palms in North Africa and the Middle East ( Ben−Dov and Miller 2007).

Comments.—Palms constitute one of the most familiar and most easily recognized plant families. They are distinguished from most other angiosperms by distinctive leaves, or fronds, and they constitute one of the few monocotyledonous plant families with arborescences ( Howard et al. 2001). Palms are essentially tropical plants, of which about 75% of the species occur within rainforest ( Dransfield 1978). Additionally, there is a marked dissimilarity between the palm floras of the Old and New World. The lepidocaryoid palms (resembling the Messel specimen) are Old World taxa, except for Lepidocaryum , Mauritia , and one species of Raphia in the New World ( Tomlinson 1979).

The Arecaceae , of all identifiable monocotyledons, display the richest fossil records, as revised by Harley (2006). By the late Cretaceous, all major palm fossil categories are present. Therefore it seems unsubstantiated that insect−palm relationships are so little known and reported in the fossil record because multitude of different insect families use palms as a reliable source of food ( Howard et al. 2001; Labandeira et al. 2007). One reason could be that the insect fauna of about 85% of palm genera is completely unknown ( Lepesme 1947) and knowledge of insect−palm relationships is overwhelmingly derived from studies of three economically important palms, oil palm ( Elaeis guineensis ), coconut ( Cocos nucifera ), and date palm ( Phoenix dactylifera ), and not from wild palms (Howard 2001). There may be other reasons particular to palm anatomy or biology, but they are conjectural. These include (1) that the thicker adaxial (“upper”) wax layer on most fronds is more difficult for insects to penetrate than equivalent layers in other plants; (2) that for insects using nectar or pollen, most palm species flower only during a limited time interval of the year, restricting the spectrum of available pollinators; (3) in the absence of cambium or bark, palms are not attacked by cambium borers or bark beetles; and (4) roots of palms are not a prime target of attack by arthropods because they are not centres of carbohydrate storage (see Howard 2001).

The majority of fossil palms cannot be determined below family level, due to lack of distinctive morphological variations in foliar organs. This is especially correct regarding the genus Phoenicites , to which very likely belong the fossil specimens recorded here. Read and Hickey (1972) redefined the fossil genus Phoenicites and suggested that Phoenicites should, henceforth, be reserved or applied to non− Phoenix −like pinnate leaves.