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Chafer biology

Scarabaidae is a very large, diverse, cosmopolitan family consisting of several well-defined subfamilies including about 1600 genera and 27000 species (Scholtz & Grebennikov 2005). The phytophagous pleurostict Scarabaeidae (Chafers) are characterized by having most of the abdominal spiracles situated not on the pleural membrane between the tergites and sternites but on the upper portion of the sternites. They are thus separated from the laparostict scarabs like the dung beetles which predominantly feed on animal-derived food such as dung or hide. Although further usable as a diagnostic feature, the current taxonomic classification does no longer recognize the distinction between Pleurosticti and Laparosticti because the position of the abdominal spiracles is not a consistent character.

Members of Scarabaeidae show a great diversity in shape, coloration, and sculpture (Crowson 1981). The scarabs are often large and stout, oval or elongated, usually more or less convex, varying considerably in size (Body length approximately 2 to 150 mm) and mainly characterized by the shape of the antennal tips. The terminal antennomeres are expanded into plate- or leaf-like structures (lamellae) and are equipped with chemosensory sensilla. The lamellae are movable and are spread apart or close together to form a compact terminal club.

The anterior coxal cavities are large, transverse, and closed behind. The abdomen has normally six or seven visible ventral segments with the pygidium usually exposed. The legs are fossorial but variable with strong lateral teeth on the protibia. All tarsi are composed of five tarsomeres.

Some species show distinct structural sexual dimorphism with regard to the number, shape or size of horns, tubercles or similar projections on the head or pronotum. In most genera, including Anomala Samouelle, 1819, Adoretus Laporte, 1840, Holotrichia Hope, 1837, or Maladera Mulsant & Rey, 1871, it is difficult to differentiate between males and females because of their structural similarity. In most cases, the sexes may then be separated by slightly different structures of the pygidium.

Larvae have a well-developed yellow to reddish-brown sclerotized head, C-shaped bodies, usually three pairs of thoracic legs, a 10-segmented abdomen, spiracles on the mesothorax (and rarely on the prothorax) and on the first eight abdominal segments. The pupae occur usually in the normal habitat of the larvae, some are enclosed in a cell composed of surrounding materials.

Chafer adults are generalist herbivores and feed predominantly on leaves, flowers, and pollen. For some species (e.g. Maladera castanea Arrow, 1914) more than 100 different host plant species have been reported, and the number of preferred food plants with succulent roots still amount to 30 for this taxon (Tashiro 1987).

Many chafer species have an inconspicuous dark or brown colour. Most are nocturnal and hide underground during the day. At dusk the beetles come to the surface and feed on nearby plants. Low temperatures and rainfall may reduce flight activities significantly (Mishra & Singh 1999). Several chafers like the often conspicuously coloured rose chafers (Cetoniinae) or Popillia spp. (Rutelinae) are active during daytime.

The larvae are subterranean feeders of decaying plant material (inclusive of rotten wood) in organic soil and they feed on the roots and rhizomes of living plants (Ritcher 1966). The larvae of Maladera spp. feed mostly at a depth of 5 to 8cm below the soil surface (Tashiro 1987).

Beetles of similar morphological characters must not necessarily show similar physiological features such as ecological preferences or the duration of the life cycle. The life cycle depends on the species and the climatic conditions and can last between several weeks and several years (Tashiro 1987, Honomichl 1998). Some smaller species in particular seem to have shorter life cycles reproducing twice or more a year. In the northern hemisphere many chafers overwinter in the larval stage, mainly the third instar, by migrating into deeper soil layers, but through subtropical to tropical areas the life cycle patterns change considerably. For most taxa we have very little or no biological information.





   © 2008 by Dirk Ahrens •