The family Scarabaeidae as currently defined consists of over 30,000 species of beetles worldwide. The species in this large family are often called scarabs or scarab beetles. The classification of this family is fairly unstable, with numerous competing theories, and new proposals appearing quite often. It is probable that many of the subfamilies listed here will no longer be recognized very much longer, as they will likely be reduced in status below subfamily rank, or elevated to family status (the latter is most likely, e.g., with the family "Melolonthidae" already appearing in some recent classifications). Other families have been removed recently, and are nearly universally accepted (e.g., Pleocomidae, Glaresidae, Glaphyridae, Ochodaeidae, Geotrupidae, and Bolboceratidae).
Scarabs are stout-bodied beetles, many with bright metallic colors, measuring between 1.5 and 160 mm. They have distinctive, clubbed antennae composed of plates called lamellae that can be compressed into a ball or fanned out like leaves to sense odors. The front legs of many species are broad and adapted for digging.
The C-shaped larvae, called grubs, are pale yellow or white. Most adult beetles are nocturnal, although the flower chafers (Cetoniinae) and many leaf chafers (Rutelinae) are active during the day. The grubs mostly live underground or under debris, so are not exposed to sunlight. Many scarabs are scavengers that recycle dung, carrion, or decaying plant material. Others, such as the Japanese beetle are devastating agricultural pests.
Some of the well-known beetles from the Scarabaeidae are Japanese beetles, dung beetles, June beetles, rose chafers (Australian, European and North American), rhinoceros beetles, Hercules beetles and Goliath beetles.
White grubs, grubworms or curl grubs are the larvae of scarabs. Grubs commonly attack the roots of turfgrasses and ornamental plants. Damage first appears as drought stress, such as wilting and drooping.
Heavily infested turf first appears a gray-green off color and wilts in the hot sun. Such infestations typically appear in oddly shaped and sized patches among healthy plants, creating an unsightly contrast. Continued feeding will cause the turf to die in large irregular patches.
The tunneling nature of the grubs causes the turf to feel spongy, and it is easily rolled back, since the deep roots are consumed first, exacerbating the plants' problems with drought in hot dry weather. Grub populations also attract predatory mammals such as armadillos, skunks, raccoons, opossums, and moles that can hear the grub activity and dig into the turf in search of a meal - causing further damage to the turf.
Until recently, the most common treatment in the United States was an application of an extermination chemical, such as diazinon. However, diazinon use has been discouraged by EPA in favor of chemical preservatives, which alter the taste of the roots and more specifically target grubs without affecting other insect species as does diazinon or other poisons.
Punctate flower chafers (Polystigma punctata) mating
Common June beetle (Phyllophaga sp.) found in Michigan
Used in 19th century amateur art (Bankfield Museum)
Rear view of Pachnoda sinuata
Male Milichus durandi
- RU Ehlers. Current and Future Use of Nematodes in Biocontrol: Practice and Commercial Aspects with Regard to Regulatory Policy Issues. Biocontrol Science and Technology Volume 6, Issue 3, 1996.