Delta Flower Scarab - Trigonopeltastes delta
Species epithet refers to the triangular pattern on the pronotum, which resembles the Greek letter Delta. Live adult scarab beetles photographed at Gainesville, Florida, USA.
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The delta flower scarab is also commonly known as the "D beetle." The triangle on the beetle's pronotum has been suggested as mimicry of  the markings on paper wasps in the genus Polistes. The species is diurnal, that is, it is active during daylight. Most of its activities revolve around flowers - they eat pollen and mate almost exclusively on flower blossoms.

Delta flower beetles are members of the subfamily Cetoniinae, commonly called fruit or flower chafers. There are around 4,000 species, many of them still undescribed. Masked Chafer beetle larva take the form of white grubs which live underground and do serious damage to plants, especially turf grasses, by feeding on their roots. As the grubs mature during the late summer and fall, turf damage becomes apparent as brown patches. If the infestation is severe, the grass may be pulled back like a rug, the roots being completely destroyed. Various animal predators such as crows, skunks and raccoons may further damage the lawn by digging for the grubs, a favored food. Grubs may be controlled by spike aeration if they are caught feeding close to the surface, about 45 days after the adult beetles first appear. [1]

Adult delta flower scarabs can be separated from other species by the combination of the following characteristics: epipleuron easily recognizable, border lateral of elytra sinuate and antennal insertion visible from above. Six tribes are normally recognized: Stenotarsiini, Schizorhinini, Gymnetini, Goliathini, Cetoniini, and Cremastocheilini, the last four being found in the New World. The tribe Gymnetini is the biggest of the American tribes, and Goliathini is only found in southern North America. [3]

Lawns showing damage from grubs may be treated with an insecticide. Insecticides available for homeowners include diazinon (25% EC [liquid] or 5% granular); trichlorfon (Dylox) (6.2% granular); bendiocarb (Intercept), halofenozide (GrubBGon, GrubEx), or imidacloprid (Merit, formerly GrubEx) for control of white grubs. Heterorhabditis bacteriophora nematode is an example of an alternative product for white grub control that is available. For all products, read and follow all label directions, then apply to damaged areas. Water the insecticide into the soil immediately. If treating a large area, stop after a portion has been treated and water the material in, then complete the rest of the lawn area needing treatment. Only treat in and around affected areas; grubs may only be in a small part of the lawn. Imidacloprid and halofenozide are suggested to be applied before grub damage appears. An example of a way to use these products would be to apply in July to irrigated lawns that are surrounded by dry lawns, especially when adult beetle flight is high in areas with a history of grub damage.

Spring treatment for annual white grub is not suggested since the grubs feed for a short period of time in spring and are reaching maturity, thus are not controlled easily. In addition, turf grasses are actively growing at that time so usually don’t show damage.

Other insects may attack lawns in northern Illinois but severity of damage changes from season to season and also by location. Examples include sod webworm, billbug, chinch bug, and aphids. These insects differ from grubs in that they are feeding at or above the surface of the soil and usually are not as destructive. [5]

References:
1. The University of Arizona, Maricopa County. Masked Chafer Beetle / Annual White Grub
2. Pascarella, J.B., Waddington, K.D., & Neal, P.R. 2001. Non-apoid flower-visiting fauna of Everglades
3. White, R.E. 1983. A Field Guide to the Beetles of North America. Houghton Mifflin Company, Boston. 405 pp.
4. Bugguide.net Species Trigonopeltastes delta - Delta Flower Scarab
5. University of Illinois Extension White grub problems in lawns
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Order Coleoptera: Beetles are the dominant form of life on earth: one of every five living species is a beetle. Coleoptera is the largest order in the animal kingdom, containing a third of all insect species. There are about 400,000 known species worldwide, ~30,000 of which live in North America.  Beetles live in nearly every habitat, and for every kind of food, there's probably a beetle species that eats it.
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