Hylamorpha elegans

Hylamorpha elegans has a distinct appearance due to its long body, usually measuring between 11.8 to 18.2 millimetres (0.46 to 0.72 in) long, and 5.8 to 10.8 millimetres (0.23 to 0.43 in) wide across the shoulders. Its head, pronotum, and elytra (wing covers) can range from light to dark green, sometimes with shiny silver or bronze reflections, and rarely orange. Chemicals used in preservation of specimens can turn the elytra blue, red, orange, or purple. Males' front legs are usually green or light brown. While females' front legs are mostly light brown, their back legs are green like their bodies. Male beetles have all green legs with a shiny appearance, especially on the middle and back legs, while females have green legs with varying degrees of shine. The ends of their protibial teeth are always black. The beetle's heads are densely covered with small bumps or dots. Its antennae have ten segments, with the final segment longer in males than in females. Their mandibles are triangular and end in a sharp or rounded point. Its back has tiny bumps or dots, and its sides have a small edge. The back legs and the lower body have long white hairs. The front legs have three small teeth at the end, and the back legs have a bump on the outer edge. The bottom part of the legs have small bumps, and the very last part of the body is slightly curved, both in males and females.

Similar to other scarab beetles, they likely rely on thermo- and hygrosensitive sensilla to assess their surroundings. Four types of sensilla are present on the antennae of Hylamorpha elegans—sensilla chaetica, which are likely to be mechanoreceptors, sensilla trichoidea, sensilla placodea, and sensilla coeloconica, which may respond to humidity and temperature. Adults typically emerge from the ground during the spring and summer when evenings are warmer.

The beetle poses significant challenges for both humans and livestock in Central and Southern Chile and Southwestern Argentina. The larvae of these beetles inflict severe agricultural damage by feeding on the roots of grasses and small grain cereals in Chile. The beetle is also a significant pest in berry crops and common hazel orchards, reducing crop yields and forage availability. Livestock grazing on pastures infested with these larvae may also experience indirect effects. Damage to pasture plants' roots can lead to reduced forage availability and quality, affecting livestock nutrition and productivity. Additionally, irregular outbreaks of H. elegans larvae in grasses and small grain cereals can be challenging for farmers and ranchers in maintaining viable pasturelands and cereal crops. Additionally, their adult counterparts occasionally cause extensive defoliation on secondary host plants, particularly species of Nothofagus trees such as Nothofagus antarctica, betuloides, dombeyi, and obliqua. These adult beetles often congregate, feed, and mate in the canopy of these trees. This defoliation can result in the death of young trees. The use of semiochemicals, such as pheromones and kairomones, for pest management has been poorly developed, adding to the challenge of mitigating their impact. …

Hylamorpha elegans exhibits a broad diet encompassing various plant parts, making it a significant agricultural pest. In its larval stage, this beetle primarily feeds on the roots of grasses and small grain cereals, leading to severe agricultural damage in Chile. Adult beetles feed on Nothofagus species, mainly N. antarctica, N. betuloides, N. dombeyi and N. obliqua. Occasionally they will defoliate host trees, and young trees can be killed by large numbers of beetles feeding on them.