The Golden Scarab: A Beneficial Larva for Composting
In our gardens, there is a unique creature that plays a crucial role in the composting process – the Golden Scarab larva. Also known as the Cetonia aurata, this beautiful beetle is commonly found across Europe and is recognizable by its striking metallic green color. Often referred to as the “rose chafer,” the Golden Scarab larva may occasionally be seen sunning itself on a step or any sunny surface in your garden. But it is the larva of this beetle that proves to be a valuable ally in composting, contributing to its enrichment. Let’s take a closer look at the Golden Scarab larva and its importance in composting.
Who is the Golden Scarab?
The Golden Scarab belongs to the order Coleoptera and the family Scarabaeidae. This beautiful beetle, with its iridescent green color and golden reflections, is commonly found in France and throughout Europe. The coloration can vary within regions, with shades of blue, purple, black, or red being more pronounced. As an adult, the Golden Scarab measures between 12mm and 20mm in length, and sometimes even up to 25mm.
The Golden Scarab has a pair of membranous wings, which are invisible when the beetle is at rest as they are covered by its wing cases, or elytra. These elytra can be smooth or slightly velvety with tiny whitish spots. When the beetle flies, the elytra do not pivot but move slightly to allow the wings to pass through.
It is challenging to differentiate male and female Golden Scarabs at first glance. However, if you observe a line along the length of the insect’s belly, it indicates that it is a male. The male’s reproductive organ, resembling a penis, is usually well-developed but may not always be clearly identifiable.
Golden Scarab or Chafer Beetle: How to differentiate the white larvae?
It is essential to differentiate between the larvae of the Golden Scarab and the chafer beetle to preserve the beneficial Golden Scarab larva. While the white chafer larvae live in the soil and feed on plant roots, often causing damage to plants, the Golden Scarab larva does not harm plants and instead helps improve compost. Aside from their different habitats, several physical characteristics can help distinguish the white larvae:
- The chafer larva has a large head with strong mandibles and a smaller rear end, while the Golden Scarab larva has a small head and a more developed rear end.
- The chafer larva appears more yellowish compared to the more grayish Golden Scarab larva.
- The chafer larva is smooth, whereas the Golden Scarab larva is velvety.
- The chafer larva has longer and more developed legs than the Golden Scarab larva, which has insignificant legs.
- When moving, the chafer larva crawls sideways, while the Golden Scarab larva moves on its back, aided by its stiff hairs.
A Hibernating Beetle
The Golden Scarab emerges from hibernation as the sun reappears after the cold season. It can be observed from April to the end of summer, as it enjoys basking in the sun.
A Particularly Floral Diet
The adult Golden Scarab primarily feeds on flowers, especially roses, hence its nickname “rose chafer.” In the garden, it also appreciates ripe fruits and the flowers of lilac, fruit trees, pyracantha, privet, as well as thistle, elderberry, and wild rose. This active little beetle also contributes to flower pollination. However, some gardeners may not appreciate the Golden Scarab as it feeds on flower stamens, potentially sterilizing them.
The Golden Scarab larva, on the other hand, is saproxylic, which means it feeds on highly decomposed wood. Its role is essential in the sylvigenetic cycle.
Reproduction and Life Cycles of the Golden Scarab
The Golden Scarabs engage in multiple mating sessions, which result in egg-laying occurring around May and June. After laying eggs, the female dies. However, shortly after, between late June and early July, the eggs transform into larvae that are particularly beneficial to the garden, giving rise to a new cycle.
As mentioned, the Golden Scarab larva feeds on highly decomposed wood. It thrives in hollow trees, stumps, and decaying wood. However, this food source provides little nutrition, so the larva takes a long time to develop, usually between two to three years. When ready, it constructs a cocoon made of wood fibers and soil for pupation.
As an adult, or imago, the Golden Scarab can be observed from April to October. Typically, two generations occur in a single year. The spring generation nourishes mainly on pollen, lays eggs in June, and then dies. The autumn generation feeds primarily on fruits before hibernating and laying eggs the following summer.
The Golden Scarab Larva: An Ally in the Garden
The Golden Scarab larva exclusively feeds on the waste present in the compost pile. By actively participating in the decomposition process, it helps create high-quality compost. Like other decomposers in the macrofauna category, the Golden Scarab larva breaks down dead or decomposing organic matter into even smaller debris. The compost provides an excellent nutritional source for the larva, which enriches it through its actions. Additionally, the larva’s organic matter cocoon, created for pupation, further enhances the nutritional value of the compost.
These valuable allies can measure between 3cm and 4cm and remain in the larval stage for 2 to 3 years before transforming into adults. As mentioned, they pose no threat to your garden plants, unlike the chafer larva. It is therefore crucial, once again, to be able to recognize them.
Whether in larval or adult form, the Golden Scarab proves to be a useful ally in the garden. It plays a role as a decomposer in composting and also contributes to flower pollination, despite the marginal damage it may cause as an adult.
Unfortunately, the felling of dead trees and their removal from forests impact the Golden Scarab population, leading to a decline in their numbers. Yet, this insect is a valuable player in the natural cycle of tree life and various plant species.
You can take action at your level by protecting the Golden Scarab and avoiding the destruction of its larvae. When using compost for your plantings, remove them – without harming them, of course – and place them in the remaining compost or another food source. This precaution helps prevent too many larvae from living in a pot or planter that may be too small to support them all adequately. Otherwise, they would quickly deplete their food resources and eventually perish.
