When fat larvae cavort in the garden and compost, the busy swarm drives worry lines on the gardener’s forehead. Now the question is whether it is a matter of beneficial insects or pests. Comparison with images makes a valuable contribution to identification. This guide explains how to accurately identify brown-headed white caterpillars.

White caterpillars are beetle larvae

Botanists call caterpillars the larvae of butterflies and some other insects, such as plant wasps. Valuable butterfly species such as swallowtail, brown bear, peacock butterfly and other beauties appear in the feeding stage as caterpillars. A green or brown body color is characteristic of butterfly larvae. Rare species catch the eye as caterpillars with a bright red body, like the shy Willow Borer butterfly, or blue-green hued silhouette, like the beautiful Blue-headed Butterfly.

In the case of white caterpillars with a brown head, on the other hand, you are confronted with beetle larvae, also known as grubs. In this form, both beneficial insects and pests can colonize your garden. The further procedure depends largely on an unequivocal identification. This guide has set itself the task of simplifying the identification of grubs using images.

Maikäfer (Melolontha)

When adult cockchafers fly out in May, they have gone through a long phase of metamorphosis as caterpillars in the soil. During a short lifespan, females lay up to 100 eggs in moist humus soil, from which the grubs hatch within about six weeks. The caterpillar stage extends over a period of up to four years. In this phase, the larvae go through different stages and gain length. This circumstance makes a well-founded determination difficult, because color and size alone do not lead to the desired result. Only the combination of the following properties leads to the right result:

  • Creamy white to yellowish body
  • Uniformly thick body shape with a length of 3 to 7 cm
  • Brown head with clearly visible mandibles
  • Strong legs with articulated kinks

For many decades, cockchafers were considered pests and suffered from drastic control measures. Adult beetles can appear en masse and devour entire deciduous forests. However, affected trees recover from a cockchafer plague within a short time. Larvae, on the other hand, feed on plant roots, which can result in widespread tree death. This applies in particular in connection with defoliation by adult cockchafers. Radical use of insecticides such as DDT has decimated the population so severely that May Beetles are treated as vulnerable by nature lovers. If you have identified the caterpillars as cockchafer larvae, there is no urgent need to take action against the caterpillars. Please carry the grubs to a secluded niche in the garden where a bit of nibbling on plant roots is allowed.

June Beetle, Ribbed Curlew Beetle (Amphimallon solstitiale)

The larvae of the June beetle often have to pay for their fatal resemblance to May beetle larvae with their lives. Distinguishing between the two types of caterpillars is a challenge even for experts. June beetles can only be distinguished from the voracious cockchafers by their smaller bodies when they are fully grown imago. As a result, the ribbed curlew beetle is now just as rare as its formerly feared relative, especially since both species of beetle belong to the scarab beetle family.

The garden beetle (Phyllopertha horticola), which is sometimes also called the June beetle, also falls into this category. Adult beetles are unpopular with home gardeners because they nibble on the flowers and leaves of rose plants. As white caterpillars with a brown head, garden chafer grubs cannot be distinguished from cockchafer larvae, especially since all other characteristics are the same.

Only the damage image gives an indication for the determination. Roots of trees and shrubs of all kinds are on the menu for cockchafer caterpillars. June beetle larvae , on the other hand, enjoy the roots of grasses and other herbaceous plants. Yellow spots in the lawn or signs of drought stress on flowers and perennials indicate the presence of June beetle grubs.

Rosenkäfer (Cetoniinae)

With their shiny metallic wings, adult rose chafers are a feast for the eyes and unmistakable. In the larval stage, however, the beetles take on the typical shape of a grub, which can lead to confusion with other beetle larvae. Rose beetle larvae are characterized by the following attributes:

  • White body with grey-black shading
  • Thicker on hind body than front
  • Tiny stubby legs with no recognizable joint crease
  • Brown head at the end of the slimmer forebody
  • C-shaped body shape in undisturbed position

The whereabouts of the caterpillars give a further indication of the correct identification. Rose beetle larvae live primarily in plant litter, mulch and decomposing wood because they primarily feed on organic waste. In the home garden, white caterpillars can often be found in the compost, where they make an important contribution to the production of humus for the natural nutrient supply in the bed. Rose beetle larvae are therefore among the beneficial insects and should not be disturbed in their important work.

Tip: Turning over and digging up compost can endanger the lives of valuable rose beetle grubs. Gather the highly visible, whitish caterpillars and keep the treasure in a box of soil while you dig into the compost heap. You then reintroduce the beneficial insects so that they continue to participate in the production of natural fertilizer.

Nashornkäfer (Oryctes nasicornis)

Dead wood is the preferred habitat of the rhinoceros beetle. The beneficial insect does not only feel in good hands in wood mulch, but also in bark mulch and compost heaps with a high proportion of fibrous wood residues. It is therefore not surprising that its larvae are frequent guests in private gardens. Welcome the rhinoceros beetle caterpillars to your green kingdom, as their robust digestive system processes organic material that is incompatible with many soil organisms. The useful grubs can be recognized by these properties:

  • Whitish to yellow with a brown head
  • Small brown spots from rump to head
  • Finger thickness, regular body shape
  • Body length of up to 10 cm

There is no cause for concern if you come across a giant rhinoceros beetle grub in your yard. The caterpillars only eat dead plant material. The former forest dwellers are threatened with extinction. According to the Federal Nature Conservation Act, killing, disturbing or removing larvae or beetles from the wild is prohibited. Please ignore offers to buy the beneficial insects, because the purchase or sale of the endangered animal species is also prohibited.

locomotion test

Despite the pictures, do you still have doubts about which beetle larvae you are dealing with? Then do the locomotion test. Place questionable grubs on a flat, smooth surface, such as a stone tile. Please step back a bit and wait until the caterpillars move. The following movement patterns can be distinguished:

  • Rose beetle larvae: lying on their backs with worm-like pulsating movements
  • Cockchafer larvae: crooked and lying on their sides
  • June beetle larvae: stretched and crawling

Please note that the locomotion test is not a scientifically based determination method, but empirical values ​​from garden practice. At least the clear demarcation of the caterpillars of the rose chafer from May and June chafer caterpillars should succeed in this way thanks to a very idiosyncratic method of locomotion that the grubs of the rose chafer use.

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