Coprosma flea beetle - Trachytetra rugulosa
By N A Martin (2017)
Biostatus and Distribution
This small endemic flea beetle is found in both the North and South Islands where its host plants, Coprosma species (Rubiaceae), grow. Adult beetles feed on young leaves in winter and spring.
Conservation status: Widespread in native ecosystems, common in the Auckland region.
Life Stages and Annual Cycle
Adults are found feeding on young leaves in winter and spring. It is presumed that eggs are laid in the soil and that larvae feed on plant roots and pupate in the winter.
Adults are typical beetles, each with six legs and hard wing covers (elytra). These beetles are about 2.5 mm long. The dorsal (upper) side of the thorax (middle body section) and the elytra are medium brown. The elytra have darker areas. These dorsal areas are covered in punctures. Their wings, which are longer than the wing covers, are kept safely folded up under the wing covers, except when needed for flying. The last pair of legs have enlarged femurs that enable the beetle to jump, hence the name flea beetle. This species is wingless (Kuschell 1990).
Nothing is known about the eggs, larvae or pupae of this beetle.
Adults have chewing mouth parts. They feed on young leaves of Coprosma species. Adult beetles chew small holes in leaves. On thicker leaves they mainly chew from the underside, but do not eat right through the leaf, leaving the skin (epidermis) on the far side of the leaf intact, so creating a ‘window’. Beetles probably feed mainly at night but can be found feeding on leaves during the day.
There are many kinds of beetles in New Zealand. They can only be conclusively identified by an expert. Several small brown beetles may be found feeding on young leaves of Coprosma species, but the Coprosma flea beetle is the only one with enlarged femurs on their hind legs.
The presence of this kind of leaf damage in young leaves on Coprosma species in winter and spring is most likely to be caused by the Coprosma flea beetle, but could also be caused by weevils with seed feeding larvae, Praolepra species (Curculionoidea: Curculionidae). These beetles have a long ‘snout’ and do not have enlarged hind femora.
No natural enemies of the Coprosma flea beetle are known. They are probably preyed upon by birds, spiders and predatory insects.
Adult Coprosma flea beetles feed on young leaves of Coprosma species (Rubiaceae).
They mainly feed on young leaves. Adult beetles chew small holes in leaves. On thicker leaves they mainly chew from the underside, but do not eat right through the leaf, leaving the skin (epidermis) on the far side of the leaf intact, so creating a ‘window’. Beetles probably feed mainly at night but can be found feeding on leaves during the day.
|Common Name(s)||Scientific Name||Family||Reliability Index||Biostatus|
|Tree coprosma, Mamangi, Māmāngi||Coprosma arborea Kirk||Rubiaceae||8||endemic|
|Thin leaved coprosma, Aruhe||Coprosma areolata Cheeseman||Rubiaceae||8||endemic|
|Kākawariki, Kanono, Kapukiore, Karamū-kueo, Kueo (fruit), Manono, Pāpāuma, Raurēkau, Toherāoa||Coprosma grandifolia Hook.f.||Rubiaceae||10||endemic|
|Shining karamu, Kākaramū, Kākarangū, Karamū, Kāramuramu, Karangū, Patutiketike||Coprosma lucida J.R.Forst. & G.Forst.||Rubiaceae||10||endemic|
|Large seeded coprosma, Kākaramū, Kākarangū, Karamū, Kāramuramu, Karangū||Coprosma macrocarpa Cheeseman||Rubiaceae||10||endemic|
|Taupata||Coprosma repens A.Rich.||Rubiaceae||9||endemic|
|Twiggy Coprosma||Coprosma rhamnoides A.Cunn.||Rubiaceae||7||endemic|
|Glossy karamu, Kākaramū, Kākarangū, Karamū, Kāramuramu, Karangū||Coprosma robusta Raoul||Rubiaceae||10||endemic|
|Round-leaved coprosma||Coprosma rotundifolia A.Cunn.||Rubiaceae||10||endemic|
|Wavy-leaved coprosma||Coprosma tenuifolia Cheeseman||Rubiaceae||10||endemic|
The food plants of adults of this and some other chrysomelid beetles are known, but the egg laying site and food of the larvae are unknown. A simple and useful research project would be to collect adults and allow them to mate and lay eggs in pot plants of potential larval host plants. If the larvae can be reared and pupate then it would also be possible to describe the larvae and pupae. The potential host plants tested should include known adult host plants, closely related species and other plants growing in habitats where adults were present.
Kuschel G. 1990. Beetles in a suburban environment: A New Zealand case study. DSIR Plant Protection Report. No. 3: 1-118.
Samuelson GA 1973. Alticinae of Oceania (Coleoptera: Chrysomelidae). Pacific insects monograph 30: 1-165.
Dr Willy Kuschel and Dr Rich Leschen, who identified the adult beetles.
The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.