INTERESTING INSECTS

By N A Martin (2017)

Daisy tree leaf beetle

This endemic leaf beetle is found in the North and South Islands. Adult beetles feed on leaves and based on leaf damage symptoms, this beetle is common in the Auckland region on its host plants, Brachyglottis and Olearia species, especially Brachyglottis kirkii and Olearia rani.

Conservation status: Widespread in native ecosystems.

Adults are found feeding on young leaves in late spring and early summer. It is presumed that eggs are laid in the soil and that larvae feed on plant roots and pupate in winter or early spring.

Adults are typical beetles, each with six legs and hard wing covers (elytra). They are small, about 4 mm long. They have pale grey-brown wing covers with a dark brown line down the centre line. The head and legs are also a dark brown. The underside of the beetle is almost black with a pale brown ‘neck’ and areas between the prothroax (first leg segment) and the next leg segment. The terminal gentital area is medium brown. Their wings, which are longer than the wing covers, are kept safely folded up under the wing covers, except when needed for flying. When disturbed the beetles tend to drop to the ground.

Nothing is known about the eggs, larvae or pupae of this beetle.

Feeding

Adults have chewing mouth parts. They feed on young leaves of some Brachyglottis and Olearia species such as Brachyglottis kirkii and Olearia rani. The adult beetles chew holes in young leaves making a hole in the leaf or just damaging one side. Beetles probably mainly feed at night. During the day they hide on the food plant or nearby.

The distinctive colour, shape and size of the adult daisy tree leaf beetles is similar to that of other species in the genus Adoxia. The species can only be conclusively identified by an expert. However, where the adult host plants are known, it is likely that a beetle of this appearance on the host plant is the species associated with the plant.

The distinctive leaf damage on its favoured host plants, Brachyglottis kirkii and Olearia rani indicates the presence of this beetle in the habitat.

Similar leaf damage on Olearia furfuracea may be caused by adults of another chrysomelid beetle in the genus Eucolaspis. These beetles are dark brown.

No pathogens or parasitoids of the daisy tree leaf beetle are known.

Predators

One predator has been recorded. Podagritus (Parechuca) parrotti (Leclercq, 1955) (Hymenoptera: Crabronidae) is a predatory wasp. The adult female constructs burrows in soil. She hunts adult beetles, including daisy tree leaf beetles, and puts them in cells in the burrow and lays an egg on the beetle. The wasp larva feeds on the beetle and pupates in the cell.

Daisy tree leaf beetles are probably also preyed upon by other predatory insects, birds, and spiders.

Adult daisy tree leaf beetle feed on young leaves of some Brachyglottis and Olearia species (Compositae). In Auckland the main host plants are Brachyglottis kirkii and Olearia rani. Other occasional host plants are Brachyglottis repanda and Olearia furfuracea.

Plant damage

The adult weevils feed on young leaves. They chew holes in leaves from either the underside or upper side. They can remove most of the tissue from very young leaves. When the leaf damage is recent there may be black faecal dropping on the leaves.

Table: Host plants of the Daisy tree leaf beetle, Adoxia vulgaris (Coleoptera: Chrysomelidae) from Plant-SyNZ database (29 December 2016). The reliability score shows the quality of evidence for the host association (1-10, 10=high).

Common Name(s)	Scientific Name	Family	Reliability Index	Biostatus
Forest tree groundsel, Kirk's daisy, Kohuhurangi, Kohukohurangi, Kohurangi, Kōkohurangi, Orōro, Tapairu	Brachyglottis kirkii (Kirk) C.J.Webb	Compositae	10	endemic
Bushman's friend, Kōuaha, Pukapuka, Pukariao, Puke-rangiora, Rangiora, Raurākau, Raurēkau, Whārangi, Whārangi-tawhito	Brachyglottis repanda J.R.Forst. & G.Forst.	Compositae	7	endemic
Akepiro, Kūmara-kai-torouka, Tanguru, Wharangi-piro	Olearia furfuracea (A.Rich.) Hook.f.	Compositae	8	endemic
Akewharangi, Heketara, Ngungu, Taraheke, Tātaraheke, Wharangi-piro	Olearia rani (A. Cunn.) Druce	Compositae	10	endemic

Research project

The food plants of adults of this and some other chrysomelid beetles are known, but the egg laying site and food of the larvae is 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.

Harris AC. 1994. Sphecidae (Insecta: Hymenoptera). Fauna of New Zealand. 32: 1-106.

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.