Hopper (Tri-horned treehopper) Acanthuchus trispinifer
Species: A. trispinifer
Scientific names: Acanthuchus trispinifer
Synonyms: Centrotus trispinifer, Acanthucus trispinifer, Acanthuchus gracilispinus
Common name: Tri-horned treehopper
Acanthuchus trispinifer is an tiny adventive treehopper introduced from Australia during the last century. It is now found in both the North and South Islands of New Zealand. It is the only species of a horned treehopper recorded in New Zealand.
The blackish adults have three prominent spines on the dorsal surface of the pronotum (hardened plate covering the first segment of the thorax behind the head). The bulging eyes are an orange brown colour. There are two golden patches, just behind the head and above the base of the legs. The central dorsal spine of the pronotum extends backwards as a curved ridge partially covering the wings. The black anterior wings have a few pale patches towards their tips and cover the posterior wings.
This insect is usually solitary though more than one can be seen on the same branch. They feed by sucking the plant’s sap which is high in sugars and low in other nutrients with specialised mouth parts. They have long stylets, special shaped rods which are held in the rostrum. When feeding the bug moves the tip of the rostrum to the stem on which it is sitting. The stylets are then gradually pushed into the plant and manoeuvred into the phloem (or nutrient transport vessels) of the plant.
The treehoppers excrete the excess sugary liquid, which is called honeydew. The nymphs have a long extension to the abdomen that is normally retracted into the body. When the nymphs excrete honeydew, these terminal segments are extended and they flick the honeydew droplets away from the insect.
Adults are normally sedentary but are capable of jumping strongly when disturbed.
Some of the known host plants include a variety of native and naturalised trees, shrubs and climbers. Some of the hosts are Acacia decurrens, Calystegia tuguriorum, Chrysanthemoides monilifera subsp. Monilifera, Coprosma repens, Erigeron sumatrensis, Muehlenbeckia australis, Muehlenbeckia complexa, Rubus idaeus, Ulmus parvifolia.
It is thought that the female probably inserts eggs into stems of host plants. When the nymphs hatch they are initially wingless, coloured green or grey. The nymphs are also distinctive with prominent forward pointing dorsal spines on the thorax and a long tapering body. There are five nymphal stages: each is called an instar. Nymphs go from one stage to the next by moulting, changing their skin. During moulting, the skin on the dorsal side splits and the next stage pulls itself out of the old skin. Small wing buds can be seen on the fourth and fifth instar nymphs. Adults emerge from fifth instar nymphs.
(Thanks to Landcare Research for information on this insect. Martin, NA. 2015. Three-spined bug: Acanthuchus trispinifer. Interesting Insects and other Invertebrates. NZ Arthropod Factsheet Series Number 22.)