INTERESTING INSECTS

By N A Martin (2016, revised 2018)

Schellenberg's soldier bug, Spined Predatory Shield Bug, Predatory Shield Bug

Pentatoma schellenbergii Guérin, 1831

Arma schellembergi (Guérin, 1831)

Pentatoma consociale Boisduval, 1835

Oechalia consocialis (Boisduval, 1835)

Rhaphigaster perfectus Walker, 1867

This native shield bug is present in New Zealand and Australia. Schellenberg's soldier bug is a predator that feeds on free living insects such as caterpillars and beetle larvae. It occurs in gardens and parks as well as in native ecosystems.

Conservation status: Schellenberg's soldier bug is a predator of insects in native ecosystems, in gardens and parks.

Schellenberg's soldier bug overwinters as adults that shelter in secluded places. There appears to be a single generation per year with eggs being found from December to March. Each female lays several batches of eggs. The nymphs grow into adults during summer and autumn.

The adults are 8-12 mm long; the males are slightly smaller than the females. The body and forewings have a pale background covered with dark punctures. The most striking feature are the pointed ‘shoulders’. The tip the scutellum is narrow and pale. The antennae are dark brown and the legs are pale brown. On the underside there is a long rostrum that holds the stylets used for feeding. Also on the underside is a forward pointing spine extending between the last two pairs of legs.

Several clusters of eggs are laid. The clusters are often made up of 14 or 28 eggs, one or two for each ovariole. The black eggs are usually arranged in rows. Each egg has a prominent ring of white spines on top.

The nymphs that hatch from the eggs are like small, wingless adults. There are five nymphal instars (stages). Nymphs go from one stage to the next by moulting, where the "skin" on the dorsal side splits and the next stage pulls itself out. The first instar nymphs are black and red; the black on the head, thorax and around the scent glands. The fifth instar is mainly coloured black with red on the abdomen around a central area of black. This stage has black wing buds that extend on to the abdomen.

The length of the lifecycle (time from egg to adult) varies with temperature and is faster at higher temperatures. In South Australian laboratory experiments, eggs developed from 15 to 30°C, taking 20 days at 15°C and 8 days at 20°C. At 20°C the five instars took 2.3, 4.6, 4.8, 7.6 and 11 days to complete development respectively.

Walking and flying

The nymphs and adults have six legs (three pairs) that are used for walking. The adults have two pairs of wings. The front pair is modified as covers for the hind wings. Part of the forewing is coloured brown, while the rest is membranous.

Feeding

Like other Hemiptera, Schellenberg's soldier bug has sucking mouth parts. The long stylets, special shaped rods, are held in the rostrum. Schellenberg's soldier bugs are predators. The feed on free living insects such as caterpillars which they stab with their stylets, mandibles and maxillae. During feeding the insect is held by at the end of the rostrum the mandibles. The maxillae are inserted further into the prey. They form two tubes, a narrow duct down which saliva is pumped into the prey, and a larger tube up which the partly digested food is sucked.

The first instar nymph is the only stage that is not a predator. After hatching they stay by their eggs. They will probably drink water and may feed on plant juices.

Adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2BCP]

Underside of adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae), note the forward pointing spine between the last two pairs of legs. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2BCM]

Underside of adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae), note the forward pointing spine between the last two pairs of legs. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2BCN]

A mating pair of adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLW]

Underside of a mating pair of adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae): note how the pair are joined. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLX]

Side view of a mating pair of adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae): note how the pair are joined. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLV]

Eggs of Schellenberg's soldier bug, Oechalia schellenbergii (Hemiptera: Pentatomidae). Creator: JW Endt (DSIR). © New Zealand Journal of Science (1964), 7(4): 536-554, Figure 3B, page 540. [Image: 2BCV]

Eggs of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae): note the long white ‘spines’ around the top of each egg. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLT]

First instar nymphs on an egg batch of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KM0]

First instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae) that is about to moult (change skins) into a second instar (stage). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KM2]

Second instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KM1]

Underside (left) and upper side (right) of a third instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLZ]

Underside (left) and upper side (right) of a fourth instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLY]

Upper side (left) and underside (right) of the moulted skin of a fith instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLU]

Fifth instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2BCL]

Adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2BCQ]

There are several species of Pentatomidae in New Zealand that have dark coloured adults. Schellenberg's soldier bug adults have a distinctive triangular shape with obvious lateral points on the pronotum, the first segment of the thorax. The underside of an adult also has a pale forward pointing spine between the last two pairs of legs.

The black eggs have distinctive relatively long white spines on top. The last stage nymph is mostly black with bright red on the abdomen around a black middle area.

Adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2BCP]

Underside of adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae), note the forward pointing spine between the last two pairs of legs. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2BCM]

Eggs of Schellenberg's soldier bug, Oechalia schellenbergii (Hemiptera: Pentatomidae). Creator: JW Endt (DSIR). © New Zealand Journal of Science (1964), 7(4): 536-554, Figure 3B, page 540. [Image: 2BCV]

First instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae) that is about to moult (change skins) into a second instar (stage). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KM2]

Second instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KM1]

Underside (left) and upper side (right) of a third instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLZ]

Underside (left) and upper side (right) of a fourth instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KLY]

Fifth instar nymph of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2BCL]

No predators or pathogens are known.

Parasitoids

Eggs of the Brown soldier bug may be parasitized by three species of tiny wasps. Two belong to the family Platygasteridae. Trissolcus oenone (Dodd, 1913), a native species, parasitizes several native shield bugs. Another egg parasitoid, Trissolcus basalisi (Wollaston 1858), was released into New Zealand in 1949 to control the green vegetable bug, Nezara viridula. It also parasitizes eggs of other shield bugs including the Brown soldier bug. When this wide host range was discovered in the 1960s, it was regarded as beneficial, because at that time protection of crops was regarded as more important than protecting native insects. Eggs of other pentatomid species parasitized by T. basalis turn black.

The third, an unnamed species, belongs to the genus Acroclisoides sp.in the family Pteromalidae. It has distinctive black spots on its forewings.

Eggs of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae) that have been parasitised by Acroclisoides sp. (Hymenoptera: Pteromalidae): note the exit holes made by the adult wasps in the top of the egg shells. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2S4T]

Dead and live adult Acroclisoides sp. (Hymenoptera: Pteromalidae) after emerging from eggs of Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2S4U]

The Schellenberg's soldier bug feeds on a variety of free living prey notably caterpillars and beetle larvae.

Feeding

Like other Hemiptera, the Schellenberg's soldier bug has sucking mouth parts. The long stylets, special shaped rods, are held in the rostrum. They stab their prey with their stylets, mandibles and maxillae. During feeding the insect is held by at the end of the rostrum the mandibles. The maxillae are inserted further into the prey. They form two tubes, a narrow duct down which saliva is pumped into the prey, and a larger tube up which the partly digested food is sucked. The first instar nymph is the only stage that is not a predator.

Adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2BCQ]

Adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae) feeding on a caterpillar. Creator: Tim Holmes. © Plant & Food Research. [Image: 2BCR]

Adult Schellenberg's soldier bug, Oechalia schellenbergii (Hempitera: Pentatomidae) feeding on a caterpillar. Creator: Tim Holmes. © Plant & Food Research. [Image: 2BCS]

Why Stink bugs

Pentatomidae are often called stink bugs because when handled they emit a strong smell. The nymphs have prominent glands on the upper (dorsal) side of their abdomen, while adults have glands between the bases of their legs. The chemicals may deter predators and cause other bugs to drop to the ground, but some of the chemicals produced may also act as aggregation pheromones.

Research project

Do first instar nymphs imbibe surface liquid on plants and/or suck plant juices?

Awan MS. 1988. Development and mating behaviour of Oechalia schellenbergii (Guerin Meneville) and Cermatulus nasalis (Westwood) (Hemiptera, Pentatomidae). Journal of the Australian Entomological Society 27: 183-187.

Cumber RA. 1964. The egg-parasite complex (Scelionidae: Hymenoptera) of shield bugs (Pentatomidae, Acanthosomidae) in New Zealand. New Zealand Journal of Science. 7: 536-554.

Edwards PB, Suckling DM. 1980. Cermatulus nasalis and Oechalia schellenbergii (Hemiptera: Pentatomidae) as predators of Eucalyptus tortoise beetle larvae, Paropsis Charybdis (Coleoptera: Chrysomelidae) in New Zealand. New Zealand Entomologist. 7(2): 158-164.

Lariviere M-C. 1995. Cydnidae, Acanthosomatidae, and Pentatomidae (Insecta: Heteroptera): systematics, geographical distribution, and bioecology. Fauna of New Zealand. 35: 1-107.

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

1 August 2018, NA Martin. Parasitoid list updated, photos of Acroclisoides sp added

1 August 2017, NA Martin. Additional photographs of eggs and nymphal instars added. Two photos of possible nymphs removed.

12 December 2016. NA Martin. Natural Enemy Table: biodiversity information corrected.