Close window

RHOPALIDAE Scentless Plant Bugs

Image: Leptocoris rufomarginatus


Leptocoris rufomarginatus

The Rhopalidae or scentless plant bugs are a cosmopolitan family of coreoid bugs comprising roughly 18 genera and 209 species. (Australian Biological Resources Study, DEH)

In Australia Rhopalidae includes Lepticoris spp (Soapberry bugs) - seed-eating predators of Australian sapinds, notably Alectryon spp. Along the eastern coast the long beaked form of Leptocoris tagalicus occurs on at least 10 plants including non-native environmental hosts Cardiospermum (Balloon Vine) and Koelreuteria (Golden Rain Tree). Inland, it has a shorter beak and occurs on Atalaya hemiglauca. Leptocoris mitellatus is is found mostly in the southern half of the continent on Alectryon oleifolius. (1)

Image: Leptocoris tagalicus adult (beak)


Bug
Photo: Robert Whyte

Adults (coastal form) of Leptocoris tagalicusare usually orange-red and black with a long beak which they use to pierce the seed and inject salivary enzymes used to digest their food. Legs and antenna are black.

This specimen was on a Rhodamnia rubescens. Note the long beak.

Image: Leptocoris tagalicus adult (side on)


Bug
Photo: Robert Whyte

L. tagalicus is similar to L. mitellatus, found further south, but has more uniform coloration and noticeably more slender "necks" (anterior thorax) and heads than does mitellatus. L. mitellatus is more polychrome, has more prominent red eyes, and is rather neckless. Mitellatus spends a lot of time on the ground.

Image: L. tagalicus adults and nymphs


Photo: Scott Carroll
Photo: Scott Carroll

L. tagalicus that grew up on seeds of the Alectryon tomentosus trees in Sherwood Forest Park. Shown are fifth (last) stage (instar) nymphs and their freshly molted fellows. They will remain densely aggregated for about a day after the moult, until their soft exoskeletons harden sufficiently to make walking safe and flight possible.

Image: L tagalicus & L. rufomarginatus


Leptocoris spp
Photo: Scott Carroll

L tagalicus adult female and three lovely L. rufomarginatus nymphs feeding from a globe of fresh Elattostachys xylocarpa seeds on Mt. Stradbroke west of Brisbane.

Image: Leptocoris rufomarginatus adult


Leptocoris rufomarginatus
Photo: Robert Whyte

The genus includes L. rufomarginatus, a beautiful red-eyed bug with white sections on a brilliant red abdomen, and a silvery, blue-grey, green-grey section on its wings. L. rufomarginatus has been verified as feeding on Jagera psuedorhus, previously not confirmed as a host plant, in observations by Robert Whyte and Michael Mathieson in late November 2006 at Enoggera Creek, The Gap, adjacent to the cricket nets on the ovals of the The Gap SHS.

Image: Leptocoris rufomarginatus adult, one newly emerged


Leptocoris rufomarginatus
Photo: Robert Whyte

Leptocoris rufomarginatus is an impressive bug.

Compared with the other species, L. rufomarginatus is long-winged, narrow-bodied and a ready flier. It is relatively restricted to the far eastern and northern moist subtropics and tropics (Carroll et al).

When the bugs finish their last moult to become adults, they are bright red and soft.

Scott Carroll writes: "This species is really quite volant and arboreal, [with a] streamlined, deep-bodied, long-limbed morphology ... They are the most widespread soapberry bug- SE Asia N. to southern Japan, E all the way to the Tuamota Archipelago in the eastern Society islands." (private email).

Image: Leptocoris rufomarginatus adults and nymphs


Leptocoris rufomarginatus
Photo: Mark Crocker

These bugs were on a Diospyros fasciculosa below their probably host plant Jagera pseudorhus.

Scott Carroll writes: "We inspected Jagera pseudorhus for bugs between Northern Rivers and Cape York, and found none, but it has always looked like a good host to me ... it is unlikely that these bugs have crawled far from where they fed (photos show last instar nymphs and teneral adults).

Image: Leptocoris rufomarginatus Two adults at different stages


Leptocoris rufomarginatus
Photo: Robert Whyte

The more mature adult has distinct colouration including the blue grey section of wing, and you can just see the white sides to the abdomen. These bugs are spectacular in flight, as the brilliant red abdomen is exposed.

Image: Leptocoris rufomarginatus (closeup)


Leptocoris rufomarginatus

Very few visual resources exist online for these bugs as of November 2006. Most pictures in a Google image search show Leptocoris trivittatus, a New World species

The extent of the literature at this time is pretty much the Carroll et al paper (1) Ecology of Leptocoris Hahn (Hemiptera: Rhopalidae) soapberry bugs in Australia Scott P Carroll, Jenella E Loye, Hugh Dingle, Michael Mathieson and Myron P Zalucki, Australian Journal of Entomology, (2005) 44, 344-353)

Observations are ongoing.

Image: Leptocoris rufomarginatus

L. rufo
Photo: Scott Carroll

Leptocoris rufomarginatus, surveying the possibilities from the outer edge of an Alectryon tomentosus leaf in Brisbane.

Image: Leptocoris rufomarginatus (underneath)


L. rufo
Photo: Robert Whyte

An experiment is underway to give some Leptocoris rufomarginatus access to Jagera pseudorhus fruit capsules and seed in a terrarium in an attempt to observe feeding. (See more on this below.)

Image: Leptocoris rufomarginatus (nymph)


Leptocoris rufomarginatus

This photograph by Mark Crocker was taken of a nymph sheltering on a Diospyros fasciculosa under a Jagera pseudorhus. About two weeks previously a savage storm ripped through this area accompanied by heavy hail. This may have stripped the Jagera of bugs many of which where not yet flying adults. They are likely to to have walked to the nearest safe place, the flying adults moving to the Jagera to feed but often returning to be with the juveniles as they developed.

Image: Leptocoris rufomarginatus (adult)


Leptocoris rufomarginatus

The blue pane of this bug's wing must have some evolutionary advantage, perhaps to warn potential predators of the unpleasant taste garnered by feeding on cyanide collecting seeds of the SAPINDACEAE.

Image: Leptocoris rufomarginatus feeding on a seed of Jagera psuedorhus


Leptocoris rufomarginatus
Photo: Robert Whyte

This photograph shows L. rufomarginatus feeding on seed of Jagera psuedorhus. The posture, beak deployment and general look of contentment are most consistent with feeding. The accompanying video (below) reveals more.

Image: Leptocoris rufomarginatus feeding on a seed of Jagera psuedorhus


Leptocoris rufomarginatus
Photo: Robert Whyte

This photograph is definitive proof of L. rufomarginatus feeding on seeds of Jagera psuedorhus. The beak is penetrating the seed casing.

The beak is a jointed tube (labium), with four long, narrow, flexible, chisel-tipped stylets within. They can be used as a seemingly unified structure, or sometimes the labium is partially folded back from the stylets.

The stylets do the penetration and excavation. The labium houses also provides a channel for the expulsion of digestive saliva into the seeds, and the piping of the liquefied material back into the body with a suction pump apparatus in the mouth region.

References


This movie shows the feeding bug on the seed. Note the small white mark on the seed when the bug removes its beak and moves off. This is digested seed matter.