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Hormaphidinae : Cerataphidini : Pseudoregma sundanica
 

 

Pseudoregma sundanica

Snowbell-ginger soldier aphid

On this page: Identification Biology & Distribution Other aphids on the same host

Identification & Distribution

Pseudoregma sundanica fundatrices induce complex galls up to 6.8 cm in diameter (see pictures below) from developing flower buds on old twigs of Styrax paralleloneura, their primary host. Each gall comprises up to seven sub-galls joined to a central calyx - the fundatrix's gall. This calyx-like structure, which is more swollen than normal floral calyxes, remains at the base of each gall. Each subgall is rather wide and swollen, but sometimes flattened, and has a rather long slit (up to 26mm) at the apex which enlarges as the gall develops. The outer surface of subgalls is densely covered with velvet-like hairs that apparently functions to catch wax from the body surface of the aphids (presumably their soldiers). The wax functions as a water repellent, and may deter unwlcome visitors. The wax-covered gall looks white, except for green internal projections which can be seen through the slit. These projections provide mechanical support for the gall structure and increase feeding area for the aphids. The second image below shows a gall damaged during its development.

Images above by permission, copyright Aoki & Kurosu, all rights reserved.

  • Some immatures in the gall develop to soldier forms. Their development is halted at the second instar, rendering them sterile. Second instar soldiers of Pseudoregma sundanica have the tergum sclerotized with long hairs, and greatly thickened forelegs with large, strongly curved claws. Their siphunculi are distinctly protruding. Some soldiers remain inside the gall, but many may move to outside the gall, mostly aggregated around gall bases (see picture below). Their dark body colour is visible owing to wax loss.
  • The remaining nymphs develop normally inside their gall - to apterous viviparae during gall development (which do not seem to have been described) or to emigrant alatae - which migrate to their secondary host, one of the ginger family. (No gall-derived sexuparae or sexuales of Pseudoregma sundanica have been recorded.) Normal second instars have the tergum membranous with shorter hairs, their forelegs are only slightly thickened, their siphunculi are ring-like and only slightly protruding.

Image above by permission, copyright Aoki & Kurosu, all rights reserved.

The alate emigrant from the gall (not pictured) has a broadly rounded head without frontal horns, and with about 40-47 rather short dorsal hairs, which are absent on the posterior marginal area. The front ocellus is on an eminent protuberance. The antennae are 5-segmented with a short terminal process. Secondary rhinaria are narrow, often nearly completely encircling the segment. Antennal segments III, IV and V have respectively 18-23, 8-11 and 6-9 secondary rhinaria. The rostrum extends beyond the fore coxae, with the apical rostral segment conical, and no secondary hairs. The abdomen is weakly sclerotized and dusky on tergites VII & VIII. The siphunculi are surrounded by 4-6 hairs. The cauda is broadly rounded on the hind margin, not constricted at the base, much wider than long, and with 13-18 long hairs. The anal plate is divided, its lobes are as wide as the cauda. The body length is 1.6-2.0 mm.

Pseudoregma sundanica apterae on the secondary hosts are blackish brown or black, with the last abdominal segments paler. Their antennae and legs are pale brown with the apical segments darker. Tufts of white wax may be present, or there may be a continuous layer of wax ventral to the marginal wax glands, and sometimes a pleural layer of wax. The head is fused with the pronotum, and bears a pair of forwardly-directed horns with rounded tips between the antennal bases. Dorsal hairs on the head are 28-45 μm long, and those on abdominal tergite VIII are 37-59 μm long (cf. Pseudoregma nicolaiae, also on ginger, which has longer dorsal hairs: on the head 69-78 μm long, and on abdominal tergite VIII 80-92 μm long). Wax gland plates may or may not be present; if present, then they tend to be in groups, for example on the pronotum in groups of 0-5, and on abdominal tergite II in groups of 0-6 (cf. Pseudoregma nicolaiae which has well developed wax glands, on the pronotum in groups of 7-17, and on abdominal tergite II in groups of 7-12). The abdominal tergites are mainly brown, sclerotic, and ornamented with numerous pustules. The siphunculi are simple pores.

The first instar soldier form on the secondary host has 4-segmented antennae. The frons bears two horns. The fore-legs are darker brown, more sclerotic and sturdy than the other legs. There are star-shaped oval wax glands on all sclerotic parts of the body. There are marginal abdominal sclerites dorsally each with one hair. Siphunculi are absent or rudimentary and the cauda has two hairs.

 

Biology & Distribution

Pseudoregma sundanica gall generations on their primary host, Styrax paralleloneura, are only known from northern Sumatra. They are not generally ant-attended on the primary host, although sometimes ants may collect honeydew directly from openings of a gall. Defense of the colony is mainly carried out by the second-instar soldiers. As well as protecting the aphids, soldier aphids also carry out cleaning duties for the colonies.

Secondary host generations are much more widely distributed in east and south-east Asia. They occur on various plants of the ginger family (Zingiberaceae) (Alpinia, Amomum, Costus, Etlingera, Zingiber). The aphids live densely together on petiole bases, main leaf veins, leaf sheaths, or stems. Most colonies are attended by ants which protect the aphids from predators and often tent the aphid colonies with pieces of leaves and flowers. But as an additional defence, larger colonies of Pseudoregma sundanica (> 200 individuals) on the secondary host have a sterile first instar soldier caste comprising 5-10% of the total aphid aggregation (Schütze & Maschwitz, 1991). Aphid predators not being attacked by the ants (e.g. larvae of aphidophagous Miletinae Lycaenids) are attacked by these soldiers. It has been shown experimentally that if ants are excluded from colonies of Pseudoregma sundanica, more soldiers are produced, and there is more leg waving (Shingelton & Foster, 2000). The aphids wave their hind legs around when disturbed in the same way as Lachnus roboris aphids elevate their posterior pair of legs when disturbed. Leg-waving has been termed 'unspecific defensive behaviour', although it is unclear how this behaviour protects the aphid (Aoki & Kurosu, 2010). Pseudoregma sundanica is found in Java, Malaya, Sumatra, and Philippines, and has been introduced to Australia.

 

Other aphids on the same host

Primary host

Pseudoregma sundanica has been recorded on 1 snowbell species (Styrax paralleloneurus).

Blackman & Eastop list 3 species of aphid as feeding on Styrax paralleloneurus worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists none occurring in Britain (Show British list).

Secondary hosts

Pseudoregma sundanica has been recorded on 1 ginger species (Zingiber officinale).

Blackman & Eastop list 3 species of aphid as feeding on Zingiber-officinale worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).

Acknowledgements

We are especially grateful to Utako Kurosu & Shigeyuki Aoki for images from their review paper (Aoki & Kurosu, 2010) for this page.

We have used the keys and species accounts of Van der Goot (1918) (as Oregma sundanica), Noordam (1991), Kurosu & Aoki (2001), and Aoki & Kurosu (2010) together with those of Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References

  • Aoki, S. & Kuruso, U. (2010). A review of the biology of Cerataphidini (Hemiptera, Aphididae, Hormaphidinae), focusing mainly on their life cycles, gall formation, and soldiers. Psyche, Article ID 380351. Full text.

  • Kurosu, U. & Aoki, S. (2001). Discovery of the gall generation of the Ginger Aphid Pseudoregma sundanica (Homoptera). Entomological Science, 4(2): 209-215. Full text

  • Noordam, D. (1991). Hormaphidinae from Java (Homoptera: Aphididae). Zool. Verh. Leiden 270, 1-525. Full text

  • Schütze, M. & Maschwitz, U. (1991). Enemy recognition and defence within trophobiotic associations with ants by the soldier caste of Pseudoregma sundanica (Homoptera: Aphidoidea). Entomol. Gener. 16(1): 001-012. Abstract

  • Shingleton, A.W. & Foster, W.A. (2000). Ant tending influences soldier production in a social aphid. Proceedings of the Royal Society of London B 267, 1863-1868. Full text

  • Van der Goot, P. (1918). Notes on Oriental Aphididae. Tijdschrift voor Entomologie 61, 112-127. Full text