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Hormaphidinae : Cerataphidini : Pseudoregma carolinensis
 

 

Pseudoregma carolinensis

Southern bamboo woolly aphid

On this page: Identification: Taxonomy Primary host Secondary host Summary & distribution Other aphids on the same host

Identification

Taxonomy

Pseudoregma carolinensis (=Oregma bambusae var. carolinensis Takahashi, 1941) was only recognised as genetically and geographically distinct from Pseudoregma bambucicola following the work of Fukatsu et al. (2001). On their secondary host (bamboo species) the two species are almost indistinguishable morphologically, but their primary host, gall structure and distribution are very different (Aoki et al., 2002). It is uncertain whether the aphids that have been recorded on bamboo as Pseudoregma bambucicola from India, Sri Lanka, and Fiji (Blackman & Eastop, 1994) are Pseudoregma bambucicola, Pseudoregma carolinensis or a third species, but Fukatsu et al. (2001) suggest that they are Pseudoregma carolinensis. For more on this see taxonomy under Pseudoregma bambucicola.

Primary host

Fundatrices of Pseudoregma carolinensis induce "fresh green"-coloured galls on their primary host, Styrax benzoides. The mature gall comprises a cluster of petiolate rolled sub-galls formed from a flower bud (see picture below) (cf. Pseudoregma bambucicola, which forms galls on Styrax suberifolius, that are larger and flatter, with beak-like apical extensions; and cf. subgalls of Pseudoregma sundanica on Styrax paralleloneura, which are velvety white with green internal projections). The Pseudoregma carolinensis gall is one of the smallest multiple-cavity galls of ceraphidines, with 2-10 subgalls, each subgall being 4-6.9 mm wide and 12-24 mm long (excluding the apical hairlike projection). The subgall outer surface is almost smooth, with a short hairlike projection at the end. Towards the apex there is long slit or suture with several small osteoles (cf. Pseudoregma bambucicola, which has no longitudinal suture). At the base of each subgall cluster there is a fringe of several, shorter, needle like projections. Each gall contains 50-1500 aphids, of which 21-66% are soldiers (described below). Gall production probably varies according to the local rainy season, but their inhabited duration is unlikely to exceed a year.

Image above copyright Aoki & Kurosu (2010) under a creative commons licence.

Whilst Pseudoregma carolinensis galls and winged emigrants are readily distinguishable from those of Pseudoregma bambucicola, Pseudoregma koshunensis and Pseudoregma sundanica (which also form galls on trees in series Benzoin of the Styrax genus) - their gall-dwelling aphids are "very similar" (morphlogically, at least).

The colour of live Pseudoregma carolinensis gall-dwelling apterae is unknown, but they are presumably waxy. The adult aptera (previously undescribed, but taken from the clarified mount below) has 5-segmented antennae which are 0.30 times the body length. The terminal process of the last antennal segment is 0.35 times its base, and 0.016 times as long as the body (cf. Pseudoregma bambucicola, whose antennae have 4 segments, are 0.18 times the body length, with a terminal process that is 0.44 times the base, and 0.017 times the body length). The eyes of apterae and young nymphs have only 3 ommatidia. There are a pair of forward-pointing horn-like processes on the front of the head, but much-reduced compared to those of the secondary host apterae. The apical rostral segment (RIV+V) is 0.09 mm long, and 0.89 times the second hind tarsal segment (HTII) (cf. Pseudoregma bambucicola, where RIV+V is 0.067 mm, and 0.75 times HTII). Abdominal segments appear to be un-sclerotized, aside from the areas around their siphuncular pores, which are distinctly sclerotised (cf. Pseudoregma bambucicola, where the latter are not distinctly sclerotised). The adult aptera body length is 1.20 mm (cf. 1.37 mm for Pseudoregma bambucicola). Note, in both cases n=1.

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

First-instar nymphs have only 1 pair of long setae on each first tarsal segment, 4-segmented antennae and unsclerotized siphuncular pores. Second and later instar nymphs have 1-2 spine-like setae and a pair of long setae on the first tarsal segment of mid- and forelegs, 5-segmented antennae, and ring-like siphunculi. There are two types of second-instar larvae:

  1. Normal second instar nymphs. These have a frons with 2 thickened spine-like setae up to 0.012-0.016 mm long, 0.002 mm wide at base, in a socket 0.006 mm wide at base. The foreleg is slightly thickened; femoral trochanter 0.18-0.20 mm long, 0.044-0.054 mm wide, with normal or slightly larger claws than the mid & hind legs. The tergum is membranous. Their body length is 0.83-0.97 mm. These develop to apterae or emigrant alatae. (Due to limited sample-size, sexuparae from the primary host are thus far unknown).

  2. Pseudoscorpion-like 'soldier' nymphs. These do not progress beyond the second instar, and are hence sterile. Soldier nymphs have a frons with slightly larger setae, 0.018-0.022 mm long, 0.004 mm at base, their sockets are 0.008-0.010 mm at base. The foreleg is greatly thickened; femoral trochanter 0.21-0.26 mm long, 0.050-0.068 mm wide, with large and strongly curved claws. The tergites are strongly sclerotized. Their body length is 0.71-0.85 mm long. These soldiers actively remove waste from the gall, and attack intruders with their stylets. Ants gleaning honeydew droplets at the gall are not attacked - but neither are nitulid beetle larvae (Carpophylus, a specialized predator) within it.

Emigrant alatae from the gall are described by Aoki et al (2002). These have 5-segmented antennae, with segment III about as long (0.91-1.10) as segments IV and V together. The terminal process is short, with 5 apical hairs. The secondary rhinaria are narrow, often completely encircling the segment; segment III has 16-29 secondary rhinaria, segment IV has 7-9, and segment V has 6-9. The apical rostral segment is conical and lacks secondary hairs. The fore-tibiae are nearly as thick as the antennae. The abdomen is weakly but extensively sclerotized on tergites VII and VIII, partially sclerotized on tergite VI, and distinctly sclerotized around the siphunculi, which are surrounded by 3-7 hairs (cf. Pseudoregma bambucicola, Pseudoregma sundanica and Pseudoregma koshunensis which lack sclerotization around the siphunculi). The cauda is broadly rounded on the hind margin, not constricted at the base and bears 16-20 long hairs. The anal plate is divided (bi-lobed), with 12-17 long hairs. The body length of alate viviparae is 1.33-1.82 mm.

Secondary host

Colonies on bamboo are notable for the presence of specialized soldier forms - a feature peculiar to Pseudoregma and some Ceratovacuna species. Forms on the secondary host are distinct from those on the primary host in having a larger pair of forward-pointing 'horns' (albeit less so for alates).

Adult apterae of Pseudoregma carolinensis on bamboo were described by Noordam (1991) (as Pseudoregma bambucicola), but they were probably Pseudoregma carolinensis. These are dark olive green to grey. In young colonies they may have three longitudinal rows of white wax tufts, but in older colonies those are less developed, and adults instead have a thick cushion of wax posterior to the siphunculi with white wax dusted elsewhere. Their antennae are dark brown, 4- or 5-segmented in apterae, in alatae always 5-segmented, 0.15-0.19 times the body length, and sparsely imbricated; the terminal process is at most 0.50 times the base of last antennal segment, and 0.12-0.15 times as long as the body. The apical rostral segment (RIV+V) tapers abruptly at the tip and is less than 0.12 mm long, at most 0.75 times the second hind tarsal segment (HTII). Abdominal segments I-VII have pale brown marginal sclerites, and there is a transverse elongated brown plate on tergite VIII. Sclerotic areas of dorsum, especially the head and pronotum, are evenly covered with small rounded and irregularly shaped pustules (star-shaped wax glands). The apterae are often without spinal wax glands. Abdominal tergites I-V may have 1-4 wax pore plates in paired spinal groups; there may also be 1-2 centrally on tergite VII and 1-4 centrally on tergite VIII. The siphunculi are pore-like and slightly elevated above the base. The cauda is rounded with 14-20 hairs.

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

There are two types of first instar larvae on the secondary host, normal & soldiers, both of which which differ from those of the primary host but resemble those of Pseudoregma bambucicola.

  1. Normal first instar nymphs are green, with a soft cuticle and thin forelegs. (Those deposited by alates are all normal, have sclerites and wax plates on their abdominal tergites.)

  2. Sterile soldiers are larger, have a sclerotized cuticle and a pair of sharp frontal horns and greatly enlarged forelegs.

Colonies can be distinguished to a limited extent from those of Pseudoregma bambucicola by the number of setae on the 8th abdominal tergite of their first instar nymphs. Fukatsu et al. (2001) found nearly all normal and soldier nymphs of Pseudoregma carolinensis have 2 setae (rarely 3), whereas 85% of normal Pseudoregma bambucicola nymphs had 4 setae (range 2-5) and 57% of soldiers had 4 setae (range 4-7).

The image below shows an ant-attended Pseudoregma carolinensis colony on a bamboo shoot, with many pseudoscorpion-like soldier nymphs.

Image above copyright Aoki & Kurosu (2010) under a creative commons licence.

Summary & distribution

In August Pseudoregma carolinensis host alternate from their galls on Styrax benzoides to their secondary hosts bamboo, especially Bambusa and Dendrocalamus species. Where the primary host is available, alate sexuparae (containing hornless dimorphic embryos) return to it in November-December where they produce sexuales - tiny, apterous males and females with a short rostrum. After mating, oviparae lay a single egg. Some populations are anholocyclic and continue with parthenogenetic reproduction on bamboos all year. Secondary migrants also occur on bamboos - these viviparous alatae disperse between bamboo plants (such secondary migrants are not known from Pseudoregma bambucicola). Pseudoregma carolinensis has a more southerly distribution than Pseudoregma bambucicola, being found in Thailand, Malay Peninsula, Java, Papua (Irian Jaya) and Micronesia.

 

Other aphids on the same host

Primary host

The only recorded primary host of Pseudoregma carolinensis is Styrax benzoides

Secondary hosts

Acknowledgements

We especially thank Shigeyuki Aoki (Professor Emeritus, Rissho University) and Utako Kurosu for sending us many of the images used on this page - and Aoki for his most helpful comments. We are also grateful to Sunil Joshi & J. Poorani for permitting us to use their images from Aphids of Karnataka.

We have used the keys and species accounts of Noordam (1991) Aoki et al. (2002) 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. et al. (2002). Discovery of the gall generation of the tropical bamboo aphid Pseudoregma carolinensis (Hemiptera) from northern Thailand. Entomological Science. 5(1):55-61.

  • Aoki, S. & Kurosu, U. (2010). A review of the biology of Cerataphidini (Hemiptera, Aphididae, Hormaphidinae), focusing mainly on their life cycles, gall formation, and soldiers. Psyche 2010, Article ID 380381, 34 pp. Full text

  • Fukatsu, T. et al. (2001). Genetically distinct populations in an Asian soldier-producing aphid, Pseudoregma bambucicola (Homoptera: Aphididae) identified by DNA fingerprinting and molecular phylogenetic analysis. Mol. Phyl. Evol. 18, 423-433. Behavioural Processes 40(1), 75-83. Abstract

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