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Aphididae : Calaphidinae : Panaphidini : Neosymydobius


Genus Neosymydobius

American oak-twig aphids

On this page: Neosymydobius albasiphus paucisetosus

Neosymydobius [Panaphidini]

Neosymydobius have the median frontal and antennal tubercles undeveloped. The secondary rhinaria on antennal segment III are round, and distributed on half or more of the segment. The forewing veins are not fuscous bordered, or only faintly so. The abdomen has 0-5 marginal tubercles. The siphunculi are short and truncate. The cauda is rounded to weakly knobbed, and the anal plate is bilobed.

There are about 14 species of Neosymydobius monoecious holocyclic on oak (Quercus). They resemble aphids of the genus Symydobius, but are not closely related to them. Neosymydobius is in tribe Panaphidini, whereas Symydobius is in tribe Calaphidini. Their similar appearance appears to result from convergent evolution given their feeding site (on bark of terminal twigs) and ant attendance. They are all found in North America.


Neosymydobius albasiphus (White-cornicled oak aphid) Eastern USA, Canada

Adult apterae of Neosymydobius albasiphus (see pictures below) are shining black or brown with a pale spinal stripe. There is conspicuous white wax around the siphunculi and on the cauda. Their antennal tubercles are poorly developed. The antennae are pale with black annuli at the apices of the segments (cf. Neosymydobius neomexicanus in New Mexico, USA, which has antennal segments III-VI almost entirely dark). The terminal process is more than 0.5 times as long as the base of antennal segment VI (cf. most other Neosymydobius spp., which have the terminal process less than 0.4 times the base of that segment). The hairs on antennal segment III are slender, with the longest about 0.67 times the basal diameter of that segment. The apical rostral segment (RIV+V) has 4-6 accessory hairs. Each abdominal tergite has a transverse, pigmented sclerotic bar that may be broken in the middle on some segments (cf. most other Neosymydobius spp., which have no transverse abdominal bars, but only small sclerites). Each abdominal segment has one or more transverse rows of mostly long fine hairs dorsally and a cluster laterally. Lateral abdominal sclerites are also present on each segment. The fore- and mid-legs are very pale fuscous and the hind legs are dark brown apart from the tibial apices. The cauda is weakly knobbed, and the anal plate is deeply indented. The body length of adult Neosymydobius albasiphus apterae is 1.4-1.9 mm.

Images above copyright Ashley Bradford under a Creative Commons License.

Alatae of Neosymydobius albasiphus (not pictured) are coloured similar to the apterae. The wings have dark costal veins, but other veins are not bordered.

Neosymydobius albasiphus feeds on various Nearctic oak species including white oak (Quercus alba), bur oak (Quercus macrocarpa), swamp chestnut oak (Quercus michauxii), swamp Spanish oak (Quercus palustris) and post oak (Quercus stellata). Davis 1914 provided some interesting observations on its biology in Indiana, USA. In all cases the aphid was found on leaves near the leaf petiole, usually on the under leaf surface, and invariably attended by the ant, Crematogaster lineolata. In Virginia, USA, they had also been found tented over with mud on the upper side of the leaf. Oviparae and alate males occurred in September-October. Neosymydobius albasiphus is found in eastern USA and Canada.



Neosymydobius paucisetosus (Red-headed brown oak aphid) California

In life, adult apterae of Neosymydobius paucisetosus have a red-brown head. Their dorsum colour varies from dark brown with some pale patches to very pale brown with slightly darker brown patches (see two pictures below). Antennal segments I and II are brown, segments III-V are pale fuscous with black apices, and segment VI black. The base of antennal segment VI has only 1-5 (rarely 7) hairs (cf. Neosymydobius agrifoliae, which has 10-20 hairs on the base of antennal segment VI). The pronotum has anterior and posterior sclerites separated. There is very little (or no) spinal or pleural sclerotization on the mesonotum, metanotum, and abdominal tergites I-VI, but they may or may not have small sclerites or scleroites present (cf. Neosymydobius albasiphus, which has a large tranverse sclerotic band on each of tergites I-V). The abdominal sclerites may be larger on the posterior abdomen, and on tergites VI-VIII they form transverse sclerotic bands. In addition there are weakly sclerotized, roundish brown marginal sclerites on each abdominal segment. The femoral hairs are blunt and rather short, up to 0.025 mm long (cf. Neosymydobius rumorosensis, which has hairs on the femora pointed with wavy apices, the longest up to 0.045mm) The hind tibiae are mostly pale in the middle (cf. Neosymydobius agrifoliae, which has most of the hind tibiae uniformly black). The siphunculi are sclerotic, with a pale apical flange. The cauda is rounded, tongue-shaped, with a posterior sclerotic margin bearing 20-30 hairs. The body length of adult Neosymydobius paucisetosus apterae is 1.7-2.5 mm.

Images above copyright Jesse Rorabaugh under a public domain (CCO) licence.

Alatae (not pictured) are coloured much the same as apterae. The wings have pigmentation along the costal margin and sometimes diffuse brown mottling on the pterostigma. Other veins have diffuse pale brown bordering, particularly beside vein Cul b. Antennal segment III bears 3-8 secondary rhinaria.

Neosymydobius paucisetosus feeds on various western American oak species, including California live oak (Quercus agrifolia), canyon live oak (Quercus chrysolepis, blue oak (Quercus douglasii), coastal sage scrub oak (Quercus dumosa), valley oak (Quercus lobata) and interior live oak (Quercus wislizeni). It is closely related to Neosymydobius agrifoliae (Quednau, 1994). Neosymydobius paucisetosus is monoecious holocyclic, with sexuales having been found in September-October. So far Neosymydobius paucisetosus has only been recorded in California, USA.



We have used the genus account given by Pike et al. (2003),& the species accounts of Richards (1965), Quednau (1994), Quednau (1999), together with information from 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


  • Pike, K.S. et al. (2003). Aphids of Western North America North of Mexico with Keys to Subfamilies and Genera for Female Alatae. WSU Extension Bulletin Office 282 pp.

  • Quednau (1994). Taxonomic notes on the genus Neosymydobius Baker with descriptions of five new species (Homoptera: Aphididae). The Canadian Entomologist 126, 1443- 1458. Abstract

  • Quednau, F.W. (1999). Atlas of the Drepanosiphine aphids of the World. Part I: Panaphidini - Myzocallidinae. Contrib. Am. ent. Inst 31, 1-281.

  • Richards, W.R. (1965). The Callaphidini of Canada (Homoptera: Aphididae). Memoirs of the Entomological Society of Canada 44, 1-149. Abstract