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Aphidinae : Macrosiphini : Cedoaphis
 

 

Genus Cedoaphis

Cedoaphis aphids

On this page: Genus Cedoaphis incognita

Cedoaphis [Macrosiphini]

Cedoaphis is a North American genus erected by Oestlund (1922) for a species with secondary rhinaria in the apterae, a helmet-shaped cauda, and large rather flat marginal tubercles. Several authorities have expressed doubt about the validity of this genus. For example, Palmer (1952), commented that similar marginal tubercles are found in several species of widely separated genera, and classified the species as Aphis incognita. Blackman doubted that Cedoaphis incognita and Cedoaphis maxsoni (the only 2 species currently recognised) belong in the same genus. Andrew Jensen in AphidTrek accepted that those two species were probably not congeneric, but has suggested that the genus name Cedoaphis can validly be applied to what he believes are 2-4 species, possibly feeding on different species of Symphoricarpos, currently lumped under Cedoaphis incognita.

Pike et al. (2003) have detailed the currently accepted diagnostic characteristics. The antennal tubercles are weakly to moderately developed. The median frontal tubercle is equal to, but not exceeding, the antennal tubercles in height. Secondary rhinaria are numerous on antennal segments III-V. The terminal process is greater than 4 times the base of antennal segment VI. The hind tibia has pseudosensoria basally. Abdominal tergites I-VII have large shallow or flat round marginal tubercles. The siphunculi are cylindrical, and imbricated. The cauda is relatively short, and helmet-shaped.

 

Cedoaphis incognita (Green snowberry aphid)

Adult apterae of Cedoaphis incognita are yellowish green with a dusky brown head. Their appendages are pale with dusky tips. The siphunculi are yellowish but dusky apically, and the cauda, anal and genital plates are brown. Antennal segments III-V have numerous secondary rhinaria along most of their length, with 13-28 on segment III, 8-18 on segment IV, and 1-8 on segment V (cf. Aphthargelia symphoricarpi, which has antennal segments III-V without rhinaria or with only 1-3 rhinaria near base of III). There are light brown transverse mid-dorsal bands on tergites VI-VIII. Abdominal tergites I-VII have flat round marginal tubercles (cf. Amphicercidus pulverulens & Amphicercidus flocculosus, which either have no marginal tubercles present, or if present they are very small, papilliform and restricted to abdominal tergites II-V). The siphunculi are cylindrical, with the flange imbricated. The cauda is short and rounded or helmet-shaped, not longer than its basal width in dorsal view and bearing at least 20 long fine hairs.

Image above copyright Andrew Jensen, under a cc by-nc-sa licence.

Cedoaphis incognita alatae (see second picture above of an alate Cedoaphis sp.) have secondary rhinaria on the antennae distributed III 22-28, IV 15-18, V 10-14. There are dark lateral spots anterior to the siphunculi and dark bands on abdominal tergites VI, VII, and VIII. The antennae, siphunculi, cauda and legs are blackish.

The primary hosts of Cedoaphis incognita are several species of snowberry (Symphoricarpos). Andrew Jensen in Aphidtrek reported finding Cedoaphis fundatrices (see third picture above) in characteristic leaf curl galls at the end of snowberry branches, first noted by Oestlund (1887) (as Aphis symphoricarpi) on the leaves of Symphoricarpa vulgaris. Jensen found there were two life cycle strategies for Cedoaphis incognita. Most spring leaf curl galls are abandoned by alate viviparae, which migrate to the crowns of Indian paintbrush (Castilleja spp.). Then in autumn males and female sexuparae migrate back to Symphoricarpos, where oviparae are produced. Alternatively some leaf galls remain occupied all summer, with sexuales produced in autumn. Whether these two strategies represent two different species is as yet unknown. We also note that finding fundatrices in leaf curls was contrary to the view of Gillette and Palmer (1932) who suggested that fundatrices lived on the roots in spring. Cedoaphis incognita is vigorously ant-attended on both Symphoricarpos and Castilleja. Cedoaphis incognita is widely distributed in the USA.

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Acknowledgements

We are grateful to Andrew Jensen for making his images of Cedoaphis incognita available for use under creative commons licences.

Identification was made by Andrew Jensen by microscopic examination of preserved specimens. We have used the keys and species accounts of Oestlund (1887) (as Aphis symphoricarpi), Gillette and Palmer (1932) & Palmer (1952) (both as Aphis incognita), and the genus account of Pike et al. (2003), 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 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).

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References

  • Oestlund, O.W. (1887). Synopsis of the Aphididae of Minnesota. Bulletin No. 4. Full text

  • Palmer, M.A. (1952). Aphids of the Rocky Mountain Region: including primarily Colorado and Utah, but also bordering area composed of southern Wyoming, southeastern Idaho and northern New Mexico. Full text

  • Pike, K. et al. (2003). Aphids of Western North America North of Mexico with Keys to Subfamilies and Genera for Female Alatae Washington State University, Pullman (p. 89)