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Aphididae : Aphidinae : Macrosiphini : Abstrusomyzus
 

 

Genus Abstrusomyzus

Abstrusomyzus aphids

On this page: Abstrusomyzus phloxae

Abstrusomyzus [Macrosiphini]

Abstrusomyzus are small to medium sized aphids, mostly dark, but with one common pale species. The apterous viviparae have small sparse spinules on the dorsum of the head capsule, often arranged in curving rows. The antennal tubercles are moderately to strongly produced. The frons is often produced slightly as a median tubercle bearing large ventral projections. The antennae are normally shorter than the body. In apterae antennal segment III is covered with imbrications, with rarely 1 or 2 secondary rhinaria. In the alate antennal segment III has secondary rhinaria scattered over most or all of its length, limited to one side, but normally less than 20 in number; there are a few on segment IV but none on segment V. The hairs on the head are short, blunt, and much shorter than the basal width of antennal segment III. The rostrum has segment II strongly ornamented with rows of spinules, and segment III has 2 pairs of hairs. The apical rostral segment (RIV+V) is about equal in length to the second hind tarsal segment (HTII). The pronotum has a pair of marginal tubercles that are sometimes bifid or trifid. The surface of the thoracic terga is reticulate and often pigmented. The first tarsal segments of fore, mid, and hind legs have 3,3,2 setae respectively. The abdomen has the tergum reticulate throughout, and is pigmented in most, but not all, species. The alate abdomen has dark marginal sclerites, and often dark cross bands on some segments; the cross bands are reticulate as on the tergum of apterous viviparae. Dorsal abdominal hairs are mostly very short. Abdominal segments II-VI often have marginal tubercles of various sizes. The siphunculi are cylindrical over most of their length, but slightly swollen toward the tip, imbricated throughout, and with a small flange. Tergite VIII has 4-7 hairs, normally 4. The cauda is moderately long, with 4-15 hairs. The body length of apterae is 0.83-1.94 mm, and of alatae 0.98-1.92 mm.

There are 4 Abstrusomyzus species, all previously placed in the genus Ovatus. One species (Abstrusomyzus phloxae - see below) is highly polyphagous, but the others appear to be monophagous. Abstrusomyzus leucocrini is found on sand lilies (Leucocrinum spp.), Abstrusomyzus reticulatus is found on wood sorrel (Oxalis spp.) and Abstrusomyzus valulilae on wild strawberry (Fragaria vesca). Abstrusomyzus species are, thus far, all restricted to North America.

 

Abstrusomyzus phloxae (Obscure dark-tipped aphid)

Adult apterae of Abstrusomyzus phloxae are pale apple-green with faint orange patches around their siphuncular bases. The head is ornamented with numerous spicules, and the antennal tubercles are moderately developed with prominent converging scabrous processes extending from the antennal bases. The dorsal abdomen is without dark markings, but does have hexagonal reticulation which is faint due to the pale, unsclerotized tergum (cf. Abstrusomyzus reticulatus, Abstrusomyzus valuliae & Abstrusomyzus leucocrini, which all have the dorsum of the abdomen dark pigmented, usually black). The siphunculi are mostly pale but with a dark tip (cf. Aphis asclepiadis, Aphis fabae, Aphis gossypii, Aphis plantaginis, Aphis frangulae, Aphis spiraecola & Protaphis middletonii, all of which have dark siphunculi). The siphunculi are slightly swollen subapically over about the distal quarter (cf. Aulacorthum solani, Myzus ornatus & Neomyzus circumflexus, which have the distal half of the siphunculi tapering or cylindrical, and Rhopalosiphoninus latysiphon and Rhopalosiphoninus staphyleae, which have the siphunculi markedly swollen). The body length of adult Abstrusomyzus phloxae apterae is 1.2-1.8 mm.

First image above copyright Andrew Jensen under a cc by-nc-sa licence
Second image above copyright Gregory Parks, AphID, Bugwood.org under a cc by-nc-sa licence.

The dorsal abdomen of the alate Abstrusomyzus phloxae (see second picture above) has dark lateral sclerites, with interrupted cross bands on some segments which often have hexagonal reticulation similar to the tergum of apterous vivipara.

Abstrusomyzus phloxae is a polyphagous species, having been recorded from several Asteraceae (Achillea, Agoseris, Centaurea) and from a number of unrelated genera including Apocynum, Capsella, Carex, Cerastium, Galium, Phacelia, Phlox, Plantago, Polygonum, Ranunculus, Stellaria, Trifolium, Viola. In the eastern USA Abstrusomyzus phloxae is most common on Plantago, and in the western USA it is common on Apocynum. Note that Abstrusomyzus on strawberries (Fragaria spp.) are more likely to be Abstrusomyzus valuliae and on Oxalis spp. are more likely to be Abstrusomyzus reticulatus (Jensen & Stoetzel, 1999). Usually Abstrusomyzus phloxae colonizes the basal or rosette leaves of low-growing plants where colonies are often ant-tented. On Apocynum it feeds on the undersides of leaves causing characteristic leaf tissue yellowing. Abstrusomyzus phloxae mainly reproduces parthenogenetically all year, but oviparae have been found in Nova Scotia. The species is widely distributed in North America.

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Acknowledgements

We have used the genus description of Jensen & Stoetzel (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).

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References

  • Blackman, R.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.

  • Jensen, A.S. & Stoetzel, M.B. (1999). An examination of the North American aphid species currently placed in Ovatus van der Goot (Hemiptera: Aphididae) with the description of a new genus. Proceedings of the Entomological Society of Washington 101(1), 39-56. Full text