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Aphidinae : Macrosiphini : Macrosiphum rhamni
 

 

Macrosiphum rhamni

Buckthorn-fern aphid

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

Identification & Distribution

Adult apterous viviparae of Macrosiphum rhamni are yellow green. The oviparae (see picture below), additionally have a large round patch of reddish internal pigment in the centre of the dorsum (this may also apply to other morphs, but see note below). The antennae are pale with the joints between segments III-IV and IV-V (& segment VI in the ovipara) contrastingly black (cf. Macrosiphum clydesmithi & Macrosiphum osmaroniae, which have those joints dusky). The antennal tubercles are well-developed, and divergent. The antennae are longer than the body, with the terminal process more than 6 times as long as the base of antennal segment VI. Antennal segment III has (0-)1-2 secondary rhinaria near the base (cf. Macrosiphum pteridis and Macrosiphum ptericolens, which have more than 3-35 rhinaria on that segment). The apical rostral segment (RIV+V) is 1.3-2.1 times as long as the second hind tarsal segment (HTII), and has 5-8 accessory hairs. RIV+V is 0.15-0.17 mm in length (cf. Macrosiphum dryopteridis, which has RIV+V < 0.14 mm.). The abdominal dorsum is entirely sclerotic, pale and generally smooth. The siphunculi and cauda are pale. The siphunculi are 3-4 times as long as the short cauda, with only 1-3 rows of hexagonal reticulations at its apex. The rather short bluntly triangular cauda has 6-9 hairs. The body length of Macrosiphum rhamni apterae on buckthorn is 1.8-2.4 mm, on fern they are 1.8-2.6 mm.

Note: The literature is rather contradictory on which morphs display a reddish spot on their dorsum. Blackman, quoting Essig (1917), reports it as present on apterous viviparae on Rhamnus in spring. Wilson (1912) reported the presence of "an orange spot in the centre of the body just back of the thorax" on some emigrant alatae on the primary host in June. Jensen & Holman (2000) report the red spot is present on summer and autumn specimens on Rhamnus, but in Aphidtrek (undated) Jensen states explicitly that "the red internal pigment is typical for oviparae and no other morph". The red spot is certainly not present on apterae on the secondary host - at least we have found no record of such.

Image above copyright Andrew Jensen, under a creative common licence.

The alate Macrosiphum rhamni (not pictured) is lemon-yellow, with orange head and thorax; the antennae have segments I, II and base of III pale, and the remainder dusky to black. Antennal segment III bears about 25 nearly circular secondary rhinaria of variable sizes and irregularly placed. The basal halves of the siphunculi are pale, the distal halves dusky to black. The siphunculi in alatae have reticulations covering the distal 0.5.

Macrosiphum rhamni is dioecious, host alternating from the primary host buckthorn, specifically California coffeeberry (Rhamnus californica) and cascara (Rhamnus purshiana), to the secondary hosts, ferns (Pteridium). In western Oregon the eggs hatch from mid-February to March, with adult fundatrices present from mid-March to late April. There is usually a second generation of apterous viviparae, followed by a third generation comprised of emigrant alatae which migrate to Pteridium. In some areas a small number remain on buckthorn all summer. Gynoparae and males return to Rhamnus in autumn, and oviparae can be found abundantly from mid-October to late November. Jensen & Holman (2000) note that males and alate viviparae often drop readily when disturbed, but apterae less so. They also note that they are frequently ant-attended, as is the case for another member of the Macrosiphini, Macrosiphum weberi, in Europe.

 

Other aphids on the same host

Primary hosts

Macrosiphum rhamni has been reported on 2 buckthorn species (Rhamnus californica, Rhamnus purshiana).

Secondary hosts

Macrosiphum rhamni has been reported on one Pteridium species (Pteridium aquilinum).

Acknowledgements

We are grateful to Andrew Jensen for making his images of Macrosiphum rhamni available for use under a creative commons licence.

We have used the species accounts given by Clarke (1903) (as Nectarophora rhamni), Wilson (1912) (as Myzus rhamni), Essig (1917) and Jensen & Holman (2000), 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).

Useful weblinks

References

  • Clarke, W.D. (1903). A list of California Aphididae. The Canadian Entomologist 35(9), 247-254 (p.252). Abstract

  • Essig, E.O. (1917). Aphididae of California: New species of Aphididae and notes from various parts of the state, but chiefly from the campus of the University of California, Berkeley, California. University of California Publications Technical Bulletins College of Agriculture, Agricultural Experiment Station, Entomology 1(7), 302-346. (p. 314)

  • Jensen, A.S. & Holman, J. (2000). Macrosiphum on ferns: taxonomy, biology and evolution, including the description of three new species (Hemiptera: Aphididae). Systematic Entomology 25, 339-372. Abstract

  • Wilson, H.F. (1912). Aphid notes from Oregon. The Canadian Entomologist 44(5), 153-159 (p. 153). Full text