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Aphidinae : Macrosiphini : Macrosiphum osmaroniae


Macrosiphum osmaroniae

Osoberry-fern aphid

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

Identification & Distribution

Adult apterae of Macrosiphum osmaroniae (see first picture below of a fundatrix) are pale to mid-green in colour, with a yellowish-orange head and cauda. Its antennal tubercles are large and distinct. The antennae are longer than the body, and have 14-36 secondary rhinaria, mostly on the basal half of segment III. The joints between antennal segments III & IV and IV & V are dusky (cf. Macrosiphum rhamni, which has those joints contrastingly black). The apical rostral segment (RIV+V) is 0.83-1.27 times as long as the second hind tarsal segment (HTII), and bears 6-8 hairs (cf. Macrosiphum ptericolens & Macrosiphum pteridis on Pteridium, which both have RIV+V 1.2-1.55 times HTII; and Macrosiphum occidentale on Oemleria, which has RIV+V 0.7-0.8 times HTII). There are spinal tubercles sometimes present on the head and tergites VII & VIII. The abdominal dorsum is entirely sclerotized, but is pale and sometimes wrinkled. The siphunculi are about 2.7 times the length of the elongate cauda, and have about 6 rows of distinct reticulations (cf. Macrosiphum clydesmithi on Pteridium, which has 0-3 rows of often rather indistinct subapical reticulation). The body length of adult Macrosiphum osmaroniae apterae is 2.7-3.5 mm.

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

The alate Macrosiphum osmaroniae (see second picture above) is light green with an orange head and thorax. The antennae bear 23-53 secondary rhinaria on segment III.

Macrosiphum osmaroniae host alternates from its primary host, osoberry (Oemleria cerasiformis) to its secondary host bracken fern (Pteridium aquilinum). Eggs on osoberry hatch at budbreak in spring to give the fundatrices. These feed among the leaves of the unfurling bud. Fundatrices mature in March-April, and produce a second generation of apterous viviparae which in turn produce the alate migrants. These move to bracken, where small populations develop. In early autumn small numbers of gynoparae return to the primary host, followed later by males which mate with the newly developed oviparae. Jensen & Holman (2000) noted that in autumn Macrosiphum osmaroniae are usually found on osoberry growing in deep shade and near streams, most likely because they retain their leaves longer than plants in exposed situations. The species is currently known from British Columbia in Canada, and Washington and Oregon in USA, and is thought to be also present in California.


Other aphids on the same host

Primary host

Macrosiphum osmaroniae has been reported on one Oemleria species (Oemleria cerasiformis).

Secondary host

Macrosiphum osmaroniae has been reported on one Pteridium species, Pteridium aquilinum.


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

We have used the species accounts given by Wilson (1912) (as Illinoia osmaroniae) 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


  • 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