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Aphidinae : Macrosiphini : Macrosiphum violae
 

 

Macrosiphum violae

Pioneer violet aphid

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

Identification & Distribution

Adult apterae of Macrosiphum violae (see first picture below) are very pale green, with pale brown eyes. The antennae have segments I-IV mainly pale, but the apex of V and all of VI are light brown. Antennal segment III bears 0-3 secondary rhinaria basally, with its longest hair 0.47-0.77 times as long as basal width of that segment. The ventral surface of the head has a broad band of spinules extending from the antennal tubercles to the posterior margin of head, with distinct patches of spinules on each side posteriorly (cf. Macrosiphum euphorbiae, which has no spinules on the ventral side of the head). The antennal tubercles are large and diverging. The rostrum reaches almost to the metacoxae, with the apical rostral segment (RIV+V) 0.94-1.26 times als long as the second hind tarsal segment (HTII) (cf. Macrosiphum euphorbiae, which has RIV+V 0.8-1.0 times HTII). The prothorax often has low marginal tubercles. The abdominal tergum is uniformly moderately sclerotic, and often lightly wrinkled. Some of abdominal tergites II-V usually have very small, low marginal tubercles. Tergites VII and VIII often have one or more low, indistinct spinal tubercles. The siphunculi are about 1.9 times the caudal length, 0.87-1.33 times antennal segment III, with 5-10 rows of reticulations. The cauda has 7-12 hairs. The body length of adult Macrosiphum violae apterae is 2.2-3.3 mm.

First image above copyright Andrew Jensen, second image copyright Walter Siegmund;
both under a creative common licence.

The alate vivipara of Macrosiphum violae has dark brown sclerotized plates on the thorax. The abdomen is green with large marginal sclerites on segments I-V, and large pleural intersegmental muscle attachment plates on segments I-VI. The postsiphuncular sclerites, and genital plate are light brown to dusky. The siphunculi are entirely brown, except the extreme base, which is distinctly lighter brown. Antennal segment III has 7-11 secondary rhinaria, which are restricted to the basal half.

Macrosiphum violae is monoecious on pioneer violet (Viola glabella, see second picture above). Jensen (2000) reports that attempts to transfer live aphids to two other violet species (Vancouveria hexandra and Viola sempervirella) were both unsuccessful. Jensen (2000) also describes the life cycle. The species is holocyclic. The overwintering eggs hatch as the leaves are unfolding in March, and fundatrices mature by mid-April. Aphid numbers reach their peak during flowering in late-emerging plants and fruiting in earlier-emerging plants. Apterae reproduce slowly throughout the summer, rarely producing alatae. Oviparae and alate males are produced in September and October in September-October. Macrosiphum violae is so far only known from north-western USA.

 

Other aphids on the same host

Blackman & Eastop list 2 species of aphid as feeding on pioneer violet (Viola glabella) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).

Acknowledgements

We are grateful to Andrew Jensen and Walter Siegmund for making their images available for use under a creative commons licence.

We have used the species account given by Jensen (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

  • Jensen, A.S. (2000). Eight new species of Macrosiphum from Western North America, with notes on four other poorly known species. Proceedings of the Entomological Society of Washington 102(2), 427-472. Full text