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Cinara fornacula

Large green spruce aphid

On this page: Identification & Distribution Biology & Ecology Other aphids on the same host Damage & Control

Identification & Distribution

Adult apterae of Cinara fornacula are pale translucent green, or less commonly pale brown or orange. They are usually lightly wax-dusted ventrally and laterally. The antennae are mainly yellow-brown but apices of segments V and VI are dark. The hairs on antennal segment III are about the same length as the diameter of that segment. The legs are mainly pale yellow brown with pale hairs, but the tips of the tibiae and the tarsi are dusky or dark, as are the terminal segments of the rostrum (cf. Cinara atripes and Cinara rara which have at least the hind tibiae uniformly pigmented). The second hind tarsal segment is exceptionally long and curved, about equal to or longer than antennal segment III. The siphuncular cones are very pale, no darker than the abdomen (cf. most other Cinara species on spruce (Picea) which have the siphunculi darker than the abdomen). The cauda and anal plate are dusky. The body length of adult Cinara fornacula apterae is 3.1-4.5 mm.

Both images above, by permission, copyright Claude Pilon, all rights reserved.

Cinara fornacula feeds at the base of the needles on current-year twig growth of several species of spruce, including white spruce (Picea glauca), black spruce (Picea mariana), blue spruce (Picea pungens) and red spruce (Picea rubens). These aphids are usually found in small numbers, and do not form large colonies. They may be attended by ants, although not closely. The males are alate, and the ovipara has a pericaudal wax ring. The distribution of Cinara fornacula is boreal and Nearctic - Foottit & Maw (1997) give it as Alaska to Newfoundland, down to Colorado to Pennsylvania.

 

Biology & Ecology

Summary descriptions of the morphology and biology of Cinara fornacula are given in Bradley (1961), Hottes (1961) and Foottit & Maw (1997).

Bradley (1961) notes that the fundatrices of Cinara fornacula are solitary, though sometimes two may be found together on the same twig. Subsequently the nymphs produced by apterous or alate females tend to remain with the adult female, forming small clusters.

Joussellin et al. (2013) studied the phylogenetic relationships between American and European Cinara species with a view to understanding the processes that contribute to reproductive isolation and speciation. One of the American species included in the study was Cinara fornacula. The phylogeny of the genus was assessed via their mitochondrial, nuclear and Buchnera aphidicola DNA sequence fragments analysed using a DNA-based method of species delimitation. The phylotype maps for the Cinara species covered in the study are given in Fig 3 of their paper. Cinara fornacula, Cinara hottesi, Cinara sitchensis and Cinara vandykei (plus a few unknown species) were in the Nearctic Picea group (Group 14), and Cinara pilicornis & Cinara pruinosa were in the closely related Palearctic Picea group (group 13).

The main driver of speciation between the American and European species groups was clearly geographic separation. But within those groups other factors came into play, reflected in the apparent similarities of specific European and American species with respect to feeding site and predator defense strategy. For example, the American Cinara fornacula (see first picture below) and the European Cinara pilicornis (see second picture below) both feed on the current years growth of spruce (Picea) and are usually found in small numbers, rather than forming large colonies.

First image above copyright Claude Pilon, by permission, all rights reserved.

Both species rely heavily on crypsis to reduce predation, with the green form matching the colour of the needles, and the brown form matching the colour of the stems. Neither species is closely ant attended, but ants may be found in the vicinity of aphids gleaning honeydew from the surrounding needles. Bradley reports the ants attending Cinara fornacula as Dolichodera plagiatus, Formica fusca, Formica subnuda, and Lasius alienus.

Another species pair is the Nearctic Cinara hottesi and the Palaearctic Cinara pruinosa. Both live on woody twigs of spruce in spring, but throughout the summer can be found feeding in large colonies on the trunk. They are vigorously antennated by ants, and the ants provide protection from predators. There is little attempt at cryptic coloration other than for the young nymphs.

Jousselin et al. concluded that their reconstructions of the history of the genus Cinara and phylotype inferences depicted a global diversification scenario where speciation processes are strongly constrained by host genus association. Each Cinara clade associated with a particular host genus that is naturally present on both continents encompasses both Nearctic and Palearctic Cinara species. In two of the most diverse Pinaceae genera (Pinus and Picea), geographic clustering of species at continental scales is observed. This pattern of distribution suggests repeated independent evolution of Nearctic and Palearctic lineages in each 'host genus cluster' via large scale geographic isolation. Even so, about half of the speciation events were accompanied by ecological niche shifts.

One interesting addendum is that, as with many other aphid species, Cinara pilicornis is now found outside its native Palaearctic territory, having been introduced to Australia, New Zealand and North and South America. What impact this will have in the long term on a species like Cinara fornacula that occupies the same niche remains to be seen. Both species are found on Picea abies, Picea engelmanni, Picea pungens, Picea rubens and Picea sitchensis, but the invasive Cinara pilicornis has not so far been found on Picea glauca or Picea mariana. Perhaps Cinara fornacula is destined to be more restricted to Picea glauca and Picea mariana in future.

 

Other aphids on the same host

Cinara fornacula feeds on 7 species of spruce (Picea): Picea abies, Picea engelmanni, Picea glauca, Picea mariana, Picea pungens, Picea rubens and Picea sitchensis.

 

Damage and control

We can find no references to Cinara fornacula causing any significant damage to spruce trees, so it is likely that numbers normally remain low as a result of the actions of natural enemies.

Acknowledgements

We are especially grateful to Claude Pilon for pictures of Cinara fornacula (for more of his excellent pictures see).

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors 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).

Useful weblinks

References

  • Bradley, G.A. (1961) . A study of the systematics and biology of aphids of the genus Cinara in Canada.PhD thesis, McGill University, Montreal, Canada. Full text

  • Foottit, R. & Maw, E. (1997). Aphids (Homoptera: Aphidoidea) of the Yukon. pp. 387 404 in H.V. Danks and J.A. Downes (Eds.), Insects of the Yukon. Biological Survey of Canada (Terrestrial Arthropods), Ottawa. 1034 pp. © 1997. Full text

  • Hottes, F. (1997). A review and key of North American Cinara (Homoptera: Aphididae) occurring on Picea. Great Basin Naturalist 21(3), 35-50. Full text

  • Jousselin, E. et al. (2013). Is ecological speciation a major trend in aphids? Insights from a molecular phylogeny of the conifer-feeding genus Cinara. Frontiers in Zoology, 10:56. Full text