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Lachnus longirostris

Scarce variegated oak aphid

Identification & Distribution  Biology & Ecology  Damage & Control 
Note: Lachnus longirostris was originally confused in the literature with Lachnus iliciphilus, a species of southern France. There is some evidence that Lachnus longirostris is conspecific with Lachnus pallipes  but, until this is confirmed, we continue to treat them as separate species.

Identification & Distribution:

Apterae of Lachnus longirostris are shining dark reddish to blackish brown. The siphuncular cones are rather small. The abdominal dorsum is densely haired with long, fine-pointed hairs. The middle parts of the tibiae are pale and the antennae are 0.4 - 0.5 times the body length. In addition the hind tibia has hairs on the ventral side which are often longer and finer distally, but not with some hairs 2-3 times longer than others. Lachnus longirostris alatae have a pattern of forewing pigmentation similar to Lachnus roboris but with a more extensive clear area between Rs and media. Body length is 2.4 - 5.0 mm.

 

The first image shows the shining blackish-brown Lachnus longirostris aptera. Note especially the hairy dorsum and the pale middle parts of the tibiae. These characteristics can be used to distinguish both apterae and alates of Lachnus longirostris from Lachnus roboris  on oak. In addition the wing patterning of alates is slightly different.

Scarce variegated oak aphids are found on twigs and branches of oak (Quercus spp.). A very similar species Lachnus pallipes occurs on beech. The differences between the two species are mostly size-related and they are considered by some authorities to be the same species feeding on different hosts. Lachnus longirostris is widely distributed in Europe.

 

Biology & Ecology:

The overwintering eggs of Lachnus longirostris hatch in early summer and develop into small colonies. We have only found this species once and then in low numbers. The images below shows a young colony in late June. The aphids are nearly always attended by ants, most often it seems by Formica spp. But in this case the aphids were very assiduously tended by jet black ants (Lasius fuliginosus).

There is little published information on this species. Lubiarz (2007)  reported that over three years of research on Lachnus aphids on oak, Lachnus longirostris was only recorded twice with a total count of only 7 females. Lachnus roboris on the other hand occurred regularly and in large numbers.

The scarce variegated oak aphid has a sexual stage in its life cycle. Oviparae and small apterous males develop in October. Egg laying takes place in autumn after mating.

 

Damage and control

The aphid certainly causes feeding damage by rupture of the tree cambium, but since it is rather uncommon, it is unlikely that control of this aphid would ever be considered.

Acknowledgements

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

  •  Lubiarz, M. (2007). Dynamics of numbers and bionomy of Lachnus roboris (L.) on pedunculate oak (Quercus robur L.) in natural and degraded landscape. Aphids and Other Hemipterous Insects 13 (1), 129-135. Full text