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Genus Panaphis

Large walnut aphids

Species Overview: Genus Panaphis  Panaphis juglandis 

Genus Panaphis [Calaphidini]

These are large distinctive aphids with short antennae only about 0.3-0.4 times the body length. All viviparous females are winged. The wings have the veins dark bordered with dark spots near the wing margin. The abdomen has dark marginal sclerites, broad dark bands across tergites 3-7, broken ones across tergites l - 2 and a small trapezoid sclerite on tergite 8. The siphunculi are short, truncate and without a flange. The cauda has an elongate oval knob.

There are 3 described species all living on walnut (Juglandaceae). They typically feed along the midrib of the upper surface of the leaves. They are closely related and could perhaps be geographic variants of a single species. They have a sexual stage in the life cycle, but do not host alternate and are not attended by ants. They can be a serious pest on walnuts.

 

Panaphis juglandis (Large walnut aphid)

All viviparae are alate. The fourth instar nymph (first picture below) has transverse rows of brown patches on the dorsal abdomen. The adult alate (second picture below) is large and stout-bodied. It has a darkened head and thorax, and a yellow abdomen with dark brown transverse bands. The forewing veins are fuscous-bordered. The siphunculi are short and truncate. The body length of the alate is 3.5-4.3 mm.

 

They live on the upper sides of leaves of walnut (Juglans regia), in rows along the veins, and are often ant-attended. Sexual forms occur in September-October. The species is rarely found together with the small walnut aphid, supposedly because it is adversely affected by the rain of honeydew from the other species. It occurs in Europe, and parts of central Asia, Pakistan and was introduced into the western USA.

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

  •  Stroyan, H.L.G. (1977). Homoptera: Aphidoidea (Part) - Chaitophoridae and Callaphidae. Handbooks for the identification of British insects. 2 (4a) Royal Entomological Society of London. Full text 

 

Identification requests

Alan Outen, 4 June 2014

There is a large Walnut tree in the village with foliage partly hanging over the fence and above the footpath. I have been checking this weekly and today, at last, I found a single specimen of Panaphis juglandis - one I was especially keen to see! There can be no doubt of the id of this one I know but one image attached for the record! It was very active and I was chasing it for ages trying to get sharp images - still not completely succesful!