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Genus Pterocallis

Alder aphids

Species Overview: Genus Pterocallis  Pterocallis alni   Pterocallis maculata 

Genus Pterocallis [Panaphidini]

These are small pale aphids. They have antennae that are shorter than, or as long as, the body with a short terminal process. Their siphunculi are short and truncated. In viviparae the cauda is knobbed and the anal plate is two-lobed.

There are thirteen species of the Pterocallis genus worldwide. There is no host alternation. They feed especially on alder species (Betulaceae: Alnus spp.). They are usually dispersed on the undersides of leaves, and are mostly not attended by ants. Wingless viviparae occur more commonly than in most genera in the Calaphidinae  subfamily.

 

Pterocallis alni (Common alder aphid)

 Both the winged and wingless adult viviparae of Pterocallis alni are yellowish white to yellowish green. Their antennae are ringed with black. The hind femur has a characteristic black spot near its apex. The tarsi are black. The body length of Pterocallis alni apterae is 1.3-2.0 mm.

 

Pterocallis alni is found almost exclusively on common alder (Alnus glutinosa) in Europe, living dispersed on undersides of leaves and sometimes attended by ants. Sexual forms occur in September-November. The common alder aphid is common and widespread in Europe, east to Turkey, Iran and Lebanon and introduced to North America, New Zealand, Australia and Chile.

 

Pterocallis maculata (Green-barred alder aphid)

Adult apterae of Pterocallis maculata are yellowish-green or green, with a pattern of diffuse dark green dorsal cross bands, giving an overall blotchy appearance (see first picture below). The antennae of Pterocallis maculata are short, only 0.6-0.8 times the body length, and have black apices to the antennal segments. The siphunculi of Pterocallis maculata are dark, at least at the tip. There is a black spot near the apex of the hind femur and the tarsi are black. The body length of the aptera is 1.4-2.1 mm. The alate (see second picture below) has a greenish abdomen with dark green markings

 

Second image copyright Alan Outen,  all rights reserved.

Each abdominal segment bear 5 pairs of pigmented capitate hairs situated on very pale and inconspicuous round sclerites. The third antennal segment has more than 2 long hairs, and some hairs on the fourth and fifth antennal segment are longer than the basal diameters of their respective segments.

Pterocallis maculata lives on the undersides of the leaves of alder (Alnus glutinosa and other species) in colonies along the veins. It is nearly always attended by ants. Apterous males and oviparae occur in September-October. The green-barred alder aphid is quite rare in Britain, but is widely distributed in Europe, east to Turkey and Iran.

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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).

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