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Genus Glyphina

Birch thelaxids

Species Overview: Glyphina Glyphina betulae Glyphina pseudoschrankiana

Genus Glyphina [Pterocommini]

These are rather small aphids (body length about 2 mm). The dorsum is pigmented usually greenish or blackish with many conspicuous hairs. The antennae are very short. The siphunculi are present as pores on small cones.

There are 5 species which feed on Alder (Alnus) or Birch (Betula). The 3 Palaearctic species feed on aerial shoots, whereas the two North American species apparently feed underground. They have a sexual stage in the life cycle, but do not host alternate. They are usually attended by ants.

 

Glyphina betulae (Green birch thelaxid)

Wingless viviparae of Glyphina betulae are dark green to almost black with a pale spinal stripe and four pale spots. The antennae are short. The dorsum has wart-like cuticular ornamentation and is coated with thick spine-like hairs. Siphunculi are present as pores on small cones. The body length of Glyphina betulae apterae is 1.2-2.0 mm.

 

Glyphina betulae alatae (see second picture above) are dark green, with a dark brown to blackish head and thorax. The immature stages are green. The abdomen bears numerous tubercles and the siphunculi are short and truncated.

The green birch thelaxid does not host alternate but lives in colonies on young shoots of birch (Betula spp.), especially silver birch (Betula pendula). Glyphina betulae may occasionally also be found on alder (Alnus spp.). Winged forms are found from mid-June to late July. They are usually ant-attended. The life cycle is shortened with oviparae appearing in July, and apterous males in August.

Glyphina betulae is found throughout Europe, and across Asia to Japan. It has been introduced to North America where it is now widespread.

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Glyphina pseudoschrankiana (Brown birch thelaxid)

Wingless Glyphina pseudoschrankiana viviparae are dark brown to black with variable white markings, usually two spots on each side and traces of a spinal stripe. The base of the fifth antennal segment is 1.0-1.3 times longer than than the second segment of the hind tarsus. The dorsum has numerous short wrinkles, sometimes appearing reticulated. Closed 'warts' are only ever present on the head and thorax and on lateral and ventrolateral regions of the abdomen. Hairs on the third abdominal tergite are longer than 50 μm. The body length of Glyphina pseudoschrankiana apterae is 1.5-1.8 mm.

 

Alate Glyphina pseudoschrankiana have the third antennal segment with 13-23 hairs (cf. Glyphina betulae  in which the third antennal segment has 8-15 hairs). Immature stages of Glyphina pseudoschrankiana are reddish brown (cf. Glyphina betulae in which they are green). The colour of their immatures is much the easiest way to identify the species of Glyphina, but be aware that mixed species colonies are quite common. Glyphina pseudoshrankiana (feeding on downy birch) was only separated from Glyphina schrankiana (feeding on alder) in the 1980s by Blackman (1989) .

The brown birch thelaxid does not host alternate, but lives in colonies on the young shoots of downy birch (Betula pubescens) and related downy birches. It tends to prefer young trees and is usually attended by ants. The life cycle is shortened with sexual forms occurring in July, and eggs laid in August.

Glyphina pseudoschrankiana occurs in north-west Europe and Japan.

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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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