InfluentialPoints.com
Biology, images, analysis, design...
Aphids Find them How to ID AphidBlog
"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

Search this site

Aphidomorpha : Aphididae : Thelaxinae
 

 

Subfamily Thelaxinae

Biology and Morphology

On this page: Biology Morphology Genera

Biology

The subfamily Thelaxinae has 18 species in 4 genera (Glyphina, Kurisakia, Neothelaxes, Thelaxes). They feed on oaks (Fagaceae), birches and alders (Betulaceae) - except Neothelaxes, which feeds on Parthenocissus (Vitaceae). There is no host alternation and all species are holocyclic.

Thelaxes suberi apterae and nymphs.

In some species immature sexual forms are produced in early summer, but then aestivate until autumn when mating takes place, and eggs are laid. All species are ant-attended.

Thelaxes dryophila colony attended by Formica rufa.

All species are Holarctic.

 

Morphology

Adult Thelaxinae viviparae may be apterous or alate (but apterous viviparae of Neothelaxes are undescribed). Apterae of Thelaxinae have eyes of only three facets (triommatidia) and no distinct line of demarcation between head and thorax. All adult morphs have 5-segmented antennae ornamented with close-set rings of fine spinules, and a short antennal terminal process. The dorsum has extensive sclerotisation, which is sometimes segmentally divided. There are no wax glands The siphunculi are rather large pores placed on low cones. The cauda is either broadly rounded or knobbed (depending on the genus), and the anal plate is rounded, never bilobed.

Thelaxes dryophila dorsal in alcohol.

Thelaxinae alatae have antennae with a few almost circular secondary rhinaria on the antennal segment III. The forewing media is a once-branched, and the hind wing has only one oblique vein. They hold their wings flat at rest, the forewings being stiffened by a proximal extension of the pterostigma, uniting the main vein and costa to form a thick scaly band along most of the front edge of the wing.

Thelaxes dryophila alate.

Thelaxinae Genera

Genus Glyphina [Thelaxini]

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.

Species overview

 

Genus Thelaxes [Thelaxini]

The wingless viviparae are small (1 - 2.3 mm) oval and brown or greenish, sometimes with a paler stripe along the back. The rostrum is distinctive in having a long and almost needle-like last rostral segment. The cauda is knobbed and the siphunculi are very short and virtually pore-like.

There are 4 species which feed on the young shoots, leaves and young acorns of various oak species (Quercus: Fagaceae). Three are in Europe and the Mediterranean region, and one in North America. They have a sexual stage in the life cycle, but do not host alternate. They are usually attended by ants.

Species overview

 

Acknowledgements

We particularly thank Colin Favret and Roger Blackman, who have provided invaluable assistance. Most of the subfamily diagnoses have been taken from Heie & Wegierek (2009b), Quednau (1999, 2003, 2010) and Blackman & Eastop (2021), with additional material from Russell (1982),Stroyan (1977), Stroyan (1984) and many others listed in the references for these pages.

Note: Any images on pages that are not individually credited are copyright InfluentialPoints under a Creative Commons Attribution License.

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