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Aphidinae : Macrosiphini : Pleotrichophorus glandulosus
 

 

Pleotrichophorus glandulosus

Bristly mugwort aphid

On this page: Identification & Distribution Biology & Ecology Other aphids on the same host

Identification & Distribution

Adult apterae of Pleotrichophorus glandulosus are yellowish white or greenish, sometimes with a pale green median stripe (see first picture below) (cf. Pleotrichophorus duponti which is dull greyish green with green transverse stripes). The antennal tubercles are fairly low with divergent inner faces. The antennae and legs are mainly pale with only the apex of the fifth antennal segment, the base of the sixth antennal segment, and the tarsi dark. The antennae have a very long terminal process, 5-9 times the length of the base of antennal segment VI. They have numerous thick, short capitate hairs hairs on the dorsum in 2-3 transverse rows on each segment. The siphunculi are long and slender, cylindrical over most of the length but slightly expanded at the tip with a small flange. The cauda is finger shaped. The body length of the adult Pleotrichophorus glandulosus aptera is 1.4-2.6 mm.

The alate Pleotrichophorus glandulosus (not pictured) has a yellowish abdomen with pale brown marginal sclerites and darker pleural intersegmental sclerites.

The bristly mugwort aphid lives on the undersides of the lower leaves of mugwort (Artemisia vulgaris). It can also be found on other Artemisia species and corn chamomile (Anthemis arvensis). Sexuales are produced in autumn with eggs laid on the leaf undersides. Pleotrichophorus glandulosus is found over most of Europe including Britain, and has been introduced to North America.

 

Biology & Ecology

Life cycle

We have found Pleotrichophorus glandulosus on several occasions mainly on mugwort growing on chalk downland, but also in coastal villages. The life cycle starts in spring when the overwintering eggs hatch to give the viviparous fundatrices. The fundatrix is much like the apterous viviparous females of later generations, but more greenish and with a relatively shorter terminal process, only 3.0-3.5 times the base of antennal segment VI. There then follow several generations of apterous and alate viviparae - we have yet to find alatae, so assume they are comparatively rare.

We have not found Pleotrichophorus glandulosus an especially common species, being present usually singly on only a small percentage of the lower leaves. The group of immatures pictured below was the largest group we have observed on one leaf.

The picture below shows an adult aptera Pleotrichophorus glandulosus with the first instar nymph she has just deposited.

Numbers appear to peak in July August, often remaining (relatively) high into autumn when the sexuales develop. Apterous males (see picture below) start to appear by September.

The males are small (1.7 mm), very slender, yellowish with a brown head and prothorax, and with brown spots and transverse stripes on the abdomen (see picture below). Their antennae are very dark, and the cauda dusky.

The oviparae (see first picture below) have the basal half of the hind tibia brownish, swollen, and bearing 50-60 small scent plaques. The cauda is thicker than in viviparous females, but oviparae are otherwise similar to apterous viviparae.

Their eggs are pale yellow when first laid (as in second picture above), but darken to shiny black over subsequent days.

Interspecific competition and Natural enemies

Many of the colonies of Pleotrichophorus glandulosus that we found were sharing the habitat with large numbers of pointed snails (Cochlicella acuta, see picture below). This is a species which prefers calcareous soils as present in the site where most of these pictures were taken (Malling Down in East Sussex).

Takada (1966) described the new species of parasitoid Lysaphidus pleotrichophori. It parasitizes Pleotrichophorus glandulosus on Artemisia species. The mummies are pale yellowish brown.

 

Other aphids on same host:

Blackman & Eastop list 73 species of aphid (including 28 Macrosiphoniella species) as feeding on mugwort (Artemisia vulgaris) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 27 as occurring in Britain (Show British list).

Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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

  • Takada, H. (1966). Three new aphid species of the genus Lysaphidus Smith from Japan (Hymenoptera: Aphidiidae). Insecta matsumurana 28(2), 127-130. Full text