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Identification & Distribution

Adult apterae of Aphis verbasci are bright golden-yellow to pale-green and slightly wax-powdered (see first two pictures below). The apical rostral segment is very narrow, only slightly tapering and about 3.5-5.0 times as long as its basal width. Bands may occur on tergites 7-8, but may be absent. There is also a pair or irregular dark pleural sclerites on tergite 5 in front of the siphuncular bases - these are just visible in the two adult apterae in picture below, but are clearer in older adults. The black siphunculi are rather heavily built, strongly tapering and usually with a distinct outward curvature at the extreme base. The dark cauda of Aphis verbasci is short and tapering.

Second image above copyright Dr László Érsek, all rights reserved.

Aphis verbasci alates (see picture below) have marginal sclerites on tergites 2-4, postsiphuncular sclerites, strong bands across tergites 7-8 and a small irregular median sclerite on tergite 6. Immature apterae & alatae are similarly coloured to the adults (green or yellow) with dark siphunculi.

The mullein aphid's main hosts are mullein (Verbascum spp.) and buddleia (Buddleja spp.), but it also feeds on Eryobotria japonica, Lantana camara, and Scrophularia spp. The aphids live under the basal leaves and on the developing seeds. Sexual forms (oviparae and wingless males) develop in October. Aphis verbasci is found in Europe east into Russia, the Middle East, North Africa, Central Asia and Northern India.

 

Biology & Ecology:

Habitat

Large colonies of Aphis verbasci develop on the underside surface of the basal leaves of Buddleja (see first picture below) or Verbascum (see second picture below) especially those leaves lying directly on the ground.

Some also move to the flower spike post flowering (see picture below) where they exploit the nutrients being sent by the plant to the developing seeds.

Life cycle

The life cycle of Aphis verbasci is described by Kanturski et al. (2014). Eggs are protected from the effects of winter under the dead leaves of the host plant until spring. The fundatrices which hatch from the eggs reproduce parthenogenetically and viviparously.

Very large populations of this aphid can build up on their hosts. The picture below from Budapest in Hungary shows one such large colony on the underside of a buddleia leaf in early summer.

Image copyright Dr László Érsek, all rights reserved.

Kanturski et al. (2014) reported considerable seasonal differences in coloration. By mid-summer, the large colonies of parthenogenetic females of Aphis verbasci are mainly golden-yellow in colour (see picture below).

Alatae seem to be commonest in mid-summer, although they still do not seem to be very frequent. The first picture below shows three immature alatae and the second shows a mature golden-yellow alate.

By autumn apterae are much paler with coloration varying from pale yellow to pale green (see picture below).

The bisexual generation begins to appear in October. They are of a dark green-olive colour and are more or less densely coated in white wax powder. The males (see first picture below) have 5-segmented antennae and well developed dorsal sclerotization.

First image above copyright Jochem Kuhnen, all rights reserved

The oviparae (see second picture above) are characterized by longer and wider genital plate (a phenomenon which also occurs in other subfamilies of aphids such as the Chaitophorinae), and are slightly sclerotized on abdominal segments IV and V. After copulation orange eggs are visible in the female's body (see pictures above and below).

The oviparous females tend to be more numerous than the males, probably because they have a longer lifespan. The picture below shows some more heavily waxed oviparae from the Netherlands.

Guest image copyright Jochem Kuhnen, all rights reserved.

Each ovipara lays 2-3 big, orange eggs (see picture below) on the lower surface of the leaf.

A few days after deposition the eggs darken to black (see Aphid Eggs- Biology & Morphology) - the picture below shows large clusters of eggs on common figwort (Scrophularia nodosa ) in The Netherlands in October 2020.

Guest image copyright Jochem Kuhnen, all rights reserved.

The pigment in these eggs is located in the tough, membranous chorion which is completely covered with a thin transparent, adhesive coat secreted by the female when the egg is deposited (Peterson, 1962). Upon exposure to air it hardens and glues the egg to the plant stem.

Ant attendance

Aphis verbasci colonies produce large amounts of honeydew visible in the picture below.

Despite the abundance of honeydew, we only found few ants (Lasius niger) attending the aphids (see picture below).

Natural enemies

The colonies may be attacked by a variety of predators and parasitoids. A coccinellid larva is visible in one of pictures above, and the picture below shows numerous parasitized mummies. These were most likely the parasitoid Lysiphlebus fabarum which is a species commonly recorded for Aphis verbasci (e.g. Tomanovic et al. (2009)).

Image copyright Dr László Érsek, all rights reserved

In the East Sussex colonies there were relatively few signs of predator activity, except for a single black parasitized mummy shown in the picture below, most likely an Aphelinus parasitoid.

 

Other aphids on same host:

Acknowledgements

We especially thank Dr László Érsek in Hungary, and Jochem Kuhnen in The Netherlands, for permission to use several of their images.

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

  • Kanturski, M. et al. (2014). Sexual morphs and biology of Aphis verbasci Schrank (Hemiptera: Aphididae). Zootaxa 3755(5), 485-490. Full text

  • Peterson, A. (1962). Some eggs of insects that change colour during incubation. The Florida Entomologist 45 (2), 81-87. Full text

  • Tomanovic, Z. et al. (2009). Regional tritrophic relationship patterns of five aphid parasitoid species (Hymenoptera: Braconidae:Aphidiinae) in agroecosystem-dominated landscapes of southeastern Europe. Journal of Economic Entomology 102(3), 836-854. Full text