Fundatrices on maple, Cinara on conifers, the polyphagous Myzus clan, aphids on birch and oak, and some monophagous aphids

Weatherwise March has been somewhat unpredictable but with two very mild spells, one in the middle of the month and the other at the end of the month. Maximum temperatures reached about 18 deg C. on both occasions. Combined with high rainfall levels in February, this resulted in ideal growing conditions for plants, and aphids have been taking advantage of this. Some species hatch from overwintering eggs, whilst those that overwinter as viviparae start to reproduce again.
 

Fundatrices on maple - Periphyllus and Drepanosiphum

The common periphyllus aphid, Periphyllus testudinaceus, can be found on nearly all species of maple. Its eggs usually hatch in March to give the bizarrely shaped fundatrices (stem mothers) shown below left. These give birth parthenogenetically (asexually) to the next generation of aphids. You might expect that hatching so early in the year would enable them to mature before most predators become active - in other words it would provide a predator-free temporal refuge. But in fact predators like the spider shown below right and parasitoids still seem to take a heavy toll.

There is even a parasitoid that seems to specialise in parasitizing the developing fundatrices. The parasitized 'mummies' that we found should emerge to give adults in April, if so we'll show them in our next blog. They must have parasitized the fundatrices around the middle of March. Surprisingly we have not found ants attending and protecting Periphyllus fundatrices, despite the fact that later in the year the colonies are often ant attended.

A question for other aphid enthusiasts - are Periphyllus fundatrices ever ant attended? And if not, why not?

The other common maple aphid is the common sycamore aphid, Drepanosiphum platanoidis, which is restricted to sycamore (Acer pseudoplatanus). This species can be superabundant some years, usually in years when there are fewer common periphyllus aphids. They can be easily distinguished from Periphyllus aphids by their long siphunculi projecting from the rear part of the dorsum - those of Periphyllus are short and stump-like. Drepanosiphum aphids also have long prominent antennae.

The very young nymphs of Drepanosiphum platanoidis in the picture above were feeding on the developing sycamore buds before bud break. In early April they will move to the leaves and mature into adult female winged fundatrices. In this species the fundatrix is not easily distinguishable from other winged females. Their offspring mature in June and July, usually into very pale alates which show a remarkable uniformly-spaced pattern of aggregation on the undersides of sycamore leaves.

Cinara aphids on spruce & pine may be wax-off - or wax-on!

Spruce trees have several different species of Cinara aphids. The species we tend to find earliest in the year is the wax-bordered spruce aphid, Cinara pruinosa. This is a colony we found on spruce at Abbotts Wood in East Sussex in mid-March.

They are usually closely attended by ants, as above by southern wood ants (Formica rufa). When it is attended, it seems to have very little wax. However, when unattended, Cinara pruinosa can look very different.

Wax and ant attendance are usually considered to be mutually exclusive defensive strategies against parasitoids and predators. But our observations suggest that Cinara pruinosa can choose - if there are ants present, it does not need to invest energy in producing wax. If no ants show-up to attend the aphids, the aphids secrete wax to protect themselves.

There are several large aphid species on Scots Pine, but two of those most commonly encountered are the Scots pine aphid, Cinara pini (below left) and the large pine aphid, Cinara pinea. We found Cinara pinea in Selwyn Wood in January and in March we found thriving colonies of both species on young Scots Pine at Flatropers Wood, East Sussex. The siphuncular cones of Cinara pini are black, whilst those of C. pinea are brown.

Both species may be attended by ants, but it is much more regular with Cinara pini. This may be because later in the spring Cinara pinea moves to the very young growth, whilst the wood ant Formica rufa prefers to stay on the branches with Cinara pini where it is less likely to fall off.

The polyphagous Myzus clan - the 'little-brown-jobs' of the aphid world

One could argue that Myzus aphids are the most boring of aphids, because they are small or very small, and generally rather nondescript greenish or brownish in appearance. However, the genus contains three highly polyphagous species which are very important pests, namely Myzus persicae, Myzus ascalonicus and Myzus ornatus. All can be found in winter, especially Myzus ascalonicus which is well known for continuing to reproduce parthenogenetically through the winter, and is especially common on bulbs in storage. The aphid below was part of a large colony found on young onion plants in a conservatory.

Being a mild winter, we were not surprised to find Myzus ascalonicus type aphids on many other plant species including ivy-leaved toadflax (Cymbalaria muralis) (below left) and mouse ear (Cerastium tomentosum) (below right) in March. We cannot be certain both these species are ascalonicus until we have examined preserved specimens under the microscope, as there are other less common Myzus species that we might have found such as Myzus cymbalariae.

Myzus ornatus (see picture below) is a rather more distinctive aphid, with a series of conspicuous dark green or brownish transverse bars between each abdominal segment.

Unfortunately it only shows this pattern in the adult stage, and nymphs are indistinguishable from other related species. This aphid often forms multi-species colonies with other species such as Myzus ascalonicus.

Ant saviours on birch and oak: Symydobius oblongus and Lachnus roboris

On deciduous trees there are no Cinara aphids from which ants can obtain honeydew, but there are others that do an equally good job. One of these is the shiny birch aphid, Symydobius oblongus. Their eggs are laid in autumn either singly or in small groups near a bud on its foodplant birch (Betula) - see picture below left.

On hatching, the first instar nymphs of Symydobius oblongus aggregate to form clusters with their batch mates (see picture above right). These particular eggs hatched as soon as we brought them indoors on March 5th, but outside they would normally be speedily attended by a wood ant as soon as they hatched.

This picture shows a wood ant avidly attending a newly hatched Symydobius nymph.

The other common deciduous woodland aphid which is a big honeydew provider is the variegated oak aphid, Lachnus roboris. Unlike Symydobius, this aphid lays its eggs in autumn in very large clusters (see first picture below) with over 500 eggs laid on a single twig. During winter many of the eggs of Lachnus roboris are attacked by predators and pathogens. Blazhievskaya (1980) reported that only 30% of the eggs laid actually hatched.

First instar Lachnus roboris are very active, running away from any perceived threat of danger. They feed on the last year's oak twigs, and are fanatically attended by wood ants, despite the obviously rather small amount of honeydew a first instar can produce. First instars may produce attractive volatiles or honeydew that is especially rich in preferred sugars to attract the ants. This species is called the variegated oak aphid because the adult winged forms have black-and-clear variegated wings, unlike most other aphid species. We will see the adults later in the season.

Some monophagous Aphis species - specializing in just one food plant

The first of these is a species that lives on horehound (Ballota nigra) known as Aphis ballotae (= Aphis balloticola). We found it in Alfriston, East Sussex scattered around the leaves of an old straggly plant that had more-or-less survived the winter.

Aphis ballotae closely resembles (and may indeed be the same species) as Aphis frangulae beccabungae. That species has alder buckthorn (Rhamnus) as its primary host and then moves to speedwell (Veronica beccabunga) and various Lamium species in early summer. The two cannot be distinguished morphologically, and until transfer experiments are done, we will not know if they are indeed the same species. That's the great thing with aphids - there is still so much work to be done just to find out the basic biology of the different species.

We'll close with a fairly well known monophagous aphid, pellitory-of-the-wall aphid (Aphis parietariae) that lives (as you may have guessed) on pellitory-of the-wall (Parietaria judaica). The plant is frequently found growing out of cracks in old walls and pavements, as well as on cliffs and banks, and will often be found with the stems, leaves and flowers covered in aphids, sometimes smothering the plant.

Ants often attend colonies of Aphis parietariae. The ants feed on the abundant honeydew produced by large numbers of aphids. If ants do not attend, the leaves may be covered by sooty moulds growing on the honeydew.

So why 'hunt' for aphids??

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).

Useful weblinks

References  Blazhievskaya, A. P. (1980). The variegated oak aphid and ants. (In Russian). Zashchita Rastenii 1980 No. 1 pp. 37. Abstract