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)

 

 

Identification & Distribution:

Wingless females of Aphis gossypii vary in size and colour depending on conditions. In cool favourable conditions they are medium-sized and blackish green or green mottled with dark green. In hot conditions or when crowded they are smaller and are a very pale whitish yellow. Most commonly they are light green mottled with darker green. The dorsum has no dark sclerotized markings. The siphunculi are dark. The cauda is usually paler than the siphunculi and bears 4-8 hairs. The body length of apterae ranges from 0.9-1.8 mm. Aphis gossypii alates have 6-12 secondary rhinaria distributed on the third antennal segment and usually none on the fourth.

Marginal tubercles are only consistently present on abdominal tergites 1 and 7. The longest hairs on the third antennal segment are 0.3-0.5 times the basal diameter of that segment. The terminal process of the last antennal segment is 1.7-3.2 times the length of the base of that segment. The apical segment of the rostrum is 1.1 to 1.5 times the length of segment 2 of the hind tarsus. Micrographs of whole mounts in alcohol are shown below.

The clarified slide mounts below are of adult viviparous female Aphis gossypii : wingless, and winged.

Micrograph of clarified mounted  aptera (first image) courtesy PaDIL.  Copyright Rebecca Graham (Department of Agriculture, Western Australia) under Commons Attribution 3.0 Australian License.  Alate micrograph (second image) courtesy Favret, C. & G.L. Miller, AphID.  Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO.

The melon or cotton aphid is highly polyphagous and does not usually host alternate, reproducing all year round on its chosen host. In temperate climates it is most often seen in glasshouses on cucurbits (cucumbers and marrows) and begonias, and in gardens on ornamental Hypericum species. In the tropics Aphis gossypii is a major pest of cotton. It is distributed almost worldwide, and is particularly abundant in the tropics.

 

Biology & Ecology:

Aphis gossypii does not have a sexual phase in the tropics, nor in most of Europe. Some sexual reproduction may be taking place in southern France, although the primary host is unknown. Host alternation and a sexual phase occur more regularly in parts of east Asia and in North America. Several unrelated plants are utilised as primary hosts.

Colonies may or may not be ant attended. One colony was found around a leaf petiole at junction of leaf and petiole of Hypericum androsaemum - no ants were attending the colony, but a Myrmica ant was feeding at an extra-floral nectary on the plant as shown in the picture below:

 

On other occasions ants were definitely attending the aphids, as shown below with a Lasius niger ant.

Aphis gossypii is very variable in colour. The picture below shows a 'normal' coloured Aphis gossypii (mottled green) along with some darker aphids. It seems likely that the darker aphids were also Aphis gossypii, since Aphis fabae is not recorded from this Hypericum species.

Alternatively this may be a mixed species colony. Our photos have revealed many examples of mixed species colonies, but these are seldom referred to in the literature and there has been little if any work on the dynamics of such colonies. Hill (1987)  points out that many ecological studies have failed because of the inability of the observer/recorder to recognise a mixed species population.

This particular colony had several predators actively reducing its numbers, including the syrphid larva shown above.

 

Damage and control

In temperate climates Aphis gossypii is considered an important pest of greenhouse crops such as cucurbits and ornamentals such as Begonia and calla lily (Zantedeschia aethiopica). Insecticide treatment may be recommended. Outdoors it is a pest of Hypericum androsaemum and Hypericum inodorum. Leaves may turn yellow and on ornamentals the large amounts of honeydew and exuvia may look unsightly. Soap solution may be used to reduce numbers. In the tropics it is a major pest of many crops including cotton, cucurbits, coffee, cocoa, peppers and okra. Aphis gossypii is known to transmit over 50 plant viruses.

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

  •  Blackman, R. L. & Eastop, V. (2006). Aphids on the World's Herbaceous Plants and Shrubs. Vols 1 & 2. J. Wiley & Sons, Chichester, UK. Full text 

  •  Hill, D.S. (1987). Agricultural insect pests of temperate regions and their control. CUP, Cambridge.

  •  Stroyan, H.L.G. (1984). Aphids - Pterocommatinae and Aphidinae (Aphidini). Handbooks for the identification of British insects. 2 (6) Royal Entomological Society of London.

 

Identification requests

Patrick Roper 23/7/2014

I have attached a photo of a colony of what seems to be (following the account on your web site) Aphis chloris.

Image copyright Patrick Roper  all rights reserved.

As well as my rather inconclusive photo, I have examined the insects with a high powered lens and they certainly agree with the general colour and configuration of your web site photos.

The ants, Lasius niger, are in constant attendance which would seem to be characteristic of true A. chloris rather than the unnamed lookalike. This and a nearby colony are on a plant of Hypericum androsaemum.

These aphids and ants occur in what I call my window box wildlife reserve where I have also recently recorded Aphis farinosa, again using your web site. The box has now been going for nearly nine years and I manage it mainly by watering in dry weather. It started as bare earth, so all species have found their way there under their own steam. Hopefully I will now be able to add to the aphid list.

There is a blog here: windowboxwildlife.blogspot.co.uk

If you have time I should be interested in your views on the Aphis chloris colony.

Bob, Influentialpoints:

  • Your aphids on Hypericum are in fact Aphis gossypii, and not Aphis chloris.

    The aphids on that page of our website were unfortunately misidentified.

    Aphis chloris lives low down at the base of the plant and (as far as we know) is restricted to Hypericum perforatum. The aphid we pictured - Aphis gossypii - lives high up on the stem and flowers - like the ones you found.

    We will correct the website in the near future. [Now done.]

    Which reminds me, I ought have said why our initial identification was problematical.

    Aphid keys generally assume you are using 'clarified permanent mounted specimens' which very few people have the facilities, staff, and cash to do (in UK at least) - hence most practising entomologists use wet preps in alcohol - and mistakes do happen...

Patrick Roper 5/8/2014

I have attached another picture of the Hypericum aphid. As you will see, the colonies are expanding.

Image copyright Patrick Roper  all rights reserved.

Bob, Influentialpoints:

  • Your Aphis gossypii on the Hypericum are certainly doing well! They're a bit blacker than ours but Aphis gossypii does vary greatly in colour.