Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Scarce Maple AphidOn this page: Identification & Distribution Biology & Ecology Damage & Control
Identification & Distribution:All Drepanosiphum aceris viviparae are alate. Winged adult females (see pictures below) are yellowish or pale whitish-green with dark thoracic lobes. There are often rather narrow cross-bands on abdominal tergites 4 and 5 (just visible viewed through the wings), and usually lateral spots in front of their siphuncular bases. The siphunculi are dark (not black) at least distally. The forewing has a dark spot at the wing-tip and another (less clear) at the outer end of the pterostigma. The body length is 2.7-4.2 mm.
The scarce maple aphid lives on field maple (Acer campestre), usually under leaves near ground. Sexual forms occur in September-November. Drepanosiphum aceris is distributed throughout Europe and east to the Caucasus.
Biology & Ecology:
The overwintering eggs of the scarce maple aphid laid the previous autumn on twigs and branches hatch in spring, and the aphids develop in compact colonies. The image below shows a third instar nymph with the developing cross bands bright green at this stage.
The first image below shows an alatiform (winged-form) fourth instar nymph of Drepanosiphum aceris.
The second image above shows a teneral (recently moulted) alate which lacks any dark markings.
The image below shows a mature adult alate with the black cross bands clearly visible.
Drepanosiphum aceris is described as local by Stroyan (1977) , and we have only found it two or three times. It is certainly much less common per unit leaf-area of field maple than Drepanosiphum platanoidis is per unit area of sycamore - despite both aphid species being similar in size. This does not appear to support the suggestion of Gaston & Lawton's (1988) that similarly sized species should show the same general level of abundance since they have similar per-capita resource requirements.
Dixon & Kindlmann (1990) suggest that abundance of different aphid species depends more on the abundance of their hosts. However, at least in East Sussex, field maple and sycamore are similarly abundant - so this also does not explain why Drepanosiphum platanoidis is so much commoner than Drepanosiphum aceris.
There seem to be few records of predators and parasitoids apart from Wiackowski et al. (2001) who recorded Aphidius rosae as a parasitoid of this species. They are certainly predated by syrphid larvae, as shown by the syrphid egg found with an alate vivipara of Drepanosiphum aceris and two young nymphs shown below.
The close-up below shows the characteristric microsculpture of syrphid eggs.
Damage and control
Drepanosiphum aceris colonies do seem to result in premature yellowing of the leaves that they inhabit, as can be seen by the leaf below. This will result in premature leaf drop.
Field maple is widely grown as an ornamental tree in parks, and the wood is of good quality, but its small size and slow growth means the tree has little commercial value. Hence one cannot consider the scarce maple aphid as a pest, especially since it is usually quite uncommon.