Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Bedstraw witches-broom aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Ant attendance Natural enemies Other aphids on the same host
Identification & Distribution
Feeding by Myzus langei causes a characteristic deformation of the host plant, bedstraw (Galium), such that the stem internodes are greatly shortened hence the foliage is bunched together in the form of a 'witches broom' (see first picture below). Adult apterae of Myzus langei (see second picture below) are flattened, dull yellowish to pale green with a suffusion of rosy red around the postero-marginal portions of the abdomen (note that Stroyan 1950 appears to be incorrect, at least for apterae, when he says that it is the antero-marginal portions that are rosy red). The antennae are short, a little less than half body length, with the terminal process less than 1.5 times as long as the base of antennal segment VI (cf. Myzus ornatus, which has the terminal process 1.9-2.4 times the length of the base of antennal segment VI). Antennal tubercles are absent (cf. Myzus persicae and Myzus ascalonicus, which both have antennal tubercles). The dorsum is strongly scabrous. There is a blunt median process on tergites VIII similar to the supracaudal process of Cavariella, but less developed. The siphunculi are longer than the cauda (cf. Staegeriella necopinata, which has siphunculi only 0.5-0.8 times as long as the cauda). The siphunculi are subcylindrical, slightly incurved for most of their length and markedly constricted towards the apex where they are curved outwards. The cauda is triangular, slightly constricted at the base and bears 4 hairs. The body length of Myzus langei apterae is 1.3-1.9 mm.
The alate Myzus langei (see third picture above) is not as flattened as the aptera and lacks the scabrous cuticle. The head and thorax are dark brown and the abdomen is dirty green suffused to a greater or lesser extent with rosy pink, with a large dark sclerotic patch from tergites IV-VII apart from a membranous patch between the siphunculi and small areas in front of the siphunculi. The siphunculi are dark and more slender than those of the aptera; they are nearly straight apart from a slight outcurving at the apex.
Myzus langei feeds on bedstraw (Galium spp.), especially hedge bedstraw (Galium mollugo). New growth is stunted and deformed so that the foliage becomes bunched like a "witches' broom". Colonies are attended by ants. The bedstraw witches-broom aphid is found in north-west, northern and central Europe, south to Italy and east to west Siberia and Kazakhstan.
Biology & Ecology
As far as is known, Myzus langei does not host alternate, but remains on bedstraw all year. However, Bladmineerders report that Wojciechowski found it on Prunus avium, which could be a so far unrecognised primary host.
We have found large colonies of Myzus langei on hedge bedstraw in mid-May, mainly apterae together with their immatures. Contrary to what was reported by Stroyan (1950), most of the immatures found in May were green rather than rosy red (see picture below).
There were a few rosy red immatures (see picture below) - but all of these had developing wings. It seems therefore that immature alatae are pink, whilst immature apterae are green.
By July nearly all the immatures were destined to be alatae (see picture below).
Some presumably dispersed, but many alatae remained feeding on the same plants. The alatae varied somewhat in colour with some bright rosy pink (see first picture below) and others mainly dirty green with a few pink areas (see second picture below).
Borner (1952) reported that sexual morphs develop in autumn, but these have not yet been described.
Stroyan 1950 noted that the presence of Myzus langei in the bunches of foliage of bedstraw was indicated by the coming and going of ants which attend the species. Colonies on chalk grassland at Birling Gap, East Sussex were usually attended by a Myrmica species of ant (see picture below).
Colonies on chalk at West Dean, East Sussex and in heathland at Ashdown Forest in East Sussex were attended by Lasius ants, most likely Lasius niger (see pictures below).
Zikic et al. (2012) recorded the parasitoids Trioxys galiobii & Aphidius matricariae parasitizing Myzus langei on Galium lucidum.
Other aphids on the same host
Myzus langei has been recorded on 8 Galium species (Galium album, Galium boreale, Galium intermedium, Galium lucidum, Galium mollugo, Galium palustre, Galium saxatile, Galium verum).
Myzus langei has also been recorded from Asperula-cynanchica.