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White dead nettle aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Natural enemies Other aphids on the same host
Identification & Distribution
Adult apterae of Cryptomyzus alboapicalis (see first picture below) are pale greenish or yellowish, sometimes with green transverse intersegmental stripes or a median stripe. Their antennae are much longer than the body, and the antennal terminal process is more than ten times as long as the base of antennal segment VI (cf. Cryptomyzus ballotae, which has the terminal process 5.9-9.0 times the length of the base of antennal segment VI). The body and appendages have numerous thick, capitate hairs. The siphunculi are slightly swollen and only 1.0-1.5 times as long as the cauda (cf. Cryptomyzus ballotae, Cryptomyzus korschelti and Cryptomyzus maudamanti, which have their siphunculi 2.1-4.0 times the length of the cauda; also cf. Cryptomyzus galeopsidis, which have siphunculi 1.1-2.1 times the length of the cauda, not very different from Cryptomyzus alboapicalis, but rarely found on Lamium album). The body length of Cryptomyzus alboapicalis apterae is 1.6-2.9 mm.
Alates of Cryptomyzus alboapicalis (see second picture above) have a dark brown dorsal abdominal patch, deeply indented along the sides. The micrographs of Cryptomyzus alboapicalis below are (1) a lateral and (2) ventral view of an aptera in alcohol.
The clarified slide mounts below are of an adult viviparous female Cryptomyzus alboapicalis : wingless, and winged. Note especially the capitate hairs on the dorsum and appendages characteristic of the genus Cryptomyzus, and the short siphunculi relative to caudal length characteristic of this particular species.
Cryptomyzus alboapicalis feeds on the undersides of the lower leaves of white dead nettle (Lamium album) and occasionally on other related species. It does not host alternate, and it is not attended by ants. Over much of its range oviparae and males are produced in autumn, and the species overwinters in the egg stage, but in Britain sexuales have not been recorded, and reproduction is thought to be entirely parthenogenetic. Cryptomyzus alboapicalis is found in Britain and across northern and central Europe to western Siberia and the Caucasus.
Biology & Ecology:
We have found viviparae of Cryptomyzus alboapicalis in southern England on white dead nettle in every month of the year. The first picture below shows an adult aptera in March 2015 which was depositing nymphs.
Perhaps more surprisingly in East Sussex we have found numerous alatae and fourth instar alatoid nymphs in mid-winter (11th January, see picture below). This was despite the fact that the year in question (2019) was not an especially mild winter.
Populations of Cryptomyzus alboapicalis appear to peak in early spring (March/April) before declining in summer and then increasing again in late autumn. The adult aptera below was part of a large colony found in November 2020.
There seems little doubt that, at least in southern England, most of the population overwinters as viviparae. Elsewhere in colder climes sexual forms are produced and the population overwinters in the egg stage.
Guldemond (1990a) studied the evolution of host plant relationships and life cycles of Cryptomyzus species in Europe. As regards Cryptomyzus alboapicalis he recognised two closely related taxa - one feeding on Lamium album, and the other on Lamium maculatum. The latter form was subsequently assigned the name of Cryptomyzus ulmeri. Guldemond (1990b) showed that host plant preference of the two taxa promoted their reproductive isolation.
Basilova et al. (2008, 2010) analysed the karyotypes of the seven Cryptomyzus species found in Europe. Cluster analysis produced two main clusters: One consisted of Cryptomyzus alboapicalis and Cryptomyzus galeopsidis together with Cryptomyzus leonuri and Cryptomyzus ulmeri. The other comprised only species using Ribes as a winter host, namely Cryptomyzus korschelti, Cryptomyzus maudamanti and Cryptomyzus ribis.
The early population peak enables the aphids to exploit a relatively predator- and parasitoid-free period, but fungal infections sometimes take a heavy toll (see two pictures below).
Despite its lifelike pose, the adult aphid in the picture above is very dead, having been recently killed by a rapidly developing entomopathogenic fungal infection. The immature in the foreground is still alive. The picture below shows a more mature infection with the fungus sporulating.
Predators and parasitoids are more in evidence from late April onwards. The image below show a syrphid larva predating Cryptomyzus alboapicalis later that year, in May.
Various Aphididine parasitoids have been recorded as attacking Cryptomyzus aphids including Aphidius ribis, Diaeretiella rapae, Ephedrus cerasicola, Ephedrus lacertosus, Ephedrus plagiator, Lysiphlebus testaceipes, Praon lemantinum, Praon volucre and Toxares deltiger. We have found only a few mummified Cryptomyzus alboapicalis, one of which is shown below - unfortunately no parasitoid emerged from this mummy, so a definite identification was not possible.
Given the appearance of this mummy, it is most likely to be an Aphidius species. Aphidius ribis is the only member of this genus known to attack Cryptomyzus spp., but the only records so far seem to be from the redcurrant aphid (Cryptomyzus ribis) and the blackcurrant aphid (Cryptomyzus galeopsidis) which live on shrubs rather than herbaceous vegetation.
Other aphids on same host:
Cryptomyzus alboapicalis has been recorded from 4 Lamium species (Lamium album, Lamium amplexicaule, Lamium maculatum, Lamium purpureum).
Blackman & Eastop list 24 species of aphid (10 of which are Cryptomyzus) as feeding on white dead nettle (Lamium album) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 17 as occurring in Britain (Show British list).