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Aphidinae : Macrosiphini : Macrosiphum daphnidis
 

 

Macrosiphum daphnidis (= Macrosiphum daphinidis)

Daphne aphid

On this page: Identification & Distribution Biology & Ecology Occurence in UK Other aphids on the same host

Identification & Distribution

Adult apterae of Macrosiphum daphnidis (see first picture below) are pale yellowish or whitish green with a slightly darker spinal stripe. Their antennae have the apex of each segment darkened, and the terminal process is 5.9-6.7 times as long as the base of antennal segment VI. The apterae have dark brown eyes (cf. Macrosiphum euphorbiae, which has red eyes). The apical rostral segment (RIV+V) is 0.8-0.9 times as long as the second hind tarsal segment (HTII). The longest hair on the vertex is 61-92 µm (cf. Macrosiphum euphorbiae. which has the longest hair on the vertex 28-48 µm). The longest hair on abdominal tergite III is 43-71 µm (cf. Macrosiphum euphorbiae, where the longest hair on that tergite is 21-37 µm). The femora of apterae are entirely pale, but the tibiae are dark apically. The siphunculi are slightly darker at the apices and have polygonal reticulation on the distal 0.1-0.2 of their length; the siphunculi are 1.8-2.3 times the caudal length. The cauda has 10-19 hairs. The body length of adult Macrosiphum daphnidis apterae is 2.4-4.2 mm.

The alate of Macrosiphum daphnidis (see second picture above) has the abdomen yellowish-green with faint dusky marginal sclerites on segments II-IV. The antennae are 1.2-1.5 times the body length, and have 26-47 secondary rhinaria on ANT III. The siphunculi are dusky and are 1.8-2.3 times the length of the cauda.

The pictures below show clarified mounts of an adult viviparous aptera and a viviparous alate.

Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.

Macrosiphum daphnidis is thought to favour mezereon (Daphne mezereum), but is also found on other Daphne species including spurge laurel (Daphne laureola). It forms small, rather loose colonies on growing buds and shoots, and also scattered on the undersides of leaves where their colour can render them difficult to see (see picture below).

Image above by permission copyright Mark Wilson, all rights reserved.

There is no host alternation, and sexual forms (oviparae and alate males) develop on Daphne in autumn. Macrosiphum daphnidis overwinters as eggs laid on the stems of the host plant. The daphne aphid is found over much of Europe, and has been introduced to north-western USA and Canada.

 

Biology & Ecology

Occurence in UK

Macrosiphum daphnidis is rare in Britain but, so far, has been found in Somerset, Bristol, Surrey, Cambridge and Kent (Watson (1982)). It is easily confused with Macrosiphum euphorbiae which also occurs on mezereon, but the live adult aptera can be distinguished from that species by its brown eyes. Macrosiphum euphorbiae adult apterae have red eyes.

We have never found this species ourselves, nor for that matter have we ever come across the host plant (Daphne spp.). Hence we were delighted to get a report of the aphid from Mark Wilson in Somerset in early June 2021. The aphids were on a planted area of spurge laurel (Daphne laureola) outside the village hall. The picture below shows a first or second instar nymph.

Those below are also immatures in instars II-III. Note the immatures have more reddish-brown eyes.

Some of the immatures were maturing to adult apterae, but many fourth instars had developing wing buds indicating they would produce alatae and would most likely disperse to find new hosts.

The pictures below show an adult aptera with her latest progeny, and an adult alate.

It is thought that the life cycle is also holocyclic in Britain, though no sexuales have been found.

Watson (1982) considered that the more frequent occurrence of the rare host plant Daphne mezereum in calcareous woodlands, and the greater frequency of cultivated Daphne species in the milder climate of southern England were responsible for the aphid being (apparently) restricted to southern England. But she noted that with the increasing interest of the public in planting non-native shrubs, the aphid may well become more common and widespread.

 

Other aphids on the same host

Macrosiphum daphnidis has been reported on 7 Daphne spp. (Daphne x burkwoodi, Daphne cneorum, Daphne indica, Daphne laureola, Daphne x mantensiana, Daphne mezereum, Daphne striata).

Blackman & Eastop list 2 species of aphid as feeding on mezereon (Daphne mezereum) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists both as occurring in Britain (Show British list).

 

Damage and control

The rarity of the species and its use of a relatively unimportant genus of host plants renders it economically unimportant except perhaps to the nursery industry, since leaves fed upon by the aphids tend to senesce and fall prematurely. Kennedy, Day & Eastop (1962) mention Macrosiphum daphnidis being a relatively poor vector of two styletborn viruses of cabbage and cucumber.

Acknowledgements

We are very grateful to Mark Wilson for sending us photos and live specimens of Macrosiphum daphnidis, and to Roger Blackman for images of his clarified slide mounts.

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 Watson (1982) and Roger Blackman & Victor Eastop's Aphids on Worlds Plants 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

  • Kennedy, J.S. et al. (1962). A conspectus of aphids as vectors of plant viruses. 114 pp. Commonwealth Institute of Entomology, London Abstract

  • Watson, G.W. (1982). A biometric, electrophoretic and karyotypic analysis of British species of Macrosiphum (Homoptera: Aphididae). PhD thesis, University of London, 296 pp.