Myzocallis myricae

Identification & Distribution:

Immature bog myrtle aphids are bright yellow with longitudinal rows of pale centred dark spots. Adult Myzocallis myricae alates are yellow or orange, with additional black longitudinal markings on the head and thorax. The antennae of bog myrtle aphids are shorter than their body, and the terminal process of their sixth antennal segment is less than twice the length of its basal part. The abdominal tergites 1 to 7 have paired dusky spinal and marginal sclerites. Myzocallis myricae siphunculi are short truncated cones. The tibiae have similar pigmentation to distal parts of the femora. Their body length is less than 3.5 mm.

The pictures below are micrographs of alcohol-preserved specimens of a winged adult (dorsal view) and a Myzocallis myricae nymphs (lateral view).

Myzocallis myricae does not host alternate but feeds only on bog myrtle (Myrica gale). It is largely restricted to northern and western Europe. Sexual forms occur in autumn.

Biology & Ecology:

Little has been published on the ecology or distribution of this aphid other than that it has been recorded quite widely in Ireland (Carter et al., 1987). In Scotland we found sparse aphid colonies on both the leaves (see pictures above) and hidden in the young shoots (see picture below).

The bog myrtle aphid does not seem to form dense colonies, but prefers instead to space-out over the leaf or shoots (see picture below).

Short-winged (brachypterous) specimens are common. As a result, Myzocallis myricae has, been used in a study into the cost in terms of resources for an aphid of developing flight muscles (Dixon & Kindlmann, 1999). The brachypterous form (with very short or rudimentary wings) of the bog myrtle aphid is structurally very similar to the macropterous form (with long or large wings). It has small but perfect wings but lacks flight muscles. The gonads of the brachypterous form make up a significantly greater proportion of their dry mass than do the gonads of the macropterous form. This conforms the prediction that migrants should have smaller gonads than nonmigrants.

Other aphids on same host:

Myzocallis myricae has been recorded from 1 Myrica species (Myrica gale).

Blackman & Eastop list 5 species of aphid as feeding on bog myrtle (Myrica gale) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015) lists 2 as occurring in Britain: Macrosiphum euphorbiae and Myzocallis myricae.

Acknowledgements Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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 Carter et al. (1987). Species, host plants and distribution of aphids occurring in Ireland. The Irish Naturalists' Journal 22(7), 266-284. Abstract Dixon, A.F.G. & Kindlmann, P. (1999). Cost of flight apparatus and optimum body size of aphid migrants. Role of plant abundance in determining the abundance of herbivorous insects. Ecology 80(2), 1678-1690.  Full text