InfluentialPoints.com
Biology, images, analysis, design...
Aphids Find them How to ID AphidBlog
"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

Search this site

 

 

Identification & Distribution

Colonies of Paramyzus heraclei live on the undersides of the leaves of their host, common hogweed (Heracleum sphondylium), causing yellow spotting and vaulting (=arching) of the leaves (see first picture below). The adult apterae are shiny white or pale yellow, with dark red eyes (see second and third pictures below). The appendages are pale, apart from the tarsi which are dark. The antennae are much longer than the body with the terminal process 5.0 to 6.1 times the length of the base of antennal segment VI. Antennal segment III has 4-15 secondary rhinaria on the basal half (cf. Myzus ascalonicus and Myzus persicae which have no rhinaria on antennal segment III). The apical segment of the rostrum (RIV+V) is 1.4-1.7 times the length of the second hind tarsal segment (HTII). The siphunculi are long, straight, slightly swollen, and 2.0-2.5 times the length of the cauda. The body length of adult Paramyzus heraclei apterae is 1.3-1.9 mm.

The alate Paramyzus heraclei (see clarified mount below) has a dark head, thorax and antennae, and a white to greenish yellow abdomen. There are dark marginal sclerites on the abdomen, together with a dark dorsal patch on abdominal tergites III-V and other dark markings.

The micrographs below show an apterous Paramyzus heraclei, dorsal and ventral in isopropyl alcohol.

The clarified slide mounts below are of adult viviparous female Paramyzus heraclei: wingless, and winged.

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

The pale hogweed aphid does not host alternate, but remains year round on its host hogweed (Heracleum species). Feeding by the aphid results in small yellow spots and arching of the leaf to produce a shallow cavity within which the aphid lives. Yellow oviparae and alate males are produced in autumn with overwintering eggs laid on the old hogweed plant.

 

Biology & Ecology

Life cycle

The fundatrices of Paramyzus heraclei hatch from the eggs in March from overwintering eggs laid on hogweed stems or leaves. They mature to adults by the end of April. Their population peaks in numbers in mid summer. The sexuales appear in September (Mueller, 1977).

The pale hogweed aphid is very easy to overlook, since in our (admittedly limited) experience of this species they tend to be rather sparsely distributed on the host. We have so far only found apterous viviparae, and those not till late August. They were on young hogweed plants growing in shade on the southern edge of an arable field alongside a small tree-lined river. The aphids were mainly on the underside of the round immature leaves (center of image below), rather than those with a mature leaf-form (once or twice pinnate, hairy and serrated, divided into 35 lobed segments, top-right of image below).

Adult Paramyzus heraclei were scattered around on the leaves, usually with no more than a single adult per leaf. The picture below shows an adult in the process of depositing a first instar nymph on the leaf.

These nymphs did not appear to aggregate, but remained scattered over the leaves feeding where they had been deposited (see picture below of young nymphs on underside of young hogweed leaf).

When the aphids feed on the underside of the leaves of giant hogweed (Heracleum mantegazzianum), Hansen et al. (2007) noted that they are prevented from direct feeding on the leaf veins by the presence of numerous trichomes. These trichomes can be clearly seen in the picture below. However, with Heracleum sphondylium they do sometimes feed on the main veins, perhaps because the trichomes are less dense on Heracleum sphondylium than on Heracleum mantegazzianum.

Colour

Mueller (1977) described two colour forms of Paramyzus heraclei - shining white and pale yellow. They were sampled at Rostock, East Germany from Heracleum sphondylium, and reared in separate cultures in the field insectary.

All the Paramyzus we have found were a very pale yellow. Note in several of the pictures above one can see the red eyes of developing nymphs through the dorsal cuticle of the adult vivipara.

 

Natural enemies

We have not found any active predators attacking Paramyzus heraclei, although the presence of syrphid eggs (see picture below) on the leaves of Heracleum when no other aphid was present suggests syrphid larvae may consume these aphids.

There is almost no information in the literature on natural enemies of Paramyzus heraclei apart from a study by Hansen et al. (2006) who looked at the interactions between giant hogweed (Heracleum mantegazzianum), the myrmecophilic aphid Anuraphis subterranea at the stem base, the attending ants, and two non-myrmecophilic aphid species on the leaves, Paramyzus heraclei and Cavariella theobaldi. The ant Lasius niger improves the leaf envelope capacity (=domatium) of giant hogweed by building above ground soil shelters to lodge colonies of the obligate myrmecophilic aphid Anuraphis subterranea. Controlled by the domatium size, the aphid population cannot seriously harm the plant. Hansen et al. (2006) found a positive correlation between the relative plant growth, the ant activity, and the number of myrmecophilic aphids inside the domatium. On the other hand, two non-myrmecophilic aphid species on the leaves, Paramyzus heraclei and Cavariella theobaldi, reduce the growth of giant hogweed in the native habitats. The ants again limit this damage because there was a negative correlation between ant activity and aphid numbers on the leaves, presumably partly because of predation by ants of the non-myrmecophilic Paramyzus and Cavariella aphids. In other words in this situation three partners - the plant, the ants and the myrmecophilic aphids benefit from the mutualistic relationship simultaneously - only the leaf-feeding aphids 'loose out'.

When it comes to parasitoids, we have found one parasitoid species attacking Paramyzus (see pictures below of an aphid in the process of mummification and of a fully mummified aphid).

The fully hardened mummy is glossy black in colour which suggests that we are looking at an Aphelinus species of parasitoid.

Derocles et al. (2011) found no parasitized Paramyzus heraclei in his study of parasitoid food webs in crops and field margins, but noted that two parasitoid species from this species had been reported in the literature. One of these was Monoctonus caricis.

 

Other aphids on the same host

Paramyzus heraclei has been recorded from 8 Heracleum species (Heracleum dissectum, Heracleum lanatum, Heracleum mantegazzianum, Heracleum maximum, Heracleum moellendorffii, Heracleum persicum, Heracleum sibiricum, and Heracleum sphondylium).

Blackman & Eastop list more than 33 species of aphid as feeding on Heracleum species worldwide, and provide formal identification keys.

Of those, Baker (2015) lists 20 as occurring in Britain: Anuraphis subterranea, Aphis brohmeri, Aphis fabae, Aphis spiraecola, Cavariella aegopodii, Cavariella archangelicae, Cavariella konoi, Cavariella pastinacae, Cavariella theobaldi, Dysaphis crataegi group, Dysaphis lauberti, Dysaphis newskyi, Hyadaphis foeniculi, Hyadaphis passerinii, Macrosiphum euphorbiae, Macrosiphum gei, Myzus ascalonicus, Myzus ornatus, Myzus persicae and Paramyzus heraclei.

Acknowledgements

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 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

  • Darocles, S. et al. (2014). Molecular analysis reveals high compartmentalization in aphid-primary parasitoid networks and low parasitoid sharing between crop and noncrop habitats. Molecular Ecology doi:10.1111/mec.12701 Google Scholar

  • Hansen, S.O. et al. (2006). Mutualistic relationship beneficial for aphids and ants on giant hogweed (Heracleum mantegazzianum). Community Ecology 7(1), 43-52. Full text

  • Hansen, S.O. et al. (2007). Herbivorous arthropods on Heracleum mantegazzianum and H. sosnowskyi, in its native and invasive distribution range. In: Pysek, P.(ed): Ecology and Management of Giant Hogweed (Heracleum mantegazzianum). Cabi Publishing. Google Books

  • Mueller, F.P. (1977). Morphs and biology of Paramyzus heraclei Homoptera Aphididae. Reichenbachia 16(25), 233-240.