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Aphidinae : Macrosiphini : Ovatus crataegarius
 

 

Identification & Distribution:

The aptera of Ovatus crataegarius is yellow-green to apple-green, sometimes mottled with darker green markings (see first two pictures below on primary & secondary host). Their antennae are curved, and about 1.2-1.5 times as long as the body. The antennal terminal process is more than 5 times the length of the base of antennal segment VI. The antennal tubercles are well developed and their inner faces are apically convergent in dorsal view (see first clarified mount below). The pale or dusky siphunculi taper gradually from base to flange (cf. Myzus persicae, which has the siphunculi slightly swollen over the distal 0.5-0.7 of length). Their siphunculi are 1.7-2.6 times as long as the tongue-shaped cauda. The body length of adult Ovatus crataegarius apterae ranges from 1.5-2.0 mm.

Note:
On their primary host, hawthorn, Ovatus crataegarius fundatrices and apterae are morphologically indistinguishable from Ovatus insitus, a sibling species that host alternates from hawthorn to gipsywort (Lycopus europaeus). However, the spring migrant winged forms can be differentiated (see below).

The Ovatus crataegarius alate (third image above) has a green abdomen with darker green patches. The spring migrant winged forms of Ovatus crataegarius have 22-49 secondary rhinaria on antennal segment III, and 5-20 on antennal segment IV (cf. Ovatus insitus, which have 60-83 secondary rhinaria on antennal segment III, and 36-52 on antennal segment IV). The oviparae of Ovatus crataegarius also have fewer pseudosensoria on their hind tibiae than those of Ovatus insitus.

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

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

The primary host of the hawthorn - mint aphid is hawthorn (Crataegus) and, less commonly, apple (Malus) or quince (Cydonia). In summer this species host-alternates to mint (Mentha), where it can reach pest status. In warmer climates Ovatus crataegarius may occur as an anholocyclic form on mint, overwintering viviparously near the ground. Ovatus crataegarius has a near worldwide distribution, from Europe and the Middle East to Central Asia, India, Pakistan, parts of Africa, the USA, Canada and Brazil.

 

Biology & Ecology

Origin of Ovatus crataegarius

Müller (1980) considers the origin and subsequent evolution of Ovatus crataegarius and Ovatus insitus. These are two sibling species, whose sexuales encounter each other on mutual primary hosts. Comparisons have shown the fundatrices of these two species, as well as their apterous alienicolae (=wingless viviparae on the secondary host), are morphologically indistinguishable. In the other morphs the range of variation of most characters overlap to a high extent, or appear practically identical. Good distinguishing characters exist in the emigrant alatae and in the oviparous females. The emigrant alatae of Ovatus insitus have more rhinaria on their antennae than those of Ovatus crataegarius. It is thought this character reflects the necessity of locating their alternative summer hosts: which are Mentha species in Ovatus crataegarius, and Lycopus europaeus in Ovatus insitus. The oviparous females of Ovatus insitus have significantly more pseudosensoria on their hind tibiae. The differences in these sex pheromone-producing organs may be responsible for the pre-mating reproductive isolation between the two aphids.

A critical examination leads to the conclusion that the genesis of these two species is almost certainly not allopatric (i.e. they have not evolved in geographic isolation). But some authorities consider a sympatric (non-isolated) mode of origin, as a result of occupying ecological niches, is virtually impossible too. The most plausible mode of speciation would be that there were mutational changes in feeding behaviour and in the efficiency for surviving on a new host plant. Müller argues that such changes can bring about enough isolation for sympatric speciation.

Life cycle

In Britain during spring Ovatus crataegarius can be found commonly on hawthorn (see picture below of immatures on hawthorn), and less commonly on apple.

In summer the leaves of their primary host normally harden-up and their levels of soluble nitrogen drop. The aphids respond by developing alatae (see picture below) which migrate to mint.

However, anything which delays the drop in available nutrients delays their departure. Cichoka & Lubiarz (2012) showed that Ovatus crataegarius populations appeared in apple orchards in large numbers if the trees were pruned. We have also found that Ovatus may remain on hawthorn if they feed inside old Dysaphis galls (see picture below). These galls remain green, probably because of the release of cytokinins by the original gall-maker.

Those aphids that do migrate to mint can again be distinguished by their long curved antennae (see picture below).

Leonard (1963) describes the distribution and habits of Ovatus crataegarius in America. Goszczynski et al. (2016 ) found Ovatus crataegarius and Ovatus mentharius on mint plants in greenhouses in Poland. Ovatus crataegarius was an anholocyclic form that overwintered in the greenhouses.

Population dynamics

Jaskiewicz & Slawinska (2004) monitored aphid populations on five Crataegus media trees in park and street sites from 1999-2001 in Lublin, Poland. Four aphid species were found: Aphis pomi, Ovatus crataegarius, Rhopalosiphum insertum (= Rhopalosiphum oxyacanthae) and a Dysaphis species. More aphid species, and larger numbers of aphids, were found on trees in the street-site than in the park-site. Generally Aphis pomi and Dysaphis were commonest, followed by Ovatus crataegarius and Rhopalosiphum oxyacanthae. Ovatus crataegarius (see picture below) was found on hawthorn in May-June through to late July, reaching maxima varying from 7 to 56 aphids per 5 shoots.

One year Ovatus crataegarius (see picture below) was observed again from the end of September through to October.

Natural enemies

Ovatus crataegarius may get attacked by Entomophthora (a fungus genus parasitic on diptera) when on hawthorn (see picture below).

Goszczynski et al. (2016 ) recommended use of the braconid parasitoid Aphidius colemani, the cecidomyiid Aphidoletes aphidimyza, and the neuropteran Chrysoperla carnea for biological control of Ovatus crataegarius in greenhouses in Poland.

 

Other aphids on same host:

Primary hosts

Ovatus crataegarius has been recorded from 14 Crataegus species, 4 Malus species (Malus baccata, domestica, Malus ×micromalus, Malus sieversii) and 1 Cydonia species (Cydonia oblonga).

Blackman & Eastop list 16 species of aphid as feeding on common hawthorn (Crataegus monogyna) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 15 as occurring in Britain (Show British list).

Secondary hosts

Ovatus crataegarius has been recorded from 13 Mentha species.

Blackman & Eastop list 26 species of aphid as feeding on Mints (Mentha spp.) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 17 as occurring in Britain (Show British list).

Acknowledgements

Our particular thanks to Roger Blackman for images of his clarified slide mounts.

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

  • Cichoka, E. & Lubiarz, M. (2012 ). The impact of plant shaping on aphid behavior. Journal of Plant Protection Research 52(2), 202-204. Google Scholar

  • Jaskiewicz, B. & Slawinska, A. (2004). Aphids (Homoptera, Aphidoidea) inhabiting the tree Crataegus x media Bechst. in the urban green area. Part I. The population dynamics. Acta Agrobotanica 57 (1-2), 145-156. Google Scholar

  • Goszczynski, W. et al. (2016). Proposals of biological control of pests in greenhouse cultivation of aromatic plants. Progress in Plant Protection 56(3), 398-403. Full text

  • Leonard, M.D. (1980). The distribution and habits of the mint aphid Ovatus crataegarius (Walker). Proc. Ent. Soc. Wash. 65, 55-62.

  • Müller, F.P. (1980). Ovatus crataegarius (Walker, 1850) und O. insitus (Walker, 1849) als Modell für sympatrische Speziation ohne Inanspruchnahme ökologischer Nischen (Homoptera: Aphididae). Deutsche Entomologische Zeitschrift, 27, 199-217. Abstract