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Identification & Distribution

Adult apterae of Ovatus insitus in spring (on hawthorn, see first picture below) and early summer (on the leaves of gypsywort, see second picture below) are shining green, greenish yellow or greenish white with pale siphunculi (cf. Ovatus crataegarius which is a somewhat darker green). Later generations in August on the stem bases and rhizomes of gypsywort are mottled brown with dark siphunculi (see second clarified mount picture, below). The antennal terminal process is 1.0-1.5 times longer than antennal segment III (mostly less than 1.3 times) (cf. Ovatus crataegarius which has that process 1.1-2.1 times longer than antennal segment III, and usually more than 1.3 times, albeit this difference does not hold for early spring apterae on hawthorn).

The alate Ovatus insitus (see third picture above) has a green or brownish green abdomen with pale siphunculi (possibly dusky siphunculi when developing late in the year). Antennal segment III bears 25-83 secondary rhinaria (rarely less than 43), segment IV has 9-57 (rarely less than 18), and segment V has 1-24 (rarely less than 6) (cf. Ovatus crataegarius in which antennal segment III has 11-52 secondary rhinaria, but rarely more than 43; segment IV has 2-24, but rarely more than 20; and segment V has 0-9, but rarely more than 5).

The clarified slide mounts below are of adult viviparous female Ovatus insitus: wingless on primary host, wingless on secondary host (late summer) and winged.

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

The hawthorn-gypsywort aphid (Ovatus insitus) has hawthorn (Crataegus), medlar (Mespilus germanica), quince (Cydonia oblonga), plus a few other related species as its primary host. Ovatus insitus feed on the underside of young leaves and are almost indistinguishable from the closely related hawthorn-mint aphid (Ovatus crataegarius). The alatae migrate in June to gypsywort (Lycopus europaeus). According to the available literature, they feed on the stem bases and rhizomes of gypsywort - but in early June we have found them on the young aerial shoots of gypsywort. Ovatus insitus is found throughout most of Europe, south-west and central Asia and Siberia.

 

Biology & Ecology

Life cycle

We discussed the origin of the two sibling species as proposed by Müller (1980) in our page on Ovatus crataegarius. Briefly it is believed that the origin of the two species is almost certainly not allopatric (=due to geographical seperation). The most plausible mode of speciation would be the occurrence of mutational changes in feeding behaviour and in the ability to survive on a new food-plant. Such changes may bring about sufficient isolation for sympatric (=not geographically isolated) speciation.

We have (as far as we know) only found the hawthorn-gypsywort aphid once, because nearly most of the Ovatus we have found have been on the primary host, hawthorn, where it is impossible to distinguish Ovatus insitus from Ovatus crataegarius. Whilst Ovatus crataegarius host alternates to mint, Ovatus insitus moves to gypsywort (Lycopus europaeus). Gypsywort (see picture below) is a straggly perennial plant with hairy, oval to elliptical toothed leaves that grows in wet places.

We found Ovatus insitus on the young leaves of gypsywort at Warnham Nature Reserve in early June when there were numerous alatae (see picture below), presumably migrants from hawthorn.

There were also many immatures, mostly the offspring of nymphs deposited by the immigrant alatae.

By June some of those nymphs had matured to adult apterae and were themselves depositing nymphs.

We have yet to return to the site later in the year to check if Ovatus insitus do indeed move to the stem bases and rhizomes.

Natural enemies

Rakhshani (2012) recorded a small wasp, Aphidius matricariae, parasitizing Ovatus insitus on quince (Cydonia oblonga) in May in Iran. He also found a series of mummified Ovatus insitus on the leaves of apple trees. The mummies were black and of globular shape. No parasitoids emerged from them after two years, indicating the presence of obligatory diapause which would normally be broken after overwintering in natural conditions. It was suspected that the parasitoid was Pseudopauesia prunicola, the only known univoltine parasitoid on fruit trees. Ölmez & Ulusoy (2012) recorded Monoctonus mali parasitizing Ovatus insitus on Cydonia oblonga) in Turkey in December. Ferara & Mustata (2005) recorded Ephedrus campestris parasitizing Ovatus insitus on quince in Romania in May.

 

Other aphids on the same host

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

  • Ferara, E. & Mustata, G. (2005). Species of parasitoids that control the populations of aphids (Homoptera: Aphididae) from some orchards in Iasi and Vaslui counties. pp. 75-86 in Lucrarile simpozioului "Entomofagii si rolui lor in pastrarea echilibrului natural" Universitatea "ALL Cuza" Full text

  • Müller, F.P. (1980). Ovatus crataegarius (Walker, 1850) und O. insitus (Walker, 1849) als Modell fur sympatrische Speziation ohne Inanspruchnahme okologischer Nischen. Deutsche Entomologische Zeitschrift 27 (4-5), 199217. Abstract

  • Ölmez, S. & Ulusoy, M.R. (2012). A survey of aphid parasitoids (Hymenoptera: Braconidae, Aphidiinae) in Diyarbakir, Turkey. Phytoparasitica 31(5), 524-528. Full text

  • Rakhshani, E. (2012). Aphid parasitoids (Hymenoptera: Braconidae, Aphidiinae) associated with pome and stone fruit trees in Iran. Journal of Crop Protection 1(2), 81-95. Full text