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Genus Ovatus [Macrosiphini]
Ovatus are small to medium sized greenish aphids, the adult viviparae of which may be winged or wingless. Their antennae are curved and longer than the body with the terminal process more than 5 times longer than the base of antennal segment 6. Antennal tubercles are well developed with the inner faces convergent in dorsal view, and two additional bumps on the head. The siphunculi taper gradually from base to flange and are longer than the cauda. The winged forms have no black central abdominal patch.
There are about 10 palaearctic species of Ovatus, three of which host alternate between hawthorn and apple (Rosaceae: Pyroidea) and mints (Labiatae), while the other Ovatus sspecies live all-year-round on their former secondary hosts. Ovatus aphids are not attended by ants. One species (Ovatus crataegarius) is considered a pest of mint.
Ovatus crataegarius (Hawthorn - mint aphid)
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. 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.
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 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.
Ovatus insitus (Hawthorn-gypsywort aphid)
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 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.
Ovatus inulae (Fleabane aphid)
Adult apterae of Ovatus inulae range from lemon-yellow to pale green in colour. The fused last two segments of the rostrum (RIV+V) are 2.2 - 2.4 times longer than the second segment of the hind tarsus and bears 15-25 small accessory hairs (cf. all other Ovatus species which have a shorter RIV+V with only 2-6 accessory hairs). The head has a well-developed median frontal tubercle, as well as rounded forwardly directed processes on the antennal tubercles, all clearly visible in the first picture below. The body length of adult apterae is 1.0-1.6 mm.
The Ovatus inulae alate (see second picture above) has a pale greeny-yellow abdomen and a brown thorax. Like the aptera, the apical rostral segment (RIV+V) is unusually long - more than 2.2 times longer than the second segment of the hind tarsus (HTII).
Ovatus inulae lives all year round on fleabane (Pulicaria dysenterica). It feeds on the undersides of the leaves and shoot apices, and especially the bases of the flowers. It can also be found on certain Inula and some other Asteraceae species. Sexual forms are produced in the autumn. The species is found throughout Europe into central Asia.
Ovatus mentharius (Mint aphid)
Ovatus mentharius apterae have been described as greenish-white (see first picture below), but pale green with darker green markings may be a better description of the adult aptera. The antennae are as long as, or longer than, the body. The inner sides of the antennal tubercle and the first antennal segment of Ovatus mentharius each have a forwardly directed process. The process on the antennal tubercle is as long as or longer than its basal width in dorsal view. The siphunculi are attenuated and cylindrical on the distal half, and at midlength are about as thick as the hind tibiae at midlength; the siphunculi are 2.0-2.5 times as long as the cauda. The body length of adult apterae of Ovatus mentharius is 1.2-1.8 mm.
The alate viviparous female has the head and thorax brownish, the abdomen green, the antennae black and the siphunculi brownish with paler bases. Immatures (see second picture above) are pale yellow-green.
The mint aphid does not host alternate and lives all year on the underside of leaves of mint (Mentha spp.). It is not attended by ants. Winged males and oviparae can be found in autumn. Ovatus mentharius is found over most of Europe south to Turkey and in central Asia.