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Genus Phyllaphis [Phyllaphini]
Phyllaphis are medium sized elongate oval, pale yellowish green aphids, covered with wax wool. Wax is produced from well-developed dorsal wax glands. Their antennae are shorter than the body and have a very short terminal process. The siphunculi are pore-like. Winged forms have the abdomen wax-covered, with variably-developed dark dorsal cross-bars.
The Phyllaphis genus contains 2 or 3 species on the leaves of beech (Fagus: Fagaceae). They have a sexual stage in the life cycle, but do not host alternate and are not attended by ants.
Phyllaphis fagi (Woolly beech aphid)
Woolly beech aphids feed on the undersides of a young leaf of beech (Fagus spp.) causing the leaf to curl downwards on both sides of the mid-rib, forming a pseudo-gall (see first picture below). The wingless viviparae of Phyllaphis fagi are elongate oval, pale yellowish green, covered with wax wool (see second picture below). Their antennae are slightly shorter than the body and have a terminal process that is 0.11-0.12 times the length of the base of the last antennal segment. The body length of Phyllaphis fagi apterae is usually 2.0-3.2 mm, but summer dwarfs may be down to 1.1 mm.
Winged viviparae (see third picture above) have the abdomen wax-covered, which largely conceals variably-developed dark dorsal cross-bars.
The woolly beech aphid feeds on the undersides of young leaves of beech (Fagus spp.). This causes the leaves to curl downwards on both sides of the mid-rib, and often to wither and die prematurely. It is distributed throughout Europe, east to Turkey and Caucasus. More recently it has been reported from China and Korea, and introduced to Australia, New Zealand and North America.
Phyllaphis grandifoliae (American woolly beech aphid)
Immature Phyllaphis grandifoliae (see first picture below) are pale yellow-green with abundant fine wax filaments. Adult apterae of Phyllaphis grandifoliae (see second and third pictures below) are pale greenish, pale yellow or somewhat cream-coloured. They are usually covered with white waxy filaments. Antennal segment II is 1.2-1.5 times longer than antennal segment I (cf. Phyllaphis fagi, which has antennal segments I & II more or less equal in length). The dorsum has weakly pigmented spinal, pleural and marginal sclerites on all tergites. On abdominal tergite VIII the bases of hairs are surrounded by wax gland pores in form of cribriform (= pierced with small holes) discs (cf. Phyllaphis fagi, where the bases of the hairs on abdominal tergite VIII are surrounded by wax gland pores in the form of double-contoured rings). Marginal and spinal tubercles are absent. Abdominal tergite VII has 2-4 hairs that are 26-42 μm long. Siphunculi are present as small pores. The cauda is small, rounded or weakly knobbed, with 2 hairs. The body length of adult Phyllaphis grandifoliae apterae is about 1.8 mm.
First two images above by permission, copyright Claude Pilon, all rights reserved.
Phyllaphis grandifoliae is found on American beech (Fagus grandifolia). Sexual forms develop in autumn. The oviparae have pale siphunculi and lack dorsal abdominal cross-bars. The species is found in eastern USA and eastern Canada.