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Schizaphis are small to medium sized aphids, ovate to somewhat elongate in shape. The dorsal body cuticle is colourless to smoky and more or less reticulate, sometimes with a transverse dark band across abdominal tergite 8. The siphunculi are cylindrical to slightly tapering. The cauda is blunt finger shaped, from about half as long as, to slightly longer than, the siphunculi. The rostrum is short, not reaching beyond the middle coxae. The forewing of the alate has the media vein only once branched.
The Schizaphis genus has about 40 species, about half of which live all year on grasses (Poaceae). Most of the rest belong to the subgenus Paraschizaphis and live on on sedges (Cyperaceae) and bulrushes (Typhaceae). A few mainly Asian species host alternate, overwintering as eggs on pear (Pyrus) or apple (Malus). More than half the species are European, and the others live in Middle East, Asia, Africa and North America.
Schizaphis agrostis (Bent-grass aphid)
Feeding on grass by Schizaphis agrostis results in conspicuous and characteristic feeding damage to its host, Agrostis species. The leaves turn red or yellow-brown and eventually die off (but note some Agrostis species have naturally reddish stolons). Such feeding damage can be seen in the picture below of a colony of Schizaphis agrostis. The adult apterae are grass-green to yellow-green, with a darker green median dorsal line. Antennal segments I, II and the basal part of III are pale, but the other segments are dark. The antennal terminal process is 2.8-4.0 times as long as the base of antennal segment VI. The apical rostral segment (RIV+V) is 0.75-0.88 times the length of the second hind tarsal segment (HTII) (cf. Schizaphis graminum, which has RIV+V 0.65-0.80 times as long as HTII, and cf. Schizaphis holci, which has RIV+V 0.80-1.00 times HTII). Marginal tubercles are present on abdominal tergites I & VII. The siphunculi and cauda are pale, but the former have a dusky apices. The siphunculi are 1.3-1.5 times the caudal length (cf. Schizaphis holci, which has siphunculi 1.25-1.4 times the length of the cauda). The body length of adult Schizaphis agrostis apterae is 1.4-2.0 mm.
Image above copyright Ed Baker, all rights reserved.
Alatae of Schizaphis agrostis are greenish brown with indistinct abdominal marginal sclerites. Their antennae bear 4-10 secondary rhinaria on segment III, and 0-2 on segment IV. The siphunculi are thinner than in the apterae.
Schizaphis agrostis feeds on a limited number of grass species, mainly velvet bent (Agrostis canina), creeping bent (Agrostis stolonifera) and various meadow grass (Poa) species, especially on plants growing in very dry, sandy spots, as well as in salt marshes or saline meadows. Quite large colonies can be found on the uppersides of leaves, where the aphids usually sit in single rows with their heads towards the stems. They are sometimes ant attended. Alatae are formed in the third generation. Sexuales have been found in October with alate males. The overwintering eggs are laid on the leaves and stems of the host grass species. Schizaphis agrostis is found in northern and central Europe, possible extending to Siberia, and has apparently been introduced to North America.
Schizaphis graminum (Greenbug aphid)
Adult apterae of Schizaphis graminum are small and elongate-oval. The head and prothorax is yellowish or greenish straw-coloured. The rest of the thorax and the abdomen are yellowish green to bluish green with a noticeable darker green spinal stripe. The antennae are uniformly dusky. The antennal terminal process is 2.8-4.7 times the length of the base of antennal segment VI. The apical rostral segment (RIV+V) is 0.65-0.8 times the length of the second hind tarsal segment (HTII) (cf. Schizaphis holci, in which RIV+V is 0.80-1.0 times the length of HTII). The siphunculi are pale with slightly flared and darkened tips and are 1.3-1.7 times the length of the cauda (cf. Schizaphis holci, which has the siphunculi 1.25-1.4 times the length of the cauda). The body length of Schizaphis graminum aptera is 1.3 to 2.1 mm.
First image: Kent Loeffler (Public domain). Second image: Alton N. Sparks (Creative Common Attribution 3.0 Unported license).
Schizaphis graminum alatae have a brownish-yellow head and prothorax, black thoracic lobes and a yellowish green to dark green abdomen.
The preferred hosts are grasses and cereals, where Schizaphis graminum can be a major pest. It causes severe feeding damage - initially yellow or red leaf spots which can lead to leaf and root death. It also transmits several plant viruses including barley yellow dwarf virus. Schizaphis graminum develops sexual forms in cold temperate climates, where overwintering in the egg stage occurs predominantly on Poa pratensis, but it continues to reproduce parthenogenetically wherever the climate allows. Schizaphis graminum is not ant attended. Schizaphis graminum is of Palaearctic origin, but is now widely distributed in southern Europe, Middle East, Central and South Asia, Africa and the Americas. Despite the fact that two alatae trapped in UK had identical DNA sequences to the sorghum-adapted form in the USA, there are no records from field crops in northern Europe.
Schizaphis holci (Holcus grass aphid)
Adult apterae of Schizaphis holci (see first picture below) are greenish yellow or pale yellow usually with a faint darker green spinal stripe. The apical rostral segment (RIV+V) is 0.8-1.0 times the length of segment II of the hind tarsus (cf. Schizaphis agrostis, which has the apical rostral segment 0.75-0.88 times the length of segment II of the hind tarsus). The siphunculi are pale with dark tips (cf. Metopolophium dirhodum, which has the siphunculi completely pale). The siphunculi are 1.25-1.4 times the length of the pale cauda (cf. Schizaphis agrostis, which has the siphunculi 1.3-1.5 times the length of the cauda). The body length of adult Schizaphis holci apterae is 1.6-1.9 mm.
The alates of Schizaphis holci (see second picture above) are brownish-green in colour with black-tipped siphunculi.
Schizaphis holci is found on the undersides of leaves of Yorkshire fog (Holcus lanatus) and creeping soft grass (Holcus mollis). Colonies are usually attended by ants. Oviparae and apterous males develop in late September and October. The species is found over much of northern and western Europe; it is rare in UK but is perhaps overlooked.
Schizaphis scirpi (Bulrush aphid)
Apterae of Schizaphis scirpi are shiny dark bronze-brown to reddish brown or blackish. The third segment of the antenna is dark with long fine hairs up to 3-4 times longer than the basal diameter of the segment. The longest hairs on abdominal tergite 3 are 0.10-0.13 mm long. The siphunculi are about twice as long as the cauda. The body length of Schizaphis scirpi apterae is 1.5-2.8 mm.
Guest images copyright Sandy Rae, all rights reserved.
The bulrush aphid lives in ant-attended colonies at the leaf-bases of bulrushes (Typha spp.) and bur-reed (Sparganium spp.). They also occur on sedges (Carex, Eriophorum, Scirpus) and sometimes on other water plants. European populations on cottongrass (Eriophorum spp.) are considered to be a subspecies, Schizaphis scirpi ssp. eriophori They do not host alternate. Oviparae and winged males develop in the autumn. Schizaphis scirpi are found throughout Europe, and in south-west Asia.