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Muscaphis aphidsOn this page: Muscaphis cuspidati escherichi
Muscaphis aphids are very small, oval, shiny brown or green aphids living on mosses. The apterae lack antennal tubercles and the median frontal tubercle. The antennae are short, 5 or 6-segmented, with a pointed terminal process that is as long as or longer than the base of antennal segment VI. Secondary rhinaria are absent. Hairs on the body of adult apterae are short & sparse. First tarsal segments have 2 or 3 hairs. The dorsum is sclerotic with granulate sculpturing. The siphunculi are scabrous, tapering from a somewhat swollen base. The siphunculus aperture is sometimes subapical, in which case it tapers to a narrow rounded apex. The cauda is short with a broad base and a narrow apex. Alatae have longer, 6-segmented antennae with numerous protruding secondary rhinaria on segments III-V. The dorsum is unsculptured with dusky often fragmented abdominal bands. The siphunculi are smoother and more cylinidrical than in apterae. The nymphs of alatae, and fundatrices have numerous hairs on the dorsum, some of which are very long and wavy.
There are 9 species in the world. It is likely that all species host alternate somewhere in their range, but most species are only known from either their primary host (Crataegus, Sorbus) or their secondary host (mosses). There are 6 species in North America and 3 in Europe/Asia. Some of these have a Holarctic distribution.
Muscaphis cuspidati (Pointed spear-moss aphid) Northern Europe
Adult apterae of Muscaphis cuspidati (see first picture below) are dark greenish brown, with a shiny black dorsum and siphunculi, and brown antennae and legs (cf. Muscaphis escherichi, which are shiny red-brown, ochreous or olive brown). The body is broad, oval and somewhat flattened. The antennae are usually 5-segmented, about half the body length, with a distinctly tapering terminal process, 1.2-1.5 times the base of antennal segment V (cf. Muscaphis escherichi, which has the terminal process 0.6-1.2 times the base of segment V; and cf. Muscaphis musci, which has the terminal process 2.0-3.3 times the base). Antennal hairs are small and fine. The rostrum is short, reaching about the mid-coxae, with the apical rostral segment about as long as the second hind tarsal segment. The dorsum of the head and body is entirely sclerotic except for the first two thoracic and last abdominal segments. It is coarsely sculptured with blunt papillae, especially on the head and body margins, where they form hydrofuge (=hydrophobic, water-repellent) tracts which retain an air film when the aphid is submerged in water. The siphunculi are large horn-shaped structures, about 2.5 times the caudal length, bluntly pointed with small, inconspicuous, preapical pores on the outer side. The cauda is blunt finger-shaped with two pairs of fine lateral hairs. The body length of adult Muscaphis cuspidati apterae is 0.9-1.3 mm.
Images above copyright Anders Albrecht, under a Creative Commons Attribution 3.0 License.
The alate Muscaphis cuspidati (not pictured) does not have a papillate dorsal cuticle. The antennae are about 0.75 times the body length, and the terminal process is 1.6-2.2 times the base of the last antennal segment. Secondary rhinaria are distributed 15-24 on antennal segment III, and 4-13 on segment IV (for 6-segmented antennae, there are 5-7 on segment V). The ovipara (see second picture above) is similar to the apterous vivipara, but has much thicker hind tarsi, most likely covered with scent plaques. There is also a special overwintering nymphal form which has the dorsum mostly sclerotic with numerous papillae. Antennae are 5-segmented, about 0.6 times the body, with the terminal process about 2 times the base of the apical segment. Siphunculi are converging, about 0.13 times the body, with apertures on the outer sides close to the apices. Body length is about 0.9 mm.
Muscaphis cuspidati is monoecious on mosses (Calliergonella cuspidata, Drepanocladus aduncus, Brachythecium rivulare). They feed on the moss close to or below water-level. The aphid can live submerged, apparently because the papillate sculpturing of the cuticle is able to trap a layer of air around the body. Muscaphis cuspidati is generally considered to be anholocyclic, and some of the population undoubtedly overwinter as the special overwintering nymphal form. However, Albrecht (2015) pictures an ovipara identified as this species on Brachythecium rivulare. This finding is problematic since many (if not all) Muscaphis species use mosses as secondary hosts, and oviparae should occur on the primary host. So far males have not been described, so it remains uncertain whether holocyclic populations persist, and if so on which host, but it seems very likely that somewhere they do. Muscaphis cuspidati is known from several northern European countries, including Finland, the Czech Republic, England and Germany.
Muscaphis escherichi (Rusty moss aphid) Holarctic
The Muscaphis eschirichi fundatrix (not pictured) on their primary host, Sorbus, is purplish black with rather shiny black siphunculi. The second generation are almost all alatae. It is presumed they leave the Sorbus for their secondary hosts, mosses (but see note below). In northern Russia this happens from late June to early August. These emigrant alatae have large numbers of protruberant transversely-oval secondary rhinaria on their antennae (32-53 on segment III, 19-38 on segment IV and 10-28 on segment V). The siphunculi of both the fundatrices and alatae are long, black and truncate, with a large terminal aperture.
Apterae of Muscaphis escherichi (see two pictures below) on the secondary host (mosses) are shiny red-brown, ochreous or olive brown with legs and antennae slightly paler (cf. Muscaphis cuspidati which is dark greenish brown, with a shiny black dorsum). The dorsum is mostly reticulate. The antennae are 0.5-0.6 times as long as the body, with the terminal process 0.95-1.05 times as long as the base of the last antennal segment. Antennal hairs are very short. The apical rostral segment (RIV+V) is 1.2-1.5 times the second hind tarsal segment (HTII) (cf. Muscaphis cuspidati, which has RIV+V 0.9-1.2 times RIV+V). The siphunculi are narrowly conical, slightly dorsoventrally flattened, tapering towards a rounded apex, and with a small, subapical aperture. The cauda is covered by abdominal tergite VIII; its basal part is broad, the distal part slender.
First image above copyright Anders Albrecht, second image copyright CBG Photography Group;
Alatae produced on the secondary host (not pictured) have 15-20 secondary rhinaria on antennal segment III, 7-11 on segment IV, and 5-6 on segment V.
The host-alternating 'population' (Favret's Muscaphis escherichi ssp. drepanosiphoides) is assumed to have Sorbus as its primary host and mosses as its secondary host. There remains some doubt about this because, although the species is found on many species of mosses, the only successful transfer experiment has been to the moss Plagiothecium. The sexual phase on Sorbus apparently occurs in northern continental Europe, Czech Republic, Russia, Canada and North Korea. In northern Russia gynoparae and males appear on Sorbus in late August, and mature oviparae are present in September-October. The populations on moss in England are thought to be anholocyclic.