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Chickweed aphid, Sweet william aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same host
Identification & Distribution
Adult apterae of Macrosiphum stellariae are yellowish green, green or red. The antennae have the apices of the segments dark with the terminal process 5.3-6.7 times as long as the base of antennal segment VI. Antennal segment III has 2-9 secondary rhinaria, concentrated near the base of the segment. The fused apical segment of the rostrum (RIV+V) is 0.8-1.0 times the length of the second hind tarsal segment (HTII). The legs are mainly pale but the distal tips of the femora and tibiae are dark (cf. Macrosiphum euphorbiae which has the apical parts of the femora pale or only slightly dusky). The siphunculi are mostly pale, but their apices are frequently as dark or darker than the tips of the tibiae (cf. Macrosiphum euphorbiae which never has the apices of the siphunculi as dark or darker than the tips of the tibiae). The siphunculi are about 0.25 times body length (cf. Macrosiphum penfroense, on Silene maritima, which has the siphunculi 0.3 times the body length); they are 1.8-2.1 times the length of the cauda, with reticulation on the apical 13-18%. The cauda is rather blunt and slightly constricted, with 8-15 hairs. The body length of adult Macrosiphum stellariae apterae is 1.8-4.4 mm. The immatures in the colony we found were heavily wax-dusted (see second picture below, showing an alatoid fourth instar nymph).
The alate Macrosiphum stellariae (not pictured) is similar to the aptera except the head capsule is brown, antennal segments I and II are dusky green-brown, the base of segment II is colourless to green and the rest of the antenna is dark brown or black. Also the prothorax is green, and the mesothorax is green with dark brown sclerites. The femur has the distal quarter dark brown to black, and the siphunculi are dark distally with a black tip.
Macrosiphum stellariae forms small colonies on the young shoots of various members of the pink family (Caryophyllaceae) especially species of Dianthus, Silene and Stellaria, and rarely on some other plants. Sexual forms develop in autumn, although in some countries overwintering is thought to be by parthenogenetic forms. Macrosiphum stellariae is found throughout northern and central Europe, and has been introduced to Canada and New Zealand.
Biology & Ecology
There have been very few studies of either the biology or ecology of Macrosiphum stellariae, despite its large host range and widespread distribution. It is very similar in appearance to the common potato aphid, Macrosiphum euphorbiae, and is likely to often be misidentified as such. We have (knowingly) encountered Macrosiphum stellariae only once - in May on sweet william (Dianthus barbatus). The popular ornamental garden plant is shown below in flower with an adult syrphid (Eupeodes) taking a nectar meal.
There was quite a large colony of aphids over several plants, with numerous immatures and several apterous adults.
The immatures, especially the fourth instars (see picture below), were quite heavily dusted with wax.
Other aphids on the same host