Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Lipaphis are small to medium-sized greyish or brownish green aphids which are sometimes wax powdered. The antennae are shorter than the body and are without secondary rhinaria in the apterae. The dorsum of apterae is sclerotic with varying degrees of pigmentation. The siphunculi are cylindrical or slightly swollen on the distal part. The cauda is broad-based, tongue shaped or elongate triangular with 4-6 hairs. The alatae may have a complete series of abdominal cross bands or may have such bands only on the posterior tergites.
Lipaphis aphids feed without host alternation on members of the cabbage family (Brassicaceae).
Lipaphis alliariae (Grenade aphid, Garlic mustard aphid)
Adult apterae of Lipaphis alliariae have a blackish or dark blue-green dorsum with four longitudinal series of dark patches (see pictures below). The patches are clearly defined in immatures, but much less so in adults. The antennal terminal process is 1.2-1.35 times the length of the siphunculi (cf. Lipaphis erysimi which has the antennal terminal process 0.8-1.15 times the length of the siphunculi). The third antennal segment is 1.0-1.8 times the length of the siphunculi (c.f. Brevicoryne brassicae which has the third antennal segment 2.5-3.7 times the length of the siphunculi). Abdominal tergites 1 and 7 are without marginal tubercles. The siphunculi are slightly swollen and are 1.1-1.6 times the length of the cauda (cf. Brevicoryne brassicae which has siphunculi 0.8-1.0 times as long as the cauda). The body length of adult Lipaphis alliariae apterae is 1.6-2.1 mm.
Second image above copyright Stéphane Claerebout, all rights reserved, with thanks to Willem Ellis of Plant Parasites of Europe
Lipaphis alliariae feeds on the stems, seed pods and senescing leaves of garlic mustard (Alliaria petiolata). It does not host alternate. Sexual forms, wingless males and oviparae, occur in October. The grenade aphid (presumably so-called because of the resemblance of the aphid in dorsal view to a hand grenade) has a rather patchy distribution in Europe, occurring in France, Sweden, Finland, Poland and Germany, but (at least until 2018) not in Spain, Italy, Britain or Norway. In September 2018 we found the aphid for the first time in Britain feeding on senescing leaves of Alliaria petiolata growing at Jordans Mill in Bedfordshire. Lipaphis alliariae has been seen both as a minor pest and as a potential biological control agent depending on whether its host plant is viewed as a (minor) food crop or a weed.
Lipaphis erysimi (Wild crucifer aphid)
Adult apterae of Lipaphis erysimi are small to medium sized yellowish green, grey green or olive green aphids, with a faint white wax bloom. In humid conditions they may be more densely coated with wax. The aptera (see first picture below) has two rows of dark bands on the thorax and abdomen which unite into a single band near the tip of the abdomen. The siphunculi are paler than the cauda and have dark tips. The discriminant function: 'x= length of antennal segment III + length of terminal process' is usually less than 2.4 times the length of the siphunculus (cf. Lipaphis pseudobrassicae in which that discriminant function 'x' is more than 2.4 times the length of the siphunculus). The body length of adult Lipaphis erysimi apterae is 1.4-2.4 mm.
Second image: Lipaphis erysimi alate, copyright Alan Outen & Rothamsted Research, all rights reserved.
Alatae (see second picture above) have a black head and thorax and a dusky green abdomen with black bands near the tip and conspicuous dark marginal sclerites. The body length of Lipaphis erysimi alatae is 1.4-2.2 mm.16:21 05/12/2018
The wild crucifer aphid does not host alternate. It feeds on various different Brassicaceae, including Brassica, Raphanus, and Sinapis species, although it is not usually found on field Brassica crops. It lives on the undersides of leaves as well as on inflorescences, young shoots and growing points. Males have been found in some countries. Lipaphis erysimi is confined to Britain and northern continental Europe.