Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Sweetclover aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Apterous viviparae of Therioaphis riehmi are very rare (but see Quednau (2003) for illustration of aptera). Fourth instar alatoid nymphs (see first picture below) are pale yellow whilst alatae (see second picture below) are dark yellow or yellowish-orange. In alate Therioaphis riehmi the antennal terminal process is 0.92-1.1 times the length of the base of antennal segment VI. Antennal segment III bears 9-12 secondary rhinaria. The apical rostral segment (RIV+V) is shorter than the second hind tarsal segment (HTII) (cf. Therioaphis ononidis on Ononis which has RIV+V longer than HTII). Abdominal tergites I-VII each bear 4 hairs, 1 pair spinal and 1 pair marginal (cf. Therioaphis trifolii which has more than 4 hairs on each of abdominal tergites I-VII). These hairs arise from pigmented tubercular bases, giving four longitudinal rows of dark sclerites on the dorsum; the paramedian sclerites are of medium size, oval and in pairs. Wing veins, especially the radial sector, are dark-shadowed. The siphunculi are pale, stump-shaped and flangeless. The cauda has a constriction and a knob-like apex. The anal plate is bilobed. The Therioaphis riehmi body length is 2.0-2.7 mm.
Both images above by permission, copyright Claude Pilon, all rights reserved.
The image below shows young immatures - note the same four dark spots across each tergite.
Image above by permission, copyright Claude Pilon, all rights reserved.
The preferred host of Therioaphis riehmi is melilot, sweet clover (Melilotus spp.), where they feed on leaf undersides. They are also found on species of medick (Medicago spp.), fenugreek (Trigonella spp.) and clover (Trifolium spp.). There is no host alternation and sexuales (oviparae and alate males) develop in September. Although there is the potential for damage to sweetclover crops, such damage only occurs occasionally as natural factors usually depress midsummer populations (Manglitz & Hill, 1964). The sweetclover aphid is indigenous to Europe, North Africa, Middle East, India, Kazakhstan, China and has been introduced to North and South America.
Other aphids on the same host
Therioaphis riehmi has been recorded on 9 species of Melilotus (Melilotus albus, Melilotus altissimus, Melilotus indicus, Melilotus italicus, Melilotus officinalis, Melilotus segetalis, Melilotus suaveolens, Melilotus sulcatus, Melilotus wolgicus)
Therioaphis riehmi has been recorded on 1 species of Medicago (Medicago sativa).