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Aphididae : Aphidinae : Macrosiphini : Semiaphis
 

 

Genus Semiaphis

Semiaphis aphids

On this page: Semiaphis dauci

Semiaphis [Macrosiphini]

Semiaphis are greenish aphids, usually lightly wax powdered. The median and antennal tubercles are present, but weakly developed. The antennae are 6-segmented (rarely 5-) and about half the body length. Secondary rhinaria are usually absent in apterous females, but present on antennal segments III and IV of alate females. There is no dark dorsal patch in either apterae or alatae, with the abdominal dorsum membranous apart from dark cross bands on the posterior tergites. There are occasionally marginal tubercles present on abdominal segments II-V. The siphunculi are about half the body length, shorter than the cauda, without a flange, and positioned between abdominal segments V and VI. The cauda is tongue shaped or triangular with 5-7 hairs.

Semiaphis is a Palaearctic genus with 14 species worldwide. Some host alternate with Lonicera as the primary host and members of the Asteraceae as secondary hosts. Other Semiaphis species are monoecious on Lonicera or members of the Asteraceae. Two species have moved to Impatiens.

 

Semiaphis dauci (waxy carrot aphid)

Adult apterae of Semiaphis dauci are pale blue-green with a grey head and waxy bloom. Their antennae are 0.4-0.5 times the body length with a terminal process that is 1.7-2.5 times as long as the base of antennal segment VI. The longest hair on antennal segment III is shorter than half the basal diameter of that segment. The apical rostral segment (RIV+V) is as long as or shorter than the length of the second hind tarsal segment. There are dark dorsal cross bands on tergites VIII and VIII. Hairs on the body and appendages are very short; the posterior hair on the hind trochanter rarely exceeds 20μm, and is less than 0.5 times the diameter of trochantro-femoral suture (cf. Semiaphis heraclei on many Apiaceae, including Daucus in Asia, which has that hair greater than half that diameter). The first segment of the hind tarsus has only 2 hairs (cf. Semiaphis anthrisci on Torilis in Europe, which usually has 3 hairs on the hind tarsus). There is no supracaudal process (cf. Cavariella spp., which possess a supracaudal process). The siphunculi are quite short and flangeless, only about 0.5 times the length of the cauda or less, with their apertures slanted towards mid-line. The cauda is tongue shaped, about 1.3 times as long as its basal width. The body length of adult Semiaphis dauci apterae is 1.3-2.1 mm.

Both images above by permission, copyright Dirk Baert, all rights reserved.

The alate Semiaphis dauci has a green abdomen with dark dorsal cross bands on tergites VIII and VIII and marginal sclerites. Antennal segment III has 17-22 secondary rhinaria, IV has 3-6, V has 0-1. The siphunculi are strongly curved.

The most frequent host of Semiaphis dauci is wild or cultivated carrot (Daucus carota), but it is also recorded from several other genera of the Apiaceae including ground elder (Aegopodium) and alexanders (Smyrnium). On moon carrot (Seseli spp.) it occurs as a recognised subspecies, Semiaphis dauci ssp. seselii. The feeding site in spring is on the upper sides of rolled young leaves and leaflets; later in the year they may be found in the umbels. Sexuales (oviparae & alate males) usually develop in autumn, although anholocyclic populations occur in southern England. Semiaphis dauci is found in Europe, North Africa, the Middle East, Central Asia and possibly the USA.

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Acknowledgements

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and sp accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

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References

  • Blackman, R.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.