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Genus Coloradoa

Anthemid aphids

Species Overview: Coloradoa   Coloradoa bournieri  Coloradoa tanacetina 

Coloradoa [Macrosiphini]

Coloradoa are small green or reddish globose (globe-shaped) aphids. They have a very convex frons with no antennal tubercles. Their antennae are always shorter than the body, and the terminal process is always longer than the base of the last antennal segment. The dorsal body hairs are short or very short and are expanded at the tip. The apical rostral segment is acutely pointed with concave sides. The siphunculi vary in size and shape.

There are 29 species of Coloradoa worldwide. They feed without host alternation on members of the tribe Anthemideae in the aster family (Asteraceae). Males are usually small and apterous.

 

Coloradoa bournieri (Cotton lavender aphid)

Adult apterae of Coloradoa bournieri are pale or dirty green with dark apices to the appendages. The siphunculi are clearly swollen (see pictures below). The terminal process of the sixth antennal segment is quite short (see first picture below) being 1.2-1.5 times the length of the base of that segment. The fused last two rostral segments (RIV+V) are 1.2 to 1.5 times longer than the second segment of the hind tarsus (HTII). This last character distinguishes Coloradoa bournieri from Coloradoa absinthii, which has the fused last two rostral segments shorter than the second segment of the hind tarsus. The body length of the aptera is 1.1-1.5 mm.

 

The alate has 8-14 secondary rhinaria on antennal segment three, 4-8 on segment four and 0-4 on segment 5.

Coloradoa bournieri feeds on cotton lavender (Santolina chamaecyparissus) and green cotton lavender (Santolina viridis). No sexual forms are known and the species breeds parthenogenetically through the year. The species is indigenous to Mediterranean Europe and the Middle East where its host plant occurs naturally. It has now been found in Britain, having been recorded from Kew Gardens (coll. Eastop, 1960), Cardiff Bay (coll. Baker, 2008) and Brighton (coll. Brightwell & Dransfield, 2015). It has also been recorded from Argentina (coll. Durante, 2009).

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Coloradoa tanacetina (Tansy leaf-margin aphid)

Adult apterae of Coloradoa tanacetina are yellowish green or greenish yellow-brown, with the tips of the antennae and tarsi dark. The antennal terminal process is 1.4-2.0 times longer than the base of antennal segment 6. The last two fused segments of the rostrum (RIV+V) are 0.9-1.0 times longer than the second hind tarsal segment The longest hairs on abdominal tergite 8 are only 14-24 μm. The siphunculi are cylindrical and 1.3-2.2 times longer than the cauda. The length of the adult aptera of Coloradoa tanacetina is 1.1-2.0 mm.

 

Winged forms (not shown) have 9-15 secondary rhinaria on antennal segment 3, 5-11 on segment 4 and 1-9 on segment 5.

Coloradoa tanacetina feed in the indentations at the leaf margins of tansy (Tanacetum vulgare). Sexual forms of the aphid (pale green oviparae and very small orange-yellow males) occur in September and October. Coloradoa tanacetina are found across northern Europe, and have been introduced to 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 species 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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