302 APHIDS OF THE ROCKY MOUNTAIN REGION 
Macrosiphum dirhodum (Walker) 
The Rose Grass Aphid 
Aphis dirhoda (sic.) Walker, 1849:43. 
Ooh seo dirhodum, Patch, 1914a:268; Theobald, 1926:135; Gillette and Palmer, 
Myzus haywardi Knowlton, 1942b:5 n. syn. 
Apterous Summer Vivipara. Yellow to pale green, darker on median and lateral lines; 
cauda pale; cornicle pale with dusky tip; legs pale to dusky; antenna pale. Body length 
2.4-2.8; hind tibia 1.2-1.7; hind tarsal II .15-.17; antenna 2-2.6; rostrum attaining 2d coxa. 
Hairs slightly capitate; on side of body .01 and sparse. Cornicle imbricated, without reticula- 
tion. Cauda tapering to rather blunt tip, without distinct neck and bearing 3-4 or, rarely, 
5 pairs of lateral and 1-3 single dorsal hairs. 
Alate Vivipara. Same as apterous vivipara except as follows: Head and thorax yellow- 
brown to brown; antenna blackish beyond base of III; rostrum attaining only to 2d coxa. 
Ovipara. Apterous. Pale lemon-yellow, often mottled with reddish, paler on head; 
antenna pale with distal ends of segments and entire VI dusky; cornicle except tip, cauda and 
tibiae pale; tarsi dusky. Body length 1.80; hind tibia .86; antenna 1.40-1.50. Nearly four-fifths 
of hind tibia swollen, at widest part to about twice the width of narrowest part, and bearing 
numerous sensoria. 
Male. Alate. Head yellow-brown; thorax dark brown; abdomen buff with dark dorsal 
bands, dorsolateral intersegmental spots and lateral areas on all segments; antenna and hind 
tibiae dark brown to blackish, cornicle and cauda slightly dusky. Body length 2; hind tibia 
1.50; antenna 2.60. 
Egg. Newly laid, pale yellowish; later, black. Size .70 by .30. 
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Fig. 359. Macrosiphum dirhodum 
Collections. As winter host, on leaves and twigs of rose (Rosa sp.); as 
summer hosts, on celery (Apium graveolens), oat (Avena sativa), Bromus 
tectorum, Elymus sp., and Phalaris sp. Throughout region. Fundatrices April 
10 to 23; summer apterous viviparae on winter host Oct. 23 to 29, on summer 
hosts July 24 to Oct. 2; alate viviparae (fall migrants) on winter host Sept. 20 
to Dec. 3; on summer hosts June 24 to Nov. 12; oviparae on winter host Oct. 11 
to Nov. 23; males on winter host Oct. 11 to Nov. 23, on summer hosts Oct. 16; 
common. 
Chief Distinguishing Characters. Rostral IV-+V broad and short (.10 long, 
equalling two-thirds length of base of anter.nal VI or hind tarsal II), cornicle 
without reticulation, number of sensoria on III of apterous vivipara (1-2), cauda 
short (.20 on median line) and rather broad without distinct neck, pale yellow 
to green body with darker green mediodorsal stripe and with blackish tip on 
cornicle, rather low frontal tubercles and small number of sensoria on III (1-2 
in apterous vivipara and 18-28 in alate vivipara). 
Theobald (op. cit.) expresses doubt as to the identity of the American and 
European species but fails to state differences except that Theobald’s figure of 
the cornicle of Patch’s species exaggerates the doubtful suggestion of possible 
reticulation in Patch’s figure. Reticulation is absent in the form here treated, 
as is the case also in the European form, and therefore does not constitute a 
character for separation. 
