372 APHIDS OF THE ROCKY MOUNTAIN REGION 
Alate Sexupara. Body length 1.75-2; hind tibia .65-.70; hind tarsal II .15-.16; antenna 
.60-.65; fore wing 2.6-3. 
Ovipara: Apterous. Body greenish; appendages pale yellowish. Body length .90; an- 
tenna .20; hind tibia .13; hind tarsal II .06. Rostrum wanting. 
Male. Apterous. Pale yellow. Body length .60. Without rostrum. 
Gall. Pale green. The fundatrix gall containing a solitary fundatrix consists of a pocket- 
like gall on upperside of a leaf at the base of the new growth, gall opening on underside, her 
young migrating soon after birth and locating separately near the margins on the underside 
of new leaves, forming a row of pocketlike or beadlike galls each 6-10 in diameter, each con- 
taining a solitary aphid, apterous or alate. The alatae migrate, probably to another tree. The 
apterae produce alate virgogeniae, which form new galls, and in August and September, alate 
sexuparae which develop in the gall with the mother. The sexuales are certainly deposited 
on the Populus, some were found in the galls in October; but certainly not all are deposited 
in the galls since the sexuparae are alate and are found leaving the galls as early as August 9. 
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Mesothoracie Glands 
Fig. 449. Thecabius populi-monilis 
Collections. On Populus angustifolia and P. tamacahaca, rarely on P. sar- 
genti, in galls on leaves (apparently no alternate host existing). Throughout 
region. Fundatrices June 25, apterous and alate fundatrigeniae July 17 to Oct. 
18, alate sexuparae Aug. 9 to Oct. 18, sexuales Oct. 18; rather common. 
Chief Distinguishing Characters. Character of the galls, number of sensoria 
on III (not exceeding 10) and absence of sensoria on VI in alate vivipara and 
vestigial condition or absence of the wax gland plates in alate vivipara. 
Tribe Fordini Baker 
_ Baker, 1920a:77. 
Characters. Antenna five- or six-segmented in alata. Eye of aptera con- 
sisting of ocular tubercle only. Secondary sensoria oval. Wax glands present 
but not well developed. Cornicle absent. Hairs rather prominent to incon- 
spicuous. Fore wing with media simple; hind wing with both media and cubitus. 
Living subterranean, on roots or in the nests of ants. 
Key to Genera of Fordini 
1. Antenna of both alata and aptera five-segmented (p. 372)..............cc-sseccesccescecesecenseeseeees Fo-da 
Antenna of alata six-segmented, aptera four- to five-segmented.................-::cscceceseeeecneseeeeesenes 2 
2. II not longer than I; permanent sensoria with Cilia (p. 374) ..........-:cssscssesesececececeeeseeescees Geoica 
II longer than I; permanent sensoria without cilia (p. 375).::..-...-c-sccssssseseseesececerees Trifidaphis 
~Genus. Forda Heyden 
Heyden, 1937:291; Baker, 1920a:78. 
Characters. Antenna five-segmented in apterous and alate viviparae; 
permanent sensoria without cilia. Cauda bearing many hairs. Cornicle absent. 
Hairs simple. Living subterranean. 
Genotype (monotypical), Forda formicaria Heyden. 
Key to Species of Forda 
1. Hairs on antenna numerous, .04-.05 long, over half as long as diameter of 
antenna; sensoria 30-55 on III in alate vivipara (p. 373) ........:.:s-scssssscecessseceeeeeeeeeeee formicaria 
Hairs on antenna sparse, .01 long, hardly evident; sensoria 11-24 on III 
in alate vivipara (p. 373) ......-..c.00--- ERC A Mana RCS APE Wee al Eee Bele bee 8) olivacea 
