286 APHIDS OF THE ROCKY MOUNTAIN REGION 
The genus Macrosiphum is here used in the broad sense. The numersus 
genera into which the genus has been split by various authors are here regarded 
as possibly subgenera and no attempt has here been made to separate these 
groups or to designate which species would be included under each name. 
The genus Illinoia Wilson which has been given rather wide usage is not 
based on a valid morphological distincticn (see Gillette, 1927:347). The original 
description gives no distinguishing characters from those upon which Macro- 
siphum is based. The type species, liriodendri (Monell) shows no generic dif- 
ferences from rosae (Linnaeus); the figure by Baker (1920, pl. VIII, j) showing 
the cauda, the shape of which has been used as the chief distinguishing char- 
acter, was drawn from an immature individual and is therefore erroneous and 
misleading. 
Key to Species of Macrosiphum 
1.0 “Corniche? not: reticulate dic:cesciooocei scab oac seca ac ce secdete none te seetseceskecbe neces teas Os ae ee eaa ae eer 2 
ates, (Cornicle reticulated: 3.525 .n23ccc. dss -tucstenecepan etc annnsen eases a cea et eerste terse neaenng eee ed ee 10 
2. Cornicle longer than 1.5 times III especially in aptera (p. 314)........--.....:---00-20- macrosiphum 
-. Cornicle not distinctly longer than 1.5 timres TUT 222s earn ee ee 3 
3._ -Hind tarsal Il shorter: than: base) of. V Uic2o2cc ecco cress ccc nee 4 
... Hind tarsal IT not distinctly shorter than base of: Vile seccssccccecnceeeesn nce ense tec ee 7 
4. Unguis longer than) III; rostral TV—--V 0 Gp S21) eee aac rcc creer rece et nn ee ee purshiae 
Unguis as above?-rostral TV --V .15 (p23) 324 )incccesceccncesccer csce roster asncteroces teceneeese se eee sibiricum 
.. Unguis not: longer than TU Bano... cise seencgectheennsictcenaeshe tonuununsseanenspebsnskiiedtyenasarsgnasasaen ee 5 
5. Rostral IV-++V longer than hind tarsal II; lateral hairs on cauda 
7-OF more pains (xi, SOV) hc hee ccc eee cates cee ee crenicornum 
Rostral IV++V not longer than hind tarsal II; lateral hairs on cauda 
Fewer than 7) Pairs i ciesc. cs ccnccasacecsemerennseespcasinees gest osevecseonaona tensed eetentetaeanstusemnnanecsne tee ayia 6 
6. Cornicle shorter than 5 times hind, tarsal) ED. (pi 330) cect ceccceeecercceccet nen esecceeseseeeeeeeeeeeens wasintae 
= Cornicle longer than 5 times hind tarsal TD (p. 320) 2cccesscecccs-ccecesec cece eeoceneressee eee pisi 
7. Unguis longer than 5 times: base Of iV Voc. .nccc coco tecscei cs cncecec chs cases ee aceeet epee sone eee eee 8 
Unguis not longer than 5 times base of VI; sensoria 18 or more on III 
of alata; rostral I[V--V notihatry (p.2302) 22 res dirhodum 
... Unguis as above; sensoria on III of alata fewer than 18; rostrum hairy (p. 295).......... barri 
8. Cornicle shorter than 6 times length of rostral DV V <.2cc-.-ccct-p2cce-ascsccuscass-rancudebgnteqnsnteeuneneueneees 9 
...Cornicle longer than 6 times length of rostral IV+V (p. 324) ......2...2:.--:csecccneceeeeseees sibiricum 
9. Uneguis'1°25-1.6 times length’ of (EET (ps3 19) esccprccecccee eece erect eae pelargonii 
=. “Unguis’.80-1/16 times! length of TEI piv 333 sc ccccceccsece teres ere ec sesscs cetera .zerozalphum 
10. Cornicle with not more than about 4 rows of reticulations...................::::cs:ccccseseceeeeeeeeennpeceennee 11 
-z Cornicle with more than 4 rows: of retictilatiOms.e.ccccccceec cc ceaccennsestscasasecsoceed ee 13 
11. Rostrum with needlelike tip; unguis shorter than cornicle (p. 332)................-.----- zerohypsi* 
Rostrum ending in needlelike point; unguis shorter than twice length 
of cornicle- (pi. 293.) cose eestor enn Ie RE ge eee artemisiphilum* 
Rostrum with needlelike tip; unguis coequal with twice length 
of cornicle (pi S06) cc. ssscccec le ckapeccce cee cece te ee reteset nce ree ncn aa ena oe eee flavilum* 
sean. ROStrum ODtuse 22... ccccs cece yeosercedecec code pu egaducnsentetassceacsapeaasemsees seus aeee ane ee a 12 
12,5), Unguis length) about: times cornicle:(p. 318) essere ese eee niwanistum 
Unguis 1.3-1.4 times cornicle® (py 324) e<icccgeteede ets ee eee sibiricum 
Unguis length not, longerithan’ cornicie: (p.1542)\ eee eee Myzus porosus 
13.. Rostrum acute, may end in needlelike potrts co occc cep cecesccuesesdeesnencecee esceonpecantt- ee 14 
wow! PROSEE UMN OD CUS Sos oes 252s ccs te akan eee ado cen enc ded eed aa lane) 21 
14° Gornicle longer thant lV 2.225.203 2. JO eee a ee 15 
Cornicle not :longer thanyLV 2st. see 5 ee ansansijlieeit ae 16 
15. Unguis longer than cornicle; cornicle not shorter than .55 (p. 300)............-...ss-sccee-+- coweni* 
Unguis. as above: cornicle shorter: thar (5.55. cccc.ccestcanee-oncs dec peunsingeettieces: ne erense ee 15a 
Unguis not longer than cornicle; cornicle .43-.50 (p. 292)........-..-:cc-sccesceeeceeeceeeeeeeee anomellum* 
Unguis ad above: cornicte .47-.59 (p. 297 } vecsutcnsdeeeeesseateeece eee cefsmithi* 
——.  Unguis as above’; cornicle 160-.80'( i, 1305) 20 ee filifoliae* 
15a4LIT shorter:than.60(p.332) 50. ee ee eee ee eee zerothermum* 
TEL 57=.69:' (pe297 i ete Se a ae hee Riehl yey ee ae sae) cefsmithi* 
EET .62-.66 (pi 290) scsvccstiinssgeanisenn-raectereuanaibcncnetec dase Wien a oak rao see a a EE albicornum* 
