1910] Wheeler—North American Forms of Lasius umbratus 237 
with grass and is more or less exposed to the sun. The subspecies 
subumbratus is an exclusively boreal form, occurring only in Brit- 
ish America and at elevations above 7,500 ft. in the Rocky 
Mountains. The same is probably true of vestitus. The sub- 
species minutus and speculiventris and the variety aphidicola occur 
in the transition zone and of these only aphidicola is at all common. 
Like our other yellow Lasii, wmbratus is subterranean in its habits 
and devotes itself to the care of root-aphids and -coccids, all or 
nearly all of its food consisting of the sweet excreta of these 
insects. 
The sexual phases are rarely found in the nests of wmbratus, 
apparently because they are not retained by the parental colonies 
for days or weeks during the latter part of the summer or early 
fall but escape for their marriage flight very soon after reaching 
maturity. Recent studies in Europe indicate that the just- 
fertilized wmbratus queen is unable to establish her colony inde- 
pendently after the manner of L. niger and flavus, but becomes a 
temporary parasite on a colony of niger or of one of its subspecies 
or varieties after the manner of certain species of Formica of the 
rufa and exsecta groups. Our American umbratus forms apparently 
behave in the same manner. De Lannoy and Wasmann, moreover, 
have collected some evidence to show that wmbratus is in turn the 
temporary host of the palearctic L. fuliginosus. The rare or 
sporadic occurrence of wmbratus on both continents certainly 
points to parasitic habits on the part of the queen and her incip- 
ient colony. 
The following tables will facilitate the identification of workers 
and females of our North American forms of wmbratus: 
WORKERS. 
1. Antennal scapes and tibize with very few or no erect hairs; gaster 
With appressed pubeESGeNCe a paey. ns cles ovenwe at Reto case) es otecele 6 fieiaiehe ie: faa s g 
Antennal scapes and tibize with abundant erect hairs; gaster with- 
Out pubescenceMer es ace stole: wae ee subsp. speculiventris Emery. 
2. Gaster with sparse pubescence and short erect hairs, shining; aver- 
agelength ofbodyiomer4immy enters. th tee. le ome. ate ae ete ats 3 
Gaster very densely pubescent, with long erect hairs, subopaque; 
average length of body less than4mm............ subsp. minutus Emery. 
3 Paletyellows eyes!smalleeome ste. socee ieee subsp. subumbratus Viereck. 
Brownish yellow; eyes larger....subsp. mixtus Nyl. var. aphidicola Walsh. 
