19 ^ 2 ] Notes on Nesting Habits of North American Bumblebees 201 
Friese, H. und Wagner, F. V. 1910. Zoologische Studien an 
Hummeln. Zool. Jahrb., Abt. Syst., Vol. 29, pp. 1-104, 
pis. 1-7. 
Frison, T. II. 1916. Note on the Habits of Psithyrus variabilis 
Cresson. Bull. Brookl. Ent. Soc., Vol. 11, pp. 46-47. 
1917. Notes on Bombidse, and on the Life History of 
Bombus auricomus Robt. Ann. Ent. Soc. Amer., Vol. 10, 
pp. 277-286, pis. 23, 24. 
1918. Additional Notes on the Life History of Bombus 
auricomus Robt. Ann. Ent. Soc. Amer., Vol. 11, pp. 43- 
48, pi. 3. 
1921. Psithyrus laboriosus Fabr. in the Nests of Bumble- 
bees (Hym.). Canad. Ent., Vol. 53, pp. 100-101. 
1921a. New Distribution Records for North American 
Bremidse, with the Description of a New Species (Hym.). 
Ent. News, Vol. 32. pp. 144-149. 
Harter, R. 1890. Biologische Beobachtungen an Hummeln. 
27. Bericht Oberhess. Gesellsch. Natur- u. Heilkunde, pp. 
59-75. 
H offer, E. 1881. Beschreibung eines instructiven Nestes von 
Bombus confusus Schenck. Mitth. Naturw. Ver. Steier- 
mark, Vol. 18, pp. 93-106, 1 pi. 
1882/83. Die Hummeln Steiennarks. Lebensgeschichte 
und Beschreibung derselben. Leuschner & Lubenslcy, 
Graz. 
1885. Ein sehr lehrreiches Nest des Bombus terrestris L. 
Wien. Ent. Zeit., Vol. 4. pp. 84-90. 
1888. Die Schmarotzerhummeln Steiennarks. Lebens- 
geschichte und Beschreibung derselben. Mitth. Naturw. 
Ver. Steiermark, Vol. 25, pp. 82-159, 1 pi. 
Howard, L. 0. 1918. An Unusual Bumblebees’ Nest (Hym.). 
Ent. News, Vol. 29, pp. 114-115. 
Hudson, W. II. 1892. Humble-Bees and Other Matters. 
The Naturalist in La Plata. Chapman & Hall, London, 
pp. 154-161. 
