1948] 
Bailey — Tab anus atratus 
133 
placed in the mass. Cameron (1926) states that the 
darkening process takes about six hours for Chrysops 
eggs, which become jet black. He notes that the pigmen- 
tation develops much more rapidly in full sunlight than in 
the laboratory. 
The egg mass of T. atratus Fabricius has been described 
in detail by Hart (1895), and Schwardt (1936) provided 
photographs which agree closely with Hart’s description. 
Schwardt also states “T. atratus deposits its eggs in 
masses which are so constant in structural plan as to make 
specific determination of the egg mass readily possible.” 
Fig. 1. Egg masses of Tabanus atratus nantucTcensis. Photograph by 
Arthur F. Dewsnap, Jr. (About 4x natural size) 
This is especially noteworthy since the egg masses of the 
subspecies nantuckensis are strikingly different (see 
Figure 1). In the words of Hart (1895), atratus egg 
masses are “ subconic, with oval base, 10-15 mm. long 
and 8-10 mm. wide, height 5-7 mm. ; sides convex or con- 
cave, apex correspondingly rounded or pointed. . . . The 
eggs are stacked in four or five tiers, one above another, 
and gummed together in a firm mass.” This is the type 
very rarely found on the saltmarsh where the usual form 
of the egg mass closely resembles the basal one in the 
accompanying figure. 
The measurements given by Hart (1895) and by Stone 
(1930) suggest a maximum of 2 : 1 for the length to width 
ratio of T. atratus egg masses whereas those of the sub- 
