232 
Psyche 
[Vol. 89 
Table 6. Mean fresh weights (mg) of adults and larvae of three species of Osmia. 
Weights for O. montana and californica are for two-year forms, those for O. iridis for 
one-year forms. N = sample size, ESR = expected sex ratio (SI 9)- 
Adults 
larvae 
% wgt. 
loss 
(5 
$ 
<5 
9 
(5 
9 
montana 
live wgt 
71.9 
125.3 
93.1 
161.7 
23.0 
22.6 
± SD 
16.1 
16.9 
19.2 
20.3 
3.0 
2.1 
N 
21 
34 
21 
34 
21 
34 
ESR 
1.74 
1.74 
californica 
live wgt 
73.3 
121.2 
94.1 
156.6 
22.0 
22.8 
± SD 
14.5 
19.7 
18.6 
21.8 
4.3 
3.5 
N 
23 
16 
23 
16 
23 
16 
ESR 
1.65 
1.66 
iridis 
live wgt 
38.3 
66.7 
± SD 
4.9 
9.5 
N 
58 
15 
ESR 
1.74 
no consistent tendency for observed sex ratios to move towards 
the equilibrium sex ratio in 1980 for either O. montana or O. eali- 
fornica (Fig. 1). 
Discussion 
The data presented above are noteworthy for several reasons. 
First, these three species provide the best documented examples of 
parsivoltine emergence patterns in bees. Indeed, among Hymenop- 
tera, detailed examples of parsivoltinism are available only for 
diprionid sawflies (Prebble 1941, Griffiths 1959, Sullivan and Wal- 
lace 1967, Wallace and Sullivan 1974). Previous reports of such 
emergence patterns in bees have been based on small sample sizes 
( Dianthidium pudicum consimile (Ashmead) (Davidson 1896), Me- 
lissodes robust ior Cockerell (MacSwain 1958), Proche/ostoma phil- 
adelphi (Robertson) (Krombein 1967), Perdita nuda Cockerell, 
Sphecodes sp. (Torchio 1975), Osmia marginipennis Cresson (Park- 
er 1980), and Hopiitis biscute/lae (Cockerell) (Rust 1980) ). 
