Fig. 4.--Calf in untreated north part of H-shaped barn mentioned under 
fig. 3. House flies were numerous on calf and about pen. 
Fig. 5.--Calf in south part of H-shaped barn mentioned under fig. 3. 
Although house flies had free access from untreated north part, on this calf they 
were only about one-tenth as numerous as on calf pictured in fig. 4. 
