How to custom the tick and type in bwplot

Dear R users

I use bwplot to plot some figures.  There are two troubles:

1. How to change the dot of the mean to a line, like the style in  
boxplot

Sometimes you need to refer the the help page for panel.<type of  
plot>, in this case:
?panel.bwplot

... so the answer is now staring you in the face:
bwplot(decrease ~ treatment, OrchardSprays, groups = rowpos, pch="|")

2. How to hide some tick marks.  For example, I have seven tick: A,  
B, C, D,
E, F, G,
   but I want show four marks: A, C, E, G on the x-axis.

Using the example in bwplot again, and a fair amount of fruitless  
experimentation with the theory that one could do anything useful with  
scales=list(at= list(<something>)), I finally ended up trying ,  
labels=c( ) per Sarkar's Lattice book, producing this:

bwplot(decrease ~ treatment, OrchardSprays, groups = rowpos,  
scales=list(x=list( labels=c("A","","","D","","F","","") )))

David Winsemius, MD
Heritage Laboratories
West Hartford, CT