Re: why are ladybugs called ladybugs?

The name comes from the notion that these beetles are somehow dedicated to 
the Virgin Mary, as in Our Lady's beetles (or "bugs").  They are called by 
similar names in many European countries, such as Nyckelpiga (Our Lady's 
Key-Maid) in Scandinavia, Jungfrau Marias Gullhona (the Virgin Mary's 
golden hen) and Marien-käfer (Mary's beetles) in Germany and Betes de la 
Vierge (animals of the Virgin) in France.  In England they were also called 
Lady-bird, or Bishop Barnabee. In Scotland they were called Lady Lanners, 
Dr. Ellison or King Calowa, usually associated with a rhyme such as 

           King, King Calowa
           Up your wings and flee awa'
           Over land, and over sea 
           Tell me where my love can be

For some reason the name ladybug (or more accurately ladybird beetle) stuck 
and that is what we call these useful insects today.

References:

Berenbaum, M. R. 1993. Ninety-nine more maggots, mites, and munchers. Univ. 
of Illinois Press, Urbana.

Cowan, F. 1865. Currious history of insects; including spiders and 
scorpions.  J. B. Lippencott, Philadelphia.