Source, in full
The first quote was made to Stravinsky after he had shown Strauss some of his works in Paris, 1914. The second quote an overheard joke of Strauss later reported to Stravinsky. Found in Kurt Wilhelm, Richard Strauss - an intimate portrait. Thames and Hudson, London, 1898. (Translated from original 1984 German edition by Mary Whittard), page 142.