Confusion matrix: splitting the name of classes into two lines

Question

I am trying to create a confusion matrix. The matrix works fine although the class names are too large and thus overflow. I want to split the class names into two lines. The \\ command does not work in this case. How can I split the class names into two lines?

\documentclass{standalone}  
\usepackage{tikz}
\usepackage{ifthen}
\usetikzlibrary{matrix,calc}
\usepackage{xstring} % added to extract the . <<<<<
\begin{document}
{
    %The matrix in numbers
    %Horizontal target class
    %Vertical output class
    \centering
    \def\myConfMat{% divided by 10
        { 
            {573.7,29.0,50.7,4.1,75.3,92.6,6.2},  %row 1
            {394.0,341.1,571.5,16.8,61.8,369.2,82.9},  %row 2
            {11.4,10.5,139.2,.5,15.9,37.7,35.2},  %row 3
            {.8,1.3,23.5,1744.8,132.7,413.8,26.9},  %row 4
            {146.7,3.7,45.6,79.0,946.6,1929.8,31.2},  %row 5
            {83.7,58.4 ,281.7,542.9,889.1,3691.6,173.7},  %row 6
            {17.4,10.9,228.9,95.9,161.7,709.1,203.5},  %row 7
    }}
\def\classNames{{&quot;Apidae&quot;,&quot;Andrenidae&quot;,&quot;Honey\\bee&quot;,&quot;Colletidae&quot;,&quot;Bumble\\bee&quot;,&quot;Buff-tailed&quot;,&quot;Andrena&quot;}} %class names. Adapt at will  

\def\numClasses{7} %number of classes. Could be automatic, but you can change it for tests.

\def\myScale{1.2} % 1.5 is a good scale. Values under 1 may need smaller fonts!
\begin{tikzpicture}[
    scale = \myScale,
    %font={\scriptsize}, %for smaller scales, even \tiny may be useful
    ]

    \tikzset{vertical label/.style={rotate=90,anchor=east}}   % usable styles for below
    \tikzset{diagonal label/.style={rotate=45,anchor=north east}}

    \foreach \y in {1,...,\numClasses} %loop vertical starting on top
    {
        % Add class name on the left
        \node [anchor=east] at (0.4,-\y) {\pgfmathparse{\classNames[\y-1]}\pgfmathresult};          
        \foreach \x in {1,...,\numClasses}  %loop horizontal starting on left
        {
            %---- Start of automatic calculation of totSamples for the column ------------  
            \pgfmathsetmacro{\totSamples}{0}
            \foreach \ll in {1,...,\numClasses}
            {
                  \pgfmathsetmacro{\tmp}{\totSamples+ \myConfMat[\ll-1][\x-1]} %accumulate it with previous
                  \global\let\totSamples\tmp% put the final sum in variable
            }
            %---- End of automatic calculation of totSamples ----------------               
            \begin{scope}[shift={(\x,-\y)}]
                \pgfmathsetmacro{\r}{\myConfMat[\y-1][\x-1]}   %                            
                \pgfmathtruncatemacro{\p}{round(\r/\totSamples*100)}
                \coordinate (C) at (0,0);
                \ifthenelse{\p&lt;50}{\def\txtcol{black}}{\def\txtcol{white}} %decide text color for contrast
                \node[
                draw,                 %draw lines
                text=\txtcol,         %text color (automatic for better contrast)
                align=center,         %align text inside cells (also for wrapping)
                fill=black!\p,        %intensity of fill (can change base color)
                minimum size=\myScale*10mm,    %cell size to fit the scale and integer dimensions (in cm)
                inner sep=0,          %remove all inner gaps to save space in small scales
                ] (C) {\StrSubstitute{\r}{.}{}\\\p\%};     %text to put in cell (adapt at will)
                %Now if last vertical class add its label at the bottom
                \ifthenelse{\y=\numClasses}{
                    \node [] at ($(C)-(0,0.75)$) % can use vertical or diagonal label as option
                    {\pgfmathparse{\classNames[\x-1]}\pgfmathresult};}{}
            \end{scope}
        }
    }
    %Now add x and y labels on suitable coordinates
    \coordinate (yaxis) at (-0.85,0.5-\numClasses/2) ;  %must adapt if class labels are wider!
    \coordinate (xaxis) at (0.5+\numClasses/2, -\numClasses-1.25); %id. for non horizontal labels!
    \node [vertical label] at (yaxis) {Actual Class};
    \node []               at (xaxis) {Predicted Class};
\end{tikzpicture}


\end{document}