title: Selectively apply font style to strip and legend labels in ggplot()
body: <p>I have a facet_wrap()-ed histogram pair that shows two histograms. One of the factor levels is a species binomial that should be in italics, but the other factor level should be in normal text:</p>
  
  <pre><code>library(tidyverse)
  set.seed(1234)
  data1 &lt;- tibble(species = c(rep("H. sapiens",100), rep("Other Species",100)),
              height = c(rnorm(100,174,25),rnorm(100,125,15)))
  plt &lt;- ggplot(data1) +
    geom_histogram(aes(x=height,fill=species),bins=10) +
    facet_wrap(~species,nrow = 2)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/cUY6p.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cUY6p.png" alt="facet_wrap histogram"></a></p>
  
  <p>I tried writing a labeller function:</p>
  
  <pre><code>lbl &lt;- function(variable, value) {
    if(variable == "H. sapiens") value= italics("H. sapiens") else value
  }
  </code></pre>
  
  <p>and using it in the call to facet_wrap:</p>
  
  <pre><code>facet_wrap(~species,nrow = 2, labeller = lbl)
  </code></pre>
  
  <p>but this replaced the previous facet label with the numerals 1 and 2, and produced a warning:</p>
  
  <blockquote>
    <p>Warning: The labeller API has been updated. Labellers taking <code>variable</code>and
     <code>value</code> arguments are now deprecated. See labellers documentation.</p>
  </blockquote>
  
  <p>How can I apply italics only to the strip in which H. sapiens appears, and only to the appropriate label in the legend? I realize these are two separate issues, but they both arise here.</p>
  
  <p>I saw <a href="https://stackoverflow.com/questions/16490331/combining-new-lines-and-italics-in-facet-labels-with-ggplot2">this post</a> but it appears that there are unsolved issues (and it's a more-complicated example and quite confusing). Is there as solution?</p>