LitCharts assigns a color and icon to each theme in The 5th Wave, which you can use to track the themes throughout the work.
Trust and Belief
Survival and Perseverance
Warfare and Dehumanization
Family
Summary
Analysis
The next day at the refugee camp, another drone came back. Crisco tried to gift Cassie a diamond necklace, but she told him to be quiet to avoid attracting the drones—plus, she didn’t like him grave robbing. Hutchfield figured the drones must be only for recon purposes, since they hadn’t attacked. Cassie’s dad pointed out that comparatively primitive human satellites could do the same thing—he thought the drones had nothing to do with humans and were just measuring the atmosphere in preparation for the Others to live on Earth themselves.
At one time, a diamond necklace would have been a valuable gift, but the apocalypse has made many things people used to value worthless. Although Cassie’s dad perhaps underestimates the ruthlessness of the aliens, he is also one of the few to view things from a wider perspective. He realizes that, as much as the aliens are focusing on destroying humanity, ultimately the aliens are most interested in furthering their own goals.