Strikes me as odd based on my own experience. Back in 1965 I was a navy wife living in Puerto Rico. There was a day when my husband and I teamed up with another couple to walk the trails to the top of El Yunque. As luck would have it we got lost on the trail and made it to the top of Mt Britain (the next one over) instead. It was all part of the rain forest that was a national park with trails all through it.
One of the things that struck me as unusual was the lack of insects and critters that we encountered on our trek. Trust me, I was watching closely for any sort of crawly or flying things. '65 was quite a bit before the time frame that the article is about and there were already a limited number of the things that one would expect to find in a rain forest.
Since we lived in another part of PR we were well aware of lots of insects that came with the place. In fact most everybody allowed lizards to climb up and down their walls because they ate the bugs.