“What are these tiny worm-like creatures? We get quite a few and have had 2 groups this morning” writes this reader about the horde of larvae-like organisms pictured below. The cola-colored “worm-like” creature was allegedly “deposited/dropped by something onto” our reader’s “tile patio outside”.
Additionally, our reader (who resides in a rainforest of the mountainous regions of Costa Rica) states that the “whole group” “moves as one,” and if they start to get too close to her home, then she will place a leaf in front of the cluster. Then, she waits “for them to climb aboard” before she moves them back to the grass. She also mentions that during certain times of the year, she experiences large numbers of moths “both large and small” when the lights are on in the evenings. “One of our dogs thinks they are a crunchy treat when he catches one.”
Now, when it comes to this mass of larvae, we could not find an exact match in terms of the creatures’ physical appearances, but given the way they travel, we would suppose that these are some species of sawfly larvae. Adult sawflies are wasp-like insects that feed on the leaves of various plants, depending on the species. To clarify, they are not moths, and so are not related to the moths that our reader has been seeing on her property. Meanwhile, the sawfly larvae are caterpillar-like (but not actual caterpillars) critters that travel in large groups, or rather, piles. This is because there is safety in numbers. Alone, any one of these larvae would easily get snatched up by a bird or frog, but together, this mass of writhing larvae can fend off predators by assuming the illusion of one big creature.
Moving on, we cannot say for sure that the sawfly larvae are moving toward our reader’s house because they want to enter it, but if this is the case then the reason for this may be that they are seeking shelter, rather than that they want to infest our reader’s home for the purpose of eating food. While the diet of the sawfly varies from species to species, they generally will feed on various species of trees, so we doubt they would be attracted to any houseplants our reader may have in her home when they are surrounded by trees in the rainforest.
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In conclusion, the worm-like creatures our reader found on her patio are sawfly larvae. We do not know exactly what species, but as there are over 8000 species, it would be difficult to pinpoint the exact one. We think our reader is correct in simply putting the larvae on a leaf and turning them in a different direction, as this is likely the most gentle and humane way of dealing with this issue. We commend her for this and recommend that she continue with this method. Lastly, we hope that this article proves enlightening to our reader, and we wish her the best.