“What are these worms gathering underneath my son’s mattress?” asks this mother from Melbourne Australia. Her question pertains to the minuscule, black worms with white polka dots in the photos below.

Now, as these photos are not very zoomed in, it is difficult to make out any of the creatures’ finer details, besides their coloration and white spots. In addition to this, our reader does not provide more context than what is written above, so we have nothing else to base an identification on. That said, we do believe these to be lily caterpillars. Lily caterpillars are the larval form of the lily moth, which are native to Australia, and are very common along the eastern coast, which makes sense for Melbourne. These critters are considered pests — not household ones, but garden ones. They only purposefully infest plants, not mattresses or any other textiles. With that in mind, why do we think these are lily caterpillars? Mostly because of the big white spots, which are not as common as the smaller, white speckles of other species of caterpillar, as well as the fact that they are common in this part of Australia. This begs the question of why these caterpillars were found here, seeing as they have no reason to be infesting our reader’s son’s mattress.

There are a few possibilities that could explain how these caterpillars ended up here. Firstly, the mother moth may have flown into our reader’s home while pregnant, and laid her eggs near or on the mattress because she thought it a safe place to store her eggs. Secondly, the same scenario may apply, except that the mother moth laid her eggs here because she was trapped inside the home and could not make it outside to lay her eggs. Thirdly, our reader’s son may have carried in a patch of eggs on his clothing from the outdoor, and then they hatched on his mattress, which consequently spawned the infestation.

Either way, what we recommend our reader do is thoroughly clean the mattress and the area around, laundering any textiles that can be laundered, and vacuuming the room for any unhatched eggs. When it comes to the caterpillars, we recommend that she take them outside and leave them somewhere where there are trees or shrubs (something with leaves for them to feed on). She will also want to check the rest of her home for any more roaming caterpillars and take those outside as well. If our reader finds that the infestation is getting out of hand, and that the caterpillars are causing damage to items in her home, then these might be something else. In that case, our reader has a couple of options. She can: 1) Take pictures that are more zoomed in, and of a good resolution, and send them our way (so we can have another go at identifying the creatures). 2) Bring samples of the worms to her local county extension office so that the agricultural department can have a look and give a second opinion. 3) Call pest control to eliminate the infestation.

In conclusion, it is our opinion that the creatures found underneath our reader’s son’s mattress are lily caterpillars. These caterpillars are not harmful, and do not infest homes on purpose (especially mattresses), as there is nothing there for them to eat. We understand that it is still not pleasant to find such creatures in one’s home, so we hope that the advice listed above is useful. We wish our reader and her son the best!

• 
•