Caterpillar Update 6/27/17

June 27, 2017 Caterpillar Update

It’s a beautiful thing! Gypsy moth caterpillars have been dying by the thousands all over Rhode Island! We can thank a fungal pathogen, Entomophaga maimaiga, and a wet spring. Gypsy moth caterpillars started dying from Entomophaga mid-May. More died each week until the grand finale which occurred around June 23rd. It was getting a little scary – it looked like we had too many caterpillars in mid-June. Then, thankfully, we received 5 wet days June 16-20. It takes about 7 days for a gypsy moth caterpillar to die once it gets infected by the fungus; so 7 days after June 16 we started seeing massive numbers of gypsy moth caterpillars dying.
Entomophaga dead caterpillars 6.23.17
Entomophaga Maimaiga – killed gypsy moths
Entomophaga dead gm 6.26.17
Gypsy moth killed by Entomophaga maimaiga.

Some caterpillars have pupated. Some pupae may still die of Entomophaga if the caterpillars were infected before pupating. I’m hoping that most of the surviving pupae will emerge as male gypsy moths. Male gypsy moth caterpillars tend to pupate earlier than female gypsy moth caterpillars because the males molt 4 times and the females grow larger and molt 5 times. Since females take longer to mature, most females were still caterpillars when the wet weather started June 16th. Remember – male gypsy moths are dull brown and can fly. Female gypsy moths are white with dark markings and don’t fly.

gypsy moth pupae
Gypsy moth pupae.


male and female gypsy moths 2016
Male and female gypsy moths from 2016.

Forest tent caterpillars defoliated many acres of RI forests in 2017. This native insect is also attacked by different fungal pathogens, but, sadly, these pathogens did not cause the forest tent caterpillar population to crash. Forest tent caterpillar moths started emerging this week and will soon be laying egg masses to overwinter and hatch next spring.

forest tent caterpillar pupa wrapped in leaf
Forest tent caterpillar cocoon wrapped in leaf.


forest tent pupae unwrapped

Forest tent caterpillar cocoon leaf unwrapped.


forest tent caterpillar adult moth
Forest tent caterpillar moth on window screen.


forest tent egg mass
Forest tent caterpillar egg masses will be deposited over the next few weeks.