Monarch Monitoring Project - 10/15/08

Well it's been another exciting week at the Monarch Monitoring Project! We have had high numbers on our daily census, bringing us to an average of 48.15 monarchs/hour! It was indeed a good week to see monarchs. Unfortunately this past week also brought some sadness to the monarch crew. Dick Walton and Patsy Eickelberg, the director of our project and one of our most wonderful volunteers (respectively), returned to Massachusettes after three fabulous weeks in Cape May. They will be missed greatly!!! Thankfully, Dick and Patsy didn't take all the monarchs with them when they left. Yesterday and today brought in some higher numbers, and we hope that this will continue throughout the week.

Today I would like to blog about monarch predators (and parasites)! Sure, monarchs are unattractive to some potential predators. The milkweed they consume as caterpillars makes them poisonous to most vertebrates (birds, bats, etc). Still, life isn't easy if you are a monarch. In this blog I will attempt to show you that:

It's not (always) easy being orange and black

Imagine that you are a monarch. You can glide lazily around Cape May in broad daylight. Birds don't want to eat you (you taste terrible), and you advertise this fact every second of every day with your magnificent orange and black coloration. Life is good. Or is it? You see a beautiful butterfly bush (Buddleja sp.) just dripping with delicious nectar. You head over and perch on a flower, ready to feast. Suddenly, without warning, something snatches you in its treacherous grasp! Oh no!! It's a praying mantid!! You are gobbled up with no hope of reaching Mexico.

Photo by Michael O'Brien

Aside from the rapacious grasp of mantids, monarchs have other predators to worry about too. Say instead of making it to that butterfly bush, you got tangled in a web along the way. Oh no! Out comes an orb weaver spider, and you are soon again lunch.


It's not just the monarch adults that have all the trouble either. Parasitic insects like the tachinid fly and certain types of wasps, lay their eggs on the monarch caterpillar. The caterpillar is helpless if a parasitic wasp selects it as a host (see below...poor guy).




The tachinid fly is a common monarch parasite. The fly will lay it's eggs on the monarch caterpillars and once they hatch the larvae will burrow inside the monarch. The fly larvae will feed off its host until it is ready to pupate. It will then emerge from the late instar caterpillar or the chrysalis killing the monarch and leaving a string-like structure in it's path. The tachinid will then pupate after emerging from the monarch. Below is a picture of a chrysalis that has been parasitized by a tachinid fly.


The last predator/parasite I wanted to mention is Ophryocystis elektroscirrha also known as OE. OE is a protozoa that parasitizes monarchs and it is very contagious. The female monarch passes it to her offspring directly, but it can also be spread from monarch to monarch interaction. OE causes many problems in monarchs, including a shorter life span, trouble emerging from the chrysalis, and difficulty flying. Luckily we don't have many OE cases in our east coast population, but we have come across a few this fall. Below is a photo of a monarch with OE, the spores are visible on the abdomen:


So as you can see, it's not easy being a monarch. Aside from a long arduous journey to Mexico, monarchs have lots of predators and parasites to deal with. Enough of them make it though, and enough monarchs are able to pass their genes on to the next generation. If anything, this should just remind us how amazing monarchs are. So I tip my hat to you Mr./Ms. Monarch, and wish you the best of luck!