Monarch butterflies play a vital role as pollinators in the ecosystem, but they are quickly and exponentially decreasing in numbers regarding their population over the past decade. As a result, a problem that has always existed for monarchs, the parasite Ophryocystis elektroscirrha (OE) in monarch bloodlines, has now become a more significant issue. OE spores have evolved to exist and

grow within monarch larvae, persisting through even the milkweed toxins in the caterpillar's gut; however, they are affected by the level of that toxicity (De Roode).

In this experiment I studied the effects of two different milkweed species, Asclepias curassavica and Asclepias fascicularis, on the OE spores ability to multiply and cause harm in monarch butterflies. I exposed 20 monarchs to OE spores as young larvae, leaving 10 for the control group, which ingested no spores. Both control and experimental groups were split into two equally numbered groups: half of them consumed only narrow leaf milkweed (A. fascicularis) and half consumed only tropical milkweed (A. curassavica). With the pre-knowledge that narrow leaf milkweed is more toxic than tropical milkweed (De Roode), I tested to see if the infected caterpillars eating A. fascicularis would be healthier than the infected caterpillars eating A. curassavica, with fewer deformities, larger size, smaller adult spore concentrations.

I found that the infected caterpillars had larger pupa lengths when they consumed tropical milkweed, and that infected caterpillars eating tropical milkweed had larger pupa size than their corresponding control. This suggests that the wingspan of monarchs with OE increases when they eat tropical milkweed. However, due to limitations caused by the season, the experimental monarchs have not all emerged as adults and I am unable to finish collecting results. More trials will be performed to prove that the toxins in milkweed either positively, negatively, or neutrally impact infected monarchs.