Study sites
Damselflies were captured at two stream locations in Emmett County, Michigan throughout the month of July, 2016. The sites two sites were the Maple River (45.528412, -84.774698), and the O’Neal River (45.712491, -84.904707). Both stream sites were located in relatively isolated areas and hosted dense populations of C. maculata.

Stream characteristics
A measuring tape was used to take three measurements of stream width at three points along the collection site, which spanned a 50m range along the stream. The width was taken from where the water met the river bank on either side of the river. Depth measurements were taken at the midpoint of each width measurement, from the surface of the water to the riverbed. To measure stream flow, a 10-meter stretch was first measured and marked along the sampling location. A tennis ball was released at one end and the time it took to flow to the other end of the 10-meters was measured using a stopwatch. This was process was repeated three times.

Collection and age standardization
Larvae were caught using dip nets and stored in small vials with stream water, while adults were caught with insect nets and kept in glasseine envelopes. Only reproductively active adults were captured to lower the variability of the age of the specimen caught. For males, reproductively active adults were determined by display of territorial behavior on the river, meaning that they were defending territory for oviposition (Córdoba-Aguilar, 2002; Siva-Jothy, 1999). For females, only adults that were within two feet of the stream were collected. This selective collection aimed to avoid teneral adults, and adults who are too old to reproduce or defend territory.

Measurement and Dissection
Prior to assessing specimen for parasites, imagines and larvae were kept chilled in a cooler in the field. Once ready for processing, specimens were removed from storage and measured. The wet weight was determined by measuring the specimen in a glasseine envelope, and upon removing the damselfly, reweighing the empty glasseine envelope. Sex was noted for adults, and is easily identified by white spot on the tip of the female wing. The length of the right and left hind wings, and the abdomen were measured using the software ImageJ. Pictures of each specimen were taken immediately prior to dissection next to a ruler for scale, and the average of 3 measurements were used for data analysis. Wing length was measured from the nodus to the furthest edge of the hindwing, and the abdomen measurements were taken from the point at which the abdomen and thorax meet, to the end of the final abdominal segment. The fluctuating asymmetry was calculated by taking the absolute difference of the average left and right hindwing measurements. Fluctuating asymmetry of wings and abdomen measurements were indicators of fitness for our study given that males with more symmetrical wings and larger size have been shown to have higher lifetime mating success (Harvey and Walsh 1993) and that many studies have found a similarly increased lifetime mating success rate for larger damselflies (Sokolovska, Rowe, and Johansson 2000).
To examine gut contents, the abdomen was opened using small scissors and the intestine was removed onto a microscope slide. With the addition of a small amount of deionized water, the gut was gently flattened to release gut contents. Gregarines were counted for each specimen. For larvae, the head was removed and gut was gently pulled out onto a slide for examination. Gregarines were found in the midgut, and could be seen through the gut wall if present. Occasionally, gametocysts were found in the fecal pellets in the cups, and in one case, several trophozites were found to be passed through. There was no indication that specimen infected by gregarines were in any way unhealthy.

Adult Survivorship Study
To assess potential impacts of gregarines on survival, the process outlined by Hecker et. al (2002) was used. Reproductively mature adults were kept in individual plastic cups with 3 mL of water and a stick on which they could perch. These conditions simulate food-stressed conditions. Cups were kept covered and kept at room temperature. Individuals were checked every 12 hours to see if any had died, or were moribund. ‘Moribund’ was classified by showing little response when lightly touched. If they were deemed dead or moribund, specimen were first photographed, and then were dissected for parasites, and their hours survived were noted, starting from the time that specimen were inserted into cups.