The density of corn pollen on leaves of milkweed plants inside and outside of cornfields was measured in several studies from different localities. The purpose was to obtain a representative picture of naturally occurring pollen densities to provide a perspective for laboratory and field studies of monarch larvae feeding on milkweed leaves with Bt corn pollen. Pollen density was highest (average 170.6 grains per cm ² ) inside the cornfield and was progressively lower from the field edge outward, falling to 14.2 grains per cm ² at 2 m. Inside the cornfield, and for each distance from the field edge, a frequency distribution is presented showing the proportion of leaf samples with different pollen densities. Inside cornfields, 95% of leaf samples had pollen densities below 600 grains per cm ² and the highest pollen density observed was 1400 grains per cm ² , which occurred in a study with a rainless anthesis period. All other studies had rainfall events during the anthesis period. A single rain event can remove 54–86% of the pollen on leaves. Leaves on the upper portion of milkweed plants, where young monarch larvae tend to feed, had only 30–50% of the pollen density levels of middle leaves.

To assess the change in the size of the eastern North American monarch butterfly summer population, studies have used long-term data sets of counts of adult butterflies or eggs per milkweed stem. Despite the observed decline in the monarch population as measured at overwintering sites in Mexico, these studies found no decline in summer counts in the Midwest, the core of the summer breeding range, leading to a suggestion that the cause of the monarch population decline is not the loss of Midwest agricultural milkweeds but increased mortality during the fall migration. Using these counts to estimate population size, however, does not account for the shift of monarch activity from agricultural fields to non-agricultural sites over the past 20 years, as a result of the loss of agricultural milkweeds due to the near-ubiquitous use of glyphosate herbicides. We present the counter-hypotheses that the proportion of the monarch population present in non-agricultural habitats, where counts are made, has increased and that counts reflect both population size and the proportion of the population observed. We use data on the historical change in the proportion of milkweeds, and thus monarch activity, in agricultural fields and non-agricultural habitats to show why using counts can produce misleading conclusions about population size. We then separate out the shifting proportion effect from the counts to estimate the population size and show that these corrected summer monarch counts show a decline over time and are correlated with the size of the overwintering population. In addition, we present evidence against the hypothesis of increased mortality during migration. The milkweed limitation hypothesis for monarch decline remains supported and conservation efforts focusing on adding milkweeds to the landscape in the summer breeding region have a sound scientific basis.

Ries et al. used surveys of adult butterflies made during July 19 to August 15 by NABA (North American Butterfly Association) and IBMN (Illinois Butterfly Monitoring Network) to estimate end-of-summer population size. The most serious problem with their analysis is with the assumption that the habitats where these surveys were made provide an accurate measure of population size. These counts are made in a variety of nonagricultural habitats. But in the late 1990s, corn and soybean fields accounted for >80% of monarch egg production (Oberhauser et al. 2001). Counts in nonagricultural habitats would reflect the size of the general population of monarchs if the proportion of the population occupying those habitats remained constant over the years. However, over the past decade and a half, milkweeds were virtually eliminated from agricultural fields, resulting in progressively less monarch activity in agricultural fields (Pleasants and Oberhauser 2013) and proportionately more in nonagricultural areas. Therefore, yearly butterfly counts in nonagricultural areas would progressively overestimate the actual size of the population. In fact, if the population remained constant, as Ries et al. (2015) argue, we would have actually expected to see an increase in butterfly counts over the years because of the increasing proportion of the population occupying nonagricultural habitats. Ries et al. found no such increase, which we argue indicates that the overall population was in fact declining.

As online courses become increasingly common at the college level, an ongoing concern is how to ensure academic integrity in the online environment. One area that has received particular attention is that of preventing cheating during unproctored online exams. In this study, we examine students’ behavior during unproctored exams taken in an online introductory biology course. A feature of the learning management platform used for the course gave us the ability to detect cheating behavior involving students leaving the test page and viewing other material on their computers. This allowed us to determine what proportion of students cheated and examine the efficacy of various measures to mitigate cheating. We also explored the relationship between cheating behavior and exam performance. We found that 70% of students were observed cheating, and most of those who cheated did so on the majority of test questions. Appealing to students’ honesty or requiring them to pledge their honesty were found to be ineffective at curbing cheating. However, when students received a warning that we had technology that could detect cheating, coupled with threats of harsh penalties, cheating behavior dropped to 15% of students. Unexpectedly, we did not find evidence that students’ exam performance changed when their cheating behavior changed, indicating that this common form of cheating might not be as effective as students, or their instructors believe it to be.