Western honey bees (Apis mellifera) face an increasing number of challenges that in recent years have led to significant economic effects on apiculture, with attendant consequences for agriculture. Nosemosis is a fungal infection of honey bees caused by either Nosema apis or N. ceranae. The putative greater virulence of N. ceranae has spurred interest in understanding how it differs from N. apis. Little is known of effects of N. apis or N. ceranae on honey bee learning and memory. Following a Pavlovian model that relies on the proboscis extension reflex, we compared acquisition learning and long-term memory recall of uninfected (control) honey bees versus those inoculated with N. apis, N. ceranae, or both. We also tested whether spore intensity was associated with variation in learning and memory. Neither learning nor memory differed among treatments. There was no evidence of a relationship between spore intensity and learning, and only limited evidence of a negative effect on memory; this occurred only in the co-inoculation treatment. Our results suggest that if Nosema spp. are contributing to unusually high colony losses in recent years, the mechanism by which they may affect honey bees is probably not related to effects on learning or memory, at least as assessed by the proboscis extension reflex.Western honey bees (Apis mellifera) are ecologically and economically important pollinators world-wide, with pollination services contributing billions of dollars annually 1,2 . For reasons that appear multi-causal 3-6 , honey bee colonies have in recent years been suffering significant mortality in regions around the world, likely at an unprecedented rate 7 . Causes of mortality include pesticides, shortages of forage, improper management by beekeepers, and parasites [8][9][10][11][12][13][14][15] . Among the latter are two species of microsporidian fungi, Nosema apis and N. ceranae. Although many signs of pathology have been identified for infections with N. apis and N. ceranae, effects of these parasites on honey bee acquisition learning (hereafter, learning) and long-term memory recall (hereafter, memory) are not well studied. Wright (ref. 16) found that fungal infection by Metarhizium anisopliae was associated with both enhanced and impaired learning in honey bees, depending on a variety of other variables, including infection with Nosema apis. Here, we test directly whether Nosema spp. parasitism affects learning and memory in honey bees.Nosema apis was the historic species infecting A. mellifera honey bees 17 , but probably early in this century, N. ceranae became an invasive parasite of A. mellifera, transferring from Asian honey bees A. cerana [18][19][20][21][22][23] . Currently, N. ceranae essentially matches N. apis's nearly global distribution 22 , and the two species can co-infect honey bees 9,22,24,25 . Some theory predicts that co-infections select for increased virulence because of within-host competition for resources [26][27][28] . Although co-infections occur, N. ceranae has become the predominan...

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is a significant invasive pest in soft-skin fruits and berries in Asia, Europe, and North and South America. Many herbivorous insects use multiple cues for host selection, particularly olfactory and visual stimuli. The visual system of closely-related Drosophila melanogaster is well-documented, expressing strong sensitivity to short-wavelength colors (ultraviolet to green) and only limited sensitivity to long-wavelength colors (red to infrared). Our results suggest that D. suzukii have limited ability to distinguish red consistent with visual sensitivity range within the melanogaster subgroup. We propose that color contrast rather than color appearance may be of greater importance in orientation and attraction. We propose that differences in reflectance between light wavelengths important for color opponency are key to color discrimination to provide color contrast between foreground and background, as occurs between fruit and foliage, during host-finding.