Identification of the pan-allergen tropomyosin from the common bed bug (Cimex lectularius).

Tropomyosin is a muscle contraction protein documented across all animal life. Despite its ubiquity, its unique structure in invertebrates leads to allergic responses in humans that vertebrate tropomyosin does not. High degrees of homology can explain cross-reactivity between tropomyosin derived from distantly-related arthropod species and establishes tropomyosin as a panallergen. Given this cross-reactivity and that they are commonly found in high numbers indoors, research on the potential of the common bed bug (Cimex lectularius L.) to contribute tropomyosin to the indoor environment is needed. Therefore, we investigated tropomyosin homology between bed bugs and known tropomyosin allergens from other taxa, tropomyosin in bed bug bodies, feces, and exuviae (cast skins), tropomyosin persistence over time, and impacts of common bed bug treatment strategies on detectable tropomyosin. Tropomyosin was detected in mechanically fractured bed bug cadavers and was detectable in bed bugs cadavers aged for 18 months. Additionally, a survey of pest management professionals showed dead bed bugs are not cleaned up following treatment. As such, dead bed bugs could act as tropomyosin reservoirs following bed bug treatment and exposure to tropomyosin from bed bugs could sensitize individuals and lead to increased responses to other arthropod tropomyosin.

Spatial distribution of histamine in bed bug-infested homes.

Histamine is a component of the bed bug aggregation pheromone. It was recently identified as an environmental contaminant in homes with active bed bug infestations, posing a potential health risk to humans via skin contact or inhalation. It remains unclear how histamine is distributed in homes and if histamine can become airborne. In the present study, histamine levels in household dust were quantified from multiple locations within bed bug infested and uninfested apartments. Bed bug population levels were quantified using both traps and visual counts. The amount of histamine detected varied significantly with respect to sampling location, with the highest concentration of histamine quantified from bedding material. Infestation severity did not have a significant effect on histamine quantified at any location. Our results indicate that the bedroom should be the primary focus of histamine mitigation efforts, although histamine can be found throughout the home. Histamine quantified from homes without active bed bug infestations suggests that histamine from previous infestations can persist following pest eradication. These findings highlight the importance of histamine as a potential insect allergen and will be important for the development of targeted mitigation strategies of bed bug histamine.

Exuviae Recycling Can Enhance Queen Oviposition and Colony Growth in Subterranean Termites (Blattodea: Rhinotermitidae: Coptotermes).

Wood-feeding termites have a nitrogen-poor diet and have therefore evolved nitrogen conservation strategies. However, termite workers molt periodically, and throughout the lifetime of a colony, millions of exuviae, a nitrogen-rich resource, are produced by the colony. In Coptotermes Wasmann, workers foraging at remote feeding sites must return to the central part of the nest to molt, where the queen, king, eggs, and larvae are located. It was hypothesized that this molting-site fidelity is an efficient way to recycle nitrogen for reproduction and colony growth, as nestmates involved in exuviae consumption can directly transfer such resources to individuals engaged in reproduction (the queen) or growth (larvae). This study investigates whether incipient colonies of C. gestroi (Wasmann) can gain additional biomass when they are fed supplementary exuviae. Incipient colonies were reared in nitrogen-poor or nitrogen-rich conditions, and 0, 1, 5, or 10 exuviae were added to 3-month-old colonies. After 6.5 months, colonies reared in nitrogen-poor environments gained significantly more biomass when exuviae were added than colonies with no added exuviae. However, the addition of exuviae had no effect on colony growth for colonies reared in nitrogen-rich environments. In a second experiment, queens from colonies in which exuviae were effectively removed laid fewer eggs than queens from colonies in which exuviae were not removed. Therefore, consumption of exuviae from molting individuals by nestmates is an important part of the nitrogen recycling strategy in Coptotermes colonies, as it facilitates queen oviposition and colony growth, especially when such colonies have limited access to nitrogen-rich soils.

Colony-age-dependent variation in cuticular hydrocarbon profiles in subterranean termite colonies.

Cuticular hydrocarbons (CHCs) have, in insects, important physiological and ecological functions, such as protection against desiccation and as semiochemicals in social taxa, including termites. CHCs are, in termites, known to vary qualitatively and/or quantitatively among species, populations, castes, or seasons. Changes to hydrocarbon profile composition have been linked to varying degrees of aggression between termite colonies, although the variability of results among studies suggests that additional factors might have been involved. One source of such variability may be colony age, as termite colony demographics significantly change over time, with different caste and instar compositions throughout the life of the colony. We here hypothesize that the intracolonial chemical profile heterogeneity would be high in incipient termite colonies but would homogenize over time as a colony ages and accumulates older workers in improved homeostatic conditions. We studied caste-specific patterns of CHC profiles in Coptotermes gestroi colonies of four different age classes (6, 18, 30, and 42 months). The CHC profiles were variable among castes in the youngest colonies, but progressively converged toward a colony-wide homogenized chemical profile. Young colonies had a less-defined CHC identity, which implies a potentially high acceptance threshold for non-nestmates conspecifics in young colonies. Our results also suggest that there was no selective pressure for an early-defined colony CHC profile to evolve in termites, potentially allowing an incipient colony to merge nonagonistically with another conspecific incipient colony, with both colonies indirectly and passively avoiding mutual destruction as a result.

Evaluating an Alleged Mimic of the Monarch Butterfly: Neophasia (Lepidoptera: Pieridae) Butterflies are Palatable to Avian Predators.

Some taxa have adopted the strategy of mimicry to protect themselves from predation. Butterflies are some of the best representatives used to study mimicry, with the monarch butterfly, Danaus plexippus (Lepidoptera: Nymphalidae) a well-known model. We are the first to empirically investigate a proposed mimic of the monarch butterfly: Neophasia terlooii, the Mexican pine white butterfly (Lepidoptera: Pieridae). We used captive birds to assess the palatability of N. terlooii and its sister species, N. menapia, to determine the mimicry category that would best fit this system. The birds readily consumed both species of Neophasia and a palatable control species but refused to eat unpalatable butterflies such as D. plexippus and Heliconius charithonia (Lepidoptera: Nymphalidae). Given some evidence for mild unpalatability of Neophasia, we discuss the results considering modifications to classic mimicry theory, i.e., a palatability-based continuum between Batesian and Müllerian mimicry, with a quasi-Batesian intermediate. Understanding the ecology of Neophasia in light of contemporary and historical sympatry with D. plexippus could shed light on the biogeography of, evolution of, and predation pressure on the monarch butterfly, whose migration event has become a conservation priority.

Behavioral Evidence for Host Transitions in Plant, Plant Parasite, and Insect Interactions.

Specialized herbivorous insects have the ability to transition between host plant taxa, and considering the co-evolutionary history between plants and the organisms utilizing them is important to understanding plant insect interactions. We investigated the role of a pine tree parasite, dwarf mistletoe (Arceuthobium spp.) M. Bieb. Santalales: Viscaceae, in mediating interactions between Neophasia (Lepidoptera: Pieridae) butterflies and pine trees, the butterflies' larval hosts. Mistletoe is considered the butterflies' ancestral host, and the evolutionary transition to pine may have occurred recently. In Arizona, United States, we studied six sites in pine forest habitats: three in Neophasia menapia (Felder and R. Felder, 1859) habitat and three in Neophasia terlooii Behr, 1869 habitat. Each site contained six stands of trees that varied in mistletoe infection severity. Butterfly behavior was observed and ranked at each stand. Volatile compounds were collected from trees at each site and analyzed using gas chromatography-mass spectroscopy. Female butterflies landed on or patrolled around pine trees (i.e., interacted) more than males, and N. terlooii interacted more with pine trees than N. menapia. Both butterfly species interacted more with tree stands harboring greater mistletoe infection, and N. terlooii interacted more with heavily infected tree stands than did N. menapia. The influence of mistletoe on Neophasia behavior may be mediated by differences in tree volatiles resulting from mistletoe infection. Volatile profiles significantly differed between infected and uninfected pine trees. The role of mistletoe in mediating butterfly interactions with pines has implications for conservation biology and forest management, and highlights the importance of understanding an organism's niche in an evolutionary context.