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Universities use prerequisites to regulate the path of students through a program or major. However, the impact of prerequisites on follow-up courses in anatomy and physiology is not well understood. If success in follow-up courses depends on completion of prerequisite courses, then students should earn higher grades on exam questions that assess prerequisite knowledge. To test this hypothesis, we investigated the potential impact of a required prerequisite human physiology lecture course on a followup human physiology laboratory course and a follow-up molecular pharmacology course. We also investigated the potential impact of a recommended prerequisite human physiology laboratory course on a follow-up human anatomy course. We assessed student exam performance in the follow-up courses based on their familiarity with the material from the required prerequisite course or the recommended prerequisite course. Our results were mixed and demonstrated limited performance gains in the follow-up courses despite overlap of material among the courses. These results suggest that prerequisite courses may not have a significant impact on the outcome of future related courses and that individual academic programs should evaluate the effectiveness of prerequisite courses in a local context.

Different versions of multiple-choice exams were administered to an undergraduate class in human physiology as part of normal testing in the classroom. The goal was to evaluate whether the number of options (possible answers) per question influenced the effectiveness of this assessment. Three exams (each with three versions) were given to each of two sections during an academic quarter. All versions were equally long, with 30 questions: 10 questions with 3 options, 10 questions with 4, and 10 questions with 5 (always one correct answer plus distractors). Each question appeared in all three versions of an exam, with a different number of options in each version (three, four, or five). Discrimination (point biserial and upper-lower discrimination indexes) and difficulty were evaluated for each question. There was a small increase in difficulty (a lower average score on a question) when more options were provided. The upper-lower discrimination index indicated a small improvement in assessment of student learning with more options, although the point biserial did not. The total length of a question (number of words) was associated with a small increase in discrimination and difficulty, independent of the number of options. Quantitative questions were more likely to show an increase in discrimination with more options than nonquantitative questions, but this effect was very small. Therefore, for these testing conditions, there appears to be little advantage in providing more than three options per multiple-choice question, and there are disadvantages, such as needing more time for an exam.

The mechanical properties of bed bug (Cimex lectularius L.) tarsi and pretarsi were investigated in order to evaluate their vulnerability to piercing by plant trichomes (sharp microscopic hairs). Nanoindentation was used to measure the force required to insert a sharp probe into the cuticle of these different regions, as well as to determine creep and reduced elastic moduli for the cuticle. Scanning electron microscopy was used to visualize the indents that had been generated by nanoindentation. The force required to insert a cube corner nanoindenter probe into the cuticle was determined for a range of displacements (1 to 9 μm) and strain rates (0.003 to 0.5 s-1). Greater force was required to insert this sharp probe at greater depth or at faster strain rates. A specific region of the pretarsus (membrane with microtrichia) more frequently pierced by trichomes during bed bug locomotion required approximately 20-30% less force, exhibited more creep, and had a lower reduced elastic modulus for the first micron of indentation compared to the other regions; although this pattern was not consistent for greater displacements. These mechanical attributes, which will facilitate the initial stage of puncture in addition to the presence of natural infoldings in the cuticle of this area, may make that area of the pretarsus particularly vulnerable to piercing. This information will help inform development of physical methods for control of insect pests such as bed bugs.

BackgroundThe resistance of bed bugs (Cimex lectularius L.) to chemical insecticides has motivated the development of non-chemical control methods such as heat treatment. However, because bed bugs tend to hide in cracks or crevices, their behavior incidentally generates a thermally insulated microenvironment for themselves. Bed bugs located on the outer surface of luggage are less insulated and potentially more vulnerable to brief heat treatment.ResultsSoft-sided suitcases with adult male bed bugs on the outside were exposed to an air temperature of 70-75 °C. It took 6 min to kill all of the bed bugs, even those that had concealed themselves under zipper flaps or decorative piping. During heating, only one bed bug (out of 250 in total) moved into the luggage (through a closed zipper). Over long periods of time (24 h) at room temperature, adult male bed bugs on the exterior of luggage only infrequently moved inside; only 3% (5/170) had moved inside during 24 h.ConclusionsBrief exterior heat treatment of luggage is a promising way to reduce the spread of bed bugs being transported on the outer surface of luggage. This treatment will not kill bed bugs inside the luggage, but could be a component of integrated management for this pest. © 2016 Society of Chemical Industry.

Insect antennae are important mechanosensory and chemosensory organs. Insect appendages, such as antennae, are encased in a cuticular exoskeleton and are thought to bend only between segments or subsegments where the cuticle is thinner, more flexible, or bent into a fold. There is a growing appreciation of the dominating influence of folds in the mechanical behavior of a structure, and the bending of cricket antennae was considered in this context. Antennae will bend or deflect in response to forces, and the resulting bending behavior will affect the sensory input of the antennae. In some cricket antennae, such as in those of Acheta domesticus, there are a large number (>100) of subsegments (flagellomeres) that vary in their length. We evaluated whether these antennae bend only at the joints between flagellomeres, which has always been assumed but not tested. In addition we questioned whether an antenna undergoes a length change as it bends, which would result from some patterns of joint deformation. Measurements using light microscopy and SEM were conducted on both male and female adult crickets (Acheta domesticus) with bending in four different directions: dorsal, ventral, medial, and lateral. Bending occurred only at the joints between flagellomeres, and antennae shortened a comparable amount during bending, regardless of sex or bending direction. The cuticular folds separating antennal flagellomeres are not very deep, and therefore as an antenna bends, the convex side (in tension) does not have a lot of slack cuticle to "unfold" and does not lengthen during bending. Simultaneously on the other side of the antenna, on the concave side in compression, there is an increasing overlap in the folded cuticle of the joints during bending. Antennal shortening during bending would prevent stretching of antennal nerves and may promote hemolymph exchange between the antenna and head.

Insect antennae are important mechanosensory and chemosensory organs. Insect appendages, such as antennae, are encased in a cuticular exoskeleton and are thought to bend only between segments or subsegments where the cuticle is thinner, more flexible, or bent into a fold. There is a growing appreciation of the dominating influence of folds in the mechanical behavior of a structure, and the bending of cricket antennae was considered in this context. Antennae will bend or deflect in response to forces, and the resulting bending behavior will affect the sensory input of the antennae. In some cricket antennae, such as in those of Acheta domesticus, there are a large number (>100) of subsegments (flagellomeres) that vary in their length. We evaluated whether these antennae bend only at the joints between flagellomeres, which has always been assumed but not tested. In addition we questioned whether an antenna undergoes a length change as it bends, which would result from some patterns of joint deformation. Measurements using light microscopy and SEM were conducted on both male and female adult crickets (Acheta domesticus) with bending in four different directions: dorsal, ventral, medial, and lateral. Bending occurred only at the joints between flagellomeres, and antennae shortened a comparable amount during bending, regardless of sex or bending direction. The cuticular folds separating antennal flagellomeres are not very deep, and therefore as an antenna bends, the convex side (in tension) does not have a lot of slack cuticle to unfold and does not lengthen during bending. Simultaneously on the other side of the antenna, on the concave side in compression, there is an increasing overlap in the folded cuticle of the joints during bending. Antennal shortening during bending would prevent stretching of antennal nerves and may promote hemolymph exchange between the antenna and head.

Resurgence in bed bug infestations and widespread pesticide resistance have greatly renewed interest in the development of more sustainable, environmentally friendly methods to manage bed bugs. Historically, in Eastern Europe, bed bugs were entrapped by leaves from bean plants, which were then destroyed; this purely physical entrapment was related to microscopic hooked hairs (trichomes) on the leaf surfaces. Using scanning electron microscopy and videography, we documented the capture mechanism: the physical impaling of bed bug feet (tarsi) by these trichomes. This is distinct from a Velcro-like mechanism of non-piercing entanglement, which only momentarily holds the bug without sustained capture. Struggling, trapped bed bugs are impaled by trichomes on several legs and are unable to free themselves. Only specific, mechanically vulnerable locations on the bug tarsi are pierced by the trichomes, which are located at effective heights and orientations for bed bug entrapment despite a lack of any evolutionary association. Using bean leaves as templates, we microfabricated surfaces indistinguishable in geometry from the real leaves, including the trichomes, using polymers with material properties similar to plant cell walls. These synthetic surfaces snag the bed bugs temporarily but do not hinder their locomotion as effectively as real leaves.

The air flow pattern expected around a cylindrical object such as a tree in slow wind, is predicted from fluid mechanics to have areas of faster flow (upwind) and slower recirculating flow with eddies (downwind). An organism located on the surface of a tree would experience different flow depending on its circumferential position. If that organism was searching for a chemical signal, such as a pheromone plume, it might maximize its probability of chemodetection by placing itself in areas of greatest flow speed (the upwind surface of the cylinder, i.e., in front of the separation points). We tested whether wood cockroaches in the genus Parcoblatta exhibit such upwind positioning; they live in forests, and males actively fly from tree to tree, while searching for females releasing sex pheromone. In contrast to an expectation of upwind preference, male cockroaches were evenly distributed around trees relative to upwind (measured with a novel "feather boa" flow visualization technique), even though the wind direction was relatively steady. We investigated whether sex pheromone could be detected at any location around a cylindrical surface in a laboratory flow chamber by using Bombyx mori wing fanning as a bioassay. Although upwind moths arrayed on the surface detected pheromone more rapidly, pheromone detection occurred at least a third of the time at any position, which could explain the even distribution of Parcoblatta males around trees.

Trains of 20-ms-duration pulses of pheromone were delivered at rates of 1-33 Hz to antennal preparations of males of Bombyx mori and Lymantria dispar, two moth species with bipectinate antennae. Resolution of rapidly pulsed plumes of pheromone was not compromised by a complex antennal morphology or by moderate changes in wind speed (25-50 cm/s). Fourier analysis of the electroantennograms resolved the temporal structure of the signal at frequencies up to 25 Hz for B. mori and up to 5 Hz for L. dispar. The ability of these sensory structures to identify the original (unchanged) frequency of the pulse train is particularly noteworthy because air is slowed by about an order of magnitude as it passes through bipectinate antennae. Although an unchanging frequency in slowed airflow may be counterintuitive, this flow pattern, and its effects on odorant patch shape and spacing, is explained from fluid mechanical principles (i.e., the principle of continuity). An unchanging frequency suggests that as decelerating air passes through a bipectinate antenna, the slowed patches of odorant are stretched, thinned, and brought closer together by the same factor with which they are slowed.

Pectinate (feathery) antennae have high resistance to air flow, and therefore most of the air approaching an antenna is diverted around it and is not available for chemical sampling by the sensory hairs on that antenna. The small fraction (approximately 10-20%) of approaching air that passes through the air spaces or gaps in the antenna decelerates and the streamlines diverge as the air approaches the antenna. Sampling a small fraction of air that is decelerating and diverging has consequences for chemoreception that are described here for the first time. The behavior of the air is predicted from application of a fluid mechanical law: the principle of continuity. As this small fraction of air decelerates and flows through the air gaps in the antenna, it will be "stretched" in the plane perpendicular to the air flow. Therefore, the air may be sampled by the sensory hairs at a greater spatial resolution than expected from the distribution of the odorant molecules in the air upstream of the antenna. However, the slowing down of odorant-laden air as it passes through an antenna will not change the perceived temporal characteristics of the chemical stimulus (e.g., the rate of odorant filament encounter). This distortion or stretching of the air sample is expected to develop within about one antennal width upstream of the antenna, as verified by examining wakes of simple physical models.

Dimensionless numbers are very useful in characterizing mechanical behavior because their magnitude can often be interpreted as the relative importance of competing forces that will influence mechanical behavior in different ways. One dimensionless number, the Womersley number (Wo), is sometimes used to describe the unsteady nature of fluid flow in response to an unsteady pressure gradient; i. e., whether the resulting fluid flow is quasi-steady or not. Fluids surround organisms which themselves contain fluid compartments; the behaviors exhibited by these biologically-important fluids (e.g. air, water, or blood) are physiologically significant because they will determine to a large extent the rates of mass and heat exchange and the force production between an organism and its environment or between different parts of an organism. In the biological literature, the use of the Womersley number is usually confined to a single geometry: the case of flow inside a circular cylinder. We summarize the evidence for a broader role of the Womersley number in characterizing unsteady flow than indicated by this geometrical restriction. For the specific category of internal flow, we show that the exact analytical solution for unsteady flow between two parallel walls predicts the same pattern of fluid behavior identified earlier for flow inside cylinders; i.e., a dichotomy in fluid behavior for values of Wo < 1 and Wo > 1. When Wo < 1, the flow is predicted to faithfully track the oscillating pressure gradient, and the velocity profiles exhibit a parabolic shape such that the fluid oscillating with the greatest amplitude is farthest from the walls ("quasi-steady" behavior). When Wo > 1, the velocity profiles are no longer parabolic, and the flow is phase-shifted in time relative to the oscillating pressure gradient. The amplitude of the oscillating fluid may either increase or decrease as Wo > 1, as described in the text.

Physiological Systems in Insects. Marc J. Klowden. Academic Press, San Diego, 2002. 415 pp., illus. $59.95 (ISBN 0124162649 paper). Insect Physiology and Biochemistry. James L. Nation. CRC Press, Boca Raton, [...]

Shorter books get read. In part, this motivated Heinrich to write another, but shorter, book on insect thermal biology. Heinrich's earlier book, The hot-blooded insects, appeared in 1992 and is [...]