28The evolutionary transition between winglessness and a full-winged morphology requires 29 selective advantage for intermediate forms. Conversely, repeated secondary wing 30 reductions among the pterygotes indicates relaxation of such selection. However, 31 evolutionary trajectories of such transitions are not well characterized. The stick insects 32 (Phasmatodea) exhibit diverse wing sizes at both interspecific and intersexual levels, and 33 thus provide a system for examining how selection on flight capability, along with other 34 selective forces, drives the evolution of flight-related morphology. Here, we examine 35 variation in relevant morphology for stick insects using data from 1100+ individuals 36 representing 765 species. Although wing size varies along a continuous spectrum, taxa 37 with either long or miniaturized wings are the most common, whereas those with 38 intermediate-sized wings are relatively rare. In a morphological space defined by wing 39 and body size, the aerodynamically relevant parameter termed wing loading (the average 40 pressure exerted on the air by the wings) varies according to sex-specific scaling laws; 41 volant but also flightless forms are the most common outcomes in both sexes. Using 42 phylogenetically-informed analyses, we show that wing size and body size are correlated 43 in long-wing insects regardless of sexual differences in morphology and ecology. These 44 results demonstrate the diversity of flight-related morphology in stick insects, and also 45 provided a general framework for addressing evolutionary coupling between wing and 46 body size. We also find indirect evidence for a 'fitness valley' associated with 47 intermediate-sized wings, suggesting relatively rapid evolutionary transitions between 48 wingless and volant forms.49 50 51 Keywords 52 53 body size, evolution, flight, phasmid, sexual dimorphism, wing size 54 55 56 57 Symbols and abbreviations 58 Aw Wing area 59 pw Wing loading 60 L Body length 61 Lw Wing length 62 m Mass 63 SSD Sexual size dimorphism 64 SWD Sexual wing dimorphism 65 Q Relative wing size 66 ΔL Sexual size dimorphism index 67 ΔQ Sexual wing dimorphism index 68 69 70 71 3 1. Introduction 72 73 Flight is fundamental to the ecology and evolutionary diversification of pterygote insects by 74 allowing for three-dimensional mobility and greater access to nutritional resources (Dudley, 75 2000). Nonetheless, approximately 5% of the extant pterygote fauna is flightless (Roff, 1994), 76 and various conditions of reduced wing size (e.g., brachyptery and microptery) are found across 77 the neopteran orders. Given structural costs and high energy expenditure during flight, 78 maintenance of the flight apparatus is not universally favored by selection. Partial reduction or 79 complete loss of wings is associated with various morphological and ecological factors, such as 80 developmental tradeoffs, enhanced female fecundity, and reduced demand for aerial mobility in 81certain habitats (Roff, 1990; Roff, 1994). In these cases, smaller wings exhibit redu...

The evolutionary transition between winglessness and a full-winged morphology requires selective advantage for intermediate forms. Conversely, repeated secondary wing reductions among the pterygotes indicates relaxation of such selection. However, evolutionary trajectories of such transitions are not well-characterized. The stick insects (Phasmatodea) exhibit diverse wing sizes at both interspecific and intersexual levels, and thus provide a system for examining how selection on flight capability, along with other selective forces, drives the evolution of flight-related morphology. Here, we examine variation in relevant morphology for stick insects using data from 1,100+ individuals representing 765 species. Although wing size varies along a continuous spectrum, taxa with either long or miniaturized wings are the most common, whereas those with intermediate-sized wings are relatively rare. In a morphological space defined by wing and body size, the aerodynamically relevant parameter termed wing loading (the average pressure exerted on the air by the wings) varies according to sex-specific scaling laws; volant but also flightless forms are the most common outcomes in both sexes. Using phylogenetically-informed analyses, we show that relative wing size and body size are inversely correlated in long-winged insects regardless of sexual differences in morphology and ecology. These results demonstrate the diversity of flight-related morphology in stick insects, and also provide a general framework for addressing evolutionary coupling between wing and body dimensions. We also find indirect evidence for a "fitness valley" associated with intermediate-sized wings, suggesting relatively rapid evolutionary transitions between wingless and volant forms.

College students' attrition in engineering programs is a major problem in developed and developing countries. Outreach activities in science, technology, engineering, and mathematics are a powerful resource to ignite K-12 students' interest to pursue scientific and engineering careers. Here, a program on mechatronics for Malaysian high-schoolers developed at the New York University Tandon School of Engineering and implemented at the National University of Malaysia is presented. The program follows a dual model where instructors and students work together on a project-based learning curriculum inspired by real-world problems. A group of Malaysian graduate students and highschool teachers was trained to serve as instructors by the New York University team. After training, the New York University team aided the instructors to administer the curriculum to 100 high-schoolers and organize a one-day exhibit for families at the