Abstract
Modern grylloblattids are one of the least diverse of the modern insect orders. The thorax changes in morphology might be associated with the changes of the function of the forelegs, wing loss, changes in behavior and adaptation to habitat. As temperature is the main barrier for migration of modern grylloblattids, the range of each species is extremely limited. The potential distribution areas of grylloblattids remain unclear. A second new species of ice crawlers (Insecta: Grylloblattodea), Grylloblattella cheni Bai, Wang et Yang sp. nov., is described from China. The distribution map and key to species of Grylloblattella are given. A comparison of the thorax of extant and extinct Grylloblattodea is presented, with an emphasis on the pronotum using geometric morphometric analysis, which may reflect thorax adaptation and the evolution of Grylloblattodea. Potential global distribution of grylloblattids is inferred. Highly diversified pronota of extinct Grylloblattodea may reflect diverse habitats and niches. The relatively homogeneous pronota of modern grylloblattids might be explained by two hypotheses: synapomorphy or convergent evolution. Most fossils of Grylloblattodea contain an obviously longer meso- and metathorax than prothorax. The length of the meso- and metathorax of modern grylloblattids is normally shorter than the prothorax. This may be associated with the wing loss, which is accompanied by muscle reduction and changes to the thoracic skeleton system. Threats to grylloblattids and several conservation comments are also provided.
Highlights
Modern grylloblattids, all occur northward of,35u latitude in cooltemperate areas of the United States, Canada, Russia, Japan, Korea and China, and they are restricted to cold and extreme habitats that are difficult to access
The relationships between grylloblattodean fossil taxa and the modern grylloblattids remain unclear because most fossils are based on isolated wings or have poorly preserved body features
Wheeler et al [17] proposed that the modern Grylloblattidae were the sister group of the Dermaptera, being together the sister group of (Phasmida + Orthoptera), and that the (Plecoptera + Embioptera) were not directly related to this clade
Summary
Modern grylloblattids ( known as ice bugs, ice crawlers, and rock crawlers), all occur northward of ,35u latitude in cooltemperate areas of the United States, Canada, Russia, Japan, Korea and China, and they are restricted to cold and extreme habitats that are difficult to access. Grylloblattids are generally found on northfacing talus slopes, snow patches near forest at high elevations (1500–3000 m), in caves with permanent ice at low elevations (300– 1000 m) [3,4], and some Grylloblattina are from 5 m–300 m, much lower than most other grylloblattids [5]. They live on and in soil, in caves, and beneath stones and in crevices of mountainous regions. They are principally carrion feeders on other insects, though they will consume plant material, fungus, and detritus [6]
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