The order Zoraptera is one of the least diverse and most poorly understood of insect lineages. Zoraptera are minute, hemimetabolous insects superficially resembling barklice (Psocoptera) or termites (Isoptera). Individuals are generally less than 3 mm in total body length, exclusive of their antennae, and are gregarious. Overall, zorapterans are quite homogenous in their morphology and tend to be off-white (mostly nymphs) to brown in color. Individuals of each species occur in two morphs: eyed and winged forms that then shed their wings after dispersal or blind and apterous forms that predominate in colonies. The order consists of a single family, Zorotypidae, presently with two recognized genera. Only one, very preliminary attempt has been made to elucidate phylogenetic relationships among zorapteran species (Engel, 2003b). A complete monograph of the order has been in preparation for many years and should be finished in the next 3-4 years (Engel, unpubl.)
Zorapterans live in small colonies of 15-120 individuals which they found in the crevices or under dead bark of moist, decaying logs (they will also colonize man-made sawdust piles). Species feed principally on fungal hyphae and spores but can also be general scavengers or predators, victimizing nematodes, mites, or other tiny arthropods. Other aspects of their biology and behavior are considered by Choe (1994a, 1994b, 1995, 1997), Engel (2003a), and Valentine (1986).
Although considered rare by many entomologists, once a successful "search-image" is developed for locating zorapteran habitats, then species are typically not difficult to locate. In fact, the "rarity" of zorapterans may be merely apparent and more a result of poor collecting than any actual scarcity. Certainly some species are uncommon, but overall the actual abundance of the order likely does not live up to its reputation for scant occurrence (this is particularly true for the North American species, Zorotypus hubbardi: Engel, pers. obs.). Wilson (1959) went so far as to identify a "Zoraptera stage" in decomposition whereby logs can be easily torn with an ordinary collecting tool. Naturally-formed spaces in logs not reached by light harbor zorapteran colonies. Once the wood is disturbed individuals will quickly scatter to avoid detection, thus fogging with a general insecticide prior to dissecting a log can aid collection. Individuals are best preserved in ethanol.
Zorapterans are principally distributed pantropically with only four species occurring North of the Tropic of Cancer (i.e., North of 23.5°N): Z. hubbardi in the United States, Z. snyderi in Florida, and Z. sinensis and Z. medoensis in Tibet. Almost all of the northernmost records for Zorotypus in North America are from sawdust piles rather than natural logs suggesting that the distribution in regions with considerable winter frosts is artificially influenced by human activity (Engel, 2003a, 2004). The effects of global climate change on northern migrations of Zorotypus are uncertain but are likely to permit species to expand their distributions significantly in North America and Asia. Aside from the aforementioned four species, all zorapterans are tropical. Even those fossil records of Zoraptera are all from ambers formed in warm-tropical paleoclimates (Engel and Grimaldi, 2002). While species have at times been considered highly endemic and hypothesized to have poor dispersal abilities, increasingly individual species are being discovered to have larger geographic ranges than previously understood (e.g., New, 2000; Engel, 2001). Such species provide evidence of some degree of dispersal ability in zorapterans so as to maintain specific integrity over these ranges. Furthermore, the presence of zorapterans on distantly isolated islands of relatively recent geological age such as Hawaii indicates some dispersal capabilities.
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