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LAND PATHWAYS AND VECTORS __C land pathway includes highways, roads, trails, and paths that could be used to transport zebra mussels. The primary means of long distance I overland dispersal of zebra mussels has been by transport on small boats on trailers (Griffiths et al. 1991). It is presumed that transport of zebra mussel by land pathways would principally occur by transport of boats that have zebra mussels attached to them, or by transferring contaminated equipment, such as nets and live wells, from one body of water to another. Adult zebra mussels may be entangled in nets and equipment, or the free- living larva may also be present in water entrapped in the boat motor, live well, or any other moist area. Zebra mussels that are attached to boat hulls and other exposed areas can be killed in hot weather (e.g., if exposed for 2 days at 35°C; Jenner and Janssen-Mommen 1992). However, recent studies have shown that even at about 0% relative humidity, it takes an exposure duration of at least 3 days (McMahon et al. 1993) to kill adult zebra mussels at 25°C, and more than 10 days is required if the temperature is 15°C or less. Thus, it is likely that adult zebra mussels could be inadvertently transported to the West by boaters, especially during cool weather. The zebra mussel has been found as far west as Wisconsin, Iowa, Missouri, Arkansas, and Louisiana, and it was recently found in the Arkansas River in Oklahoma (Figure 2). Although yet undetected, it probably invaded the Missouri River system via barge traffic to the head of navigation at Sioux City, Iowa, and it may soon be found in the waters of Nebraska, South Dakota, and North Dakota. It is also presumed that there may be further invasion into Oklahoma, Texas, Kansas, Colorado, and New Mexico from the Arkansas River, Because there has been widespread dispersal and transport of zebra mussels in Canadian waters, the