Ecology of the Walkingstick

Abstract Ecological life history studies with walkingsticks in northern Indiana were conducted to describe and quantify seasonal activity changes and to determine the nature of diet behavior. Walkingstick eggs overwinter in the leaf litter and begin to hatch in mid-June during the evenings when ground level humidity exceeds 80 percent; normally 90 percent of the hatch is completed by the second week in July. Newly emerged nymphs immediately begin climbing the understory vegetation. Although black oak is the major ultimate host species, initial feeding is greater on white oak and black cherry whose presence is a significant factor in early nymphal survival. Walkingsticks exhibit a well-defined diel feeding periodicity peaking between 2100 and 0300 hours; frass deposition is positively and closely related to the daily temperature cycle. Walkingstick densities in the tree crowns increase as the hatch progresses, but wind and overcrowding dislodge the insects to result in a continuous vertical cycling of insects through the growth season. Walkingsticks usually require 5 stadia before reaching the adult stage, but some males can mature in 4 instars and a few females require 6. Difficulty in field identification of stages necessitated the use of mean walkingstick length as an index for seasonal development. An equation describing the relationship between temperature and walkingstick development is given. Walkingstick nymphs require approximately 1835 day-degrees (base 48°F = 8.9°C) to complete immature development. Oviposition begins by early September when 20-35 percent of the population is in the adult stage. Eggs are laid principally between 1500 and 0300 hours, with peak deposition occurring about 1800. As might be expected, maximal seasonal oviposition occurs when most of the population is in the adult stage, but is closely linked with favorable temperatures. Cold periods reduce oviposition and accelerate mortality. The generation terminates when green foliage disappears in late October. A sex ratio of 50:50 is evident when several consecutive generations are combined, but the ratio varies from season to season. Severe defotiation by walkingsticks significantly reduces black oak radial growth. Forest Sci. 23:45-63.