Within‐generation dynamics of leatherjackets (Tipula paludosa Meig.)

Abstract

Larvae of Tipula paludosa (leatherjackets) are pests of grassland and cereals, and important prey items for a range of farmland birds. Their population dynamics from year to year have been the subject of study, but within‐generation dynamics have received much less attention. The duration and occurrence of instars and size of the population is important to both pest management and bird conservation. Leatherjackets were collected monthly from four grass fields over five generations (October to September). Count data were analysed for sources of variability and used to estimate the timing and duration of instars and population changes over a single generation. Instar durations were correlated with temperature. From the first to third instars, sample counts were strongly influenced by the location of the site and the generation. Fourth instar larvae showed a similar decline in numbers across all sites and generations. The duration and timing of first to third instars was more variable than that of the fourth instar, but there was limited evidence that this was influenced by temperature. Only the durations of the third and fourth instars were correlated. The population decline from April to September coincided with the onset of the fourth instar. Our results show that the factors influencing leatherjacket numbers change over the life cycle, but by the fourth instar, these are biotically driven. The predictability of its numerical decline indicates defined windows for crop damage and availability as prey. The stability of its timing suggests that day length may synchronize the annual cycle. Fixed timing of the fourth instar will have important consequences for the timing of crop damage and the conservation of farmland birds as climate changes.

Mid-winter temperatures, not spring temperatures, predict breeding phenology in the European starlingSturnus vulgaris

“…3.3 in [ 4 ]), and this is probably key in explaining the high breeding synchrony. In particular, tipulid growth is temperature-sensitive [ 32 , 52 , 53 ] with growth rate being slowest at low temperatures in December–February. Both growth rate and size of larvae appear to be determined by the field conditions to which they are exposed early in their development, and larval growth rate is positively related to asymptotic larval weight [ 54 ].…”

Linking the spatio‐temporal distribution of an edaphic crane fly to its heterogeneous soil environment

“…The within‐generation population dynamics of T . paludosa has been documented, but timings may differ by climatic region (Petersen, ) and across native (Blackshaw & Moore, ) and invasive (Jackson & Campbell, ) ranges. A general life cycle for the northeastern USA is provided here.…”

Synchronized Dynamics of Tipula paludosa Metapopulation in a Southwestern Scotland Agroecosystem: Linking Pattern to Process

“…However, a significant effect (that may even result in a population crash) is only seen when weather conditions in September/October are exceptionally dry (Milne et al 1965). On the other hand, temperature was shown to have little effect on T. paludosa dynamics (Blackshaw and Moore 2012). Correspondingly, other studies suggest that the environmental factors may be less significant than the effects of population density, especially in a harsh environment.…”