Biology of tipula paludosa; growth of the larva in the field
1967
Laughlin, Roger
Tipula paludosa has an annual life cycle. The larval stage lasts from September to the following August. Larvae were collected from 16 fields in Northumberland and Cumberland at all times of year in the 10-year period 1954-1963. Larvae were individually weighed. The weights were used a) to construct curves showing the course of growth through the year and b) to compare average size of individuals from different places and different years. A growth curve was also constructed from the weights of larvae kept in the field under semi-natural conditions. Larvae grow extremely fast in the autumn, slowly through the winter and moderately fast in the spring and early summer. First instar larvae are present for only a few weeks in the autumn. Second and third instars are usually present in the population throughout the winter. Most larvae undergo the third moult in a restricted period in the spring just after the soil begins to warm up. The weight of larvae at the third moult is a convenient index of size of individual. Variation in mean weight between place-years was not significantly greater than variation within each field. Peak weight of larvae, on the other hand, did vary significantly from year to year though probably not from place to place in any one year. Pupal weight figures showed that females varied more than males from year to year. Since pupal weight is positively correlated with fecundity, larval spring growth is of importance in determining the number of eggs laid the following autumn. However, it is suggested that, from an economic point of view, the correlation between size and pasture damage is of more interest.
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