The Size of Particles Ingested by Moorland Stream Blackfly Larvae (Simuliidae)

The length of particles in the guts of final instar blackfly larvae from moorland streams was examined on 0.45 ,um pore-size 'Sartorius' membrane-filters. For S. vernum, S. monticola and S. nitidifrons mean length ranged from 1.4 ? 1.4 ,um to 2.6 ? 10.6 Am with an overall range of 0.5 ,m to 258 ,m. In all larval guts over 50% of particles were less than 1 ,m long. The particle regime in the guts of final instar larvae of S. nitidifrons showed a significant positive correlation with that of the stream water. Experiments with latex microspheres, confirmed this finding and demonstrated that a wide length range of S. nitidifrons larvae do not select particles on the basis of size. This was also true for larvae of S. vernum and S. aureum.