Appendix 17 Sieve construction for larval and post-larval collection

Note: Refer to Technical Drawings – Pg 14 and Pg 17.
1. Cut with a circular saw a PVC ring to appropriate height (20 cm high for 20 cm and 25 cm larval sieves, 18 cm high for raceways).

2. Sand surface sieve on both ends to make it as smooth as possible.
3. For a 20 cm sieve for larval collection, drill two 15 mm hole on opposite sides, approximately 40 mm from top. For a 30 cm sieve for outdoor raceway, drill one 25 mm hole 50 mm from top.
4. Cut a square piece of mesh required so as to cover entire surface area of sieve. 5. Lay mesh on top.
6. Adjust hose clamp so that it can be placed on top of mesh and sieve; enough mesh should be available so that it sticks out below hose clamp.
7. Tighten hose clamp along top of sieve with a screwdriver, continuously pulling mesh.
8. Try to eliminate wrinkles in mesh by pulling uniformly around perimeter of sieve.
9. Label size of mesh on side of PVC with a permanent marker.
10. Once mesh is tight and hose clamp secured (approximately 1 cm from top of sieve) use PVC cleaner to prepare surface of sieve for gluing.
11. Glue mesh to PVC using PVC glue (or cement) along surface and side down to hose clamp.
12. Let dry for 24 hours.

13. Once dry, make sure mesh is uniformly glued so that larvae cannot accumulate in small unglued areas.
14. Remove hose clamp and cut unglued mesh with a razor blade.
15. For support rings used in larval collection, cut 25 cm diameter pipe in 2.5 cm height.
16. For larval collection and with 6 larval tanks, two sets of rings (20 cm and 25 cm diameter) of same mesh aperture are used, allowing take down of two larval tanks simultaneously. Approximately 10–15 mm pipes were cut to 30 cm length for suspension of 20 cm sieve onto 25 cm sieve.
17. A total of 16 sieves for post-larval settlement, suspended in indoor raceway are used in the present set-up.
18. A total of 12 sieves for outdoor raceway are used in the present set-up.
19. A range of sieves, with mesh size ranging from 1.2 mm in diagonal to 4.9 mm, are used in the present set-up for grading.