Porous plates for manhole cover

Porous plates for manhole cover which allow water flowing in but avoid mosquito flying out. Type 1 is for L=143mm,R=11mm,H=32mm. Type 2 is for L=130mm,R=11mm,H=28mm. Type 3 is for L=137mm,R=8mm,H=24mm. Currently the hole diameter on the porous plate is 3mm, and this size is needed to be tested if mosquito can come out. Later I found other design for similar propose on web (https://tw.appledaily.com/new/realtime/20151019/714448/).