Observation of dead insects in dust fall-out buckets

In some of the dust monitoring units in various areas (especially the wheat fields in South Africa) a seasonal occurrence of insects falling into the collection buckets is being experienced. Insects observed were mostly mosquitoes, flies & other unknown species. This seems to be only happening in buckets facing west and north.

Using the SS strainer the insects were unable to be removed completely, about 25-30 % still remain in the buckets. This photograph was taken after removing 50% of insects from the bucket.


From the photograph it can be seen that the insects are small and some would pass through the 1mm sieve. The sieve should be placed on top of the Buchner Funnel when the filtering is being done so that the insects can be collected in the strainer.

There is no provision for removing the insects if they fit through the sieve and they will then count as dust on the filter. This is not a concern if your results are low, but if the results were to be high then the additional mass of the insects might cause a problem. The density of an insect is lower than mineral dust so the mass contribution should not be significant unless the number of insects is very high. There have been situations where the sample could not be filtered at all because the insects and parts of the insects blocked the filter completely. In these circumstances the samples were discarded but the number of insects was excessive.

It is recommended that you filter as normal and if the insects pass through the sieve then they will be weighed as part of the sample. The MicroScans provided for each sample will be able to see the insects and will also be able to provide an estimate of the mass contribution.

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