I can't help myself, I've just got to post this!  I think they have already begun a sensus.  Check out the last couple of paragraphs.

Whether you're talking about a swarm of bees buzzing about, a cluster of butterflies sucking down nectar or a nest of cockroaches hidden in a corner of your house, insects are plentiful. Really plentiful.
Scientifically speaking, the term "insect" denotes a member of the class Insecta. For brevity's sake, if you have a head, a thorax, an abdomen, three sets of legs protruding from your body and often a pair or two of wings, perhaps for making a quick getaway, then you're most likely an insect. So how many are there?
It seems like an impossible question for good reason: We don't even know how many different insect species there are, which makes it difficult to perform an all-inclusive worldwide insect census, according to David Hogg, an entomology professor at University of Wisconsin-Madison specializing in population ecology and pest management.
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Add to that monumental task the often brief life span of an insect, such as the adult mayfly -- a mere 24 hours -- and you'd have some serious difficulty physically counting all the insects filling the planet's air at any given moment [source: Turpin]. If you were really interested in this endeavor, you might have more luck counting insect queens of the ant, termite and bee varieties, which may rule their colonies for years. In fact, a termite queen may reign for as long as half a century [source: Turpin].
Of course, entomologists are interested in more than just the ruling class of the insect world, so they've devised automated and old-fashioned ways to survey, count and classify insects present in a select area.
One novel technique for measuring biodiversity may surprise you: A group of scientists sought to find out how many different species of insects inhabited two different regions. To collect the raw data, they used the front bumper of a moving vehicle and the open road. The resulting bug splatter on the bumper contained a treasure trove of genetic evidence from the various insects that struck it. The scientists then sequenced the DNA samples from the splatter and compared it with existing sequence databases for insects [source: Calicchia].
The method isn't perfect, but it does attempt to classify, if not quantify, those buzzing masses.