When we speak of overall insect decline, it appears to be across the board.

Note that there are different methods for assessment besides the
windshield.  Night-trapping is one, but applies only to nocturnal flying
insects--largely moths and beetles.  Light pollution due to humans may be a
large factor.

Another source are the flying adult stages of aquatic insects, noted for
their huge populations.  A recent article in the Guardian discusses the
study
https://www.sciencedirect.com/science/article/pii/S0269749117329792?via%3Dihub

"The new research looked at the blue-winged olive, a common mayfly present
across the British Isles and most of continental Europe. Its numbers have
fallen significantly in recent decades and it has almost vanished from some
English rivers...
The prime suspects for this decline are fine sediment and phosphate
pollution in rivers, which are washed off farmed fields and also result
from untreated sewage."

I've performed a fair amount of benthic macroinvertebrate sampling of
streams, and have clearly observed the profound effects of pollution upon
sensitive species.  The question then, is whether specific pesticides are
involved.  Perhaps the best database is in the Netherlands, from which we
might gain some insight.

The only study that I know of is  Van Dijk TC, Van Staalduinen MA, Van der
Sluijs JP (2013) Macro-Invertebrate Decline in Surface Water Polluted with
Imidacloprid. PLoS ONE 8(5): e62374. doi:10.1371/journal.pone.0062374

Unfortunately, the study was funded by an anti-neonic group, so the data
was cherry-picked so as to draw the bullseye around the arrow.  I'd really
like to see a complete analysis of that valuable data set--one that looked
for correlations between each the many pesticide residues measured, and the
prevalence of different species of invertebrates.
-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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