Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 10 (9)

A Neonicotinoid Insecticide at a Rate Found in Nectar Reduces Longevity but Not Oogenesis in Monarch Butterflies, Danaus plexippus (L.). (Lepidoptera: Nymphalidae)


A Neonicotinoid Insecticide at a Rate Found in Nectar Reduces Longevity but Not Oogenesis in Monarch Butterflies, Danaus plexippus (L.). (Lepidoptera: Nymphalidae)

David G James. Insects.


The monarch butterfly in North America has suffered a serious population decline since the mid-1990s. The introduction and widespread use of neonicotinoid insecticides during the same time period has been suggested as a potential driver of this decline but no studies have looked at the impact of these insecticides on adult monarchs. A brief laboratory study assessed the impact of Imidacloprid, the most commonly used neonicotinoid, on western monarch butterfly longevity and oogenesis. Imidacloprid at 23.5 ppb, a field-realistic rate reported from wild nectar and pollen, was fed ad libitum to newly-eclosed monarchs in a sugar-based diet for 22 days. Treated monarchs showed reduced longevity, suffering 78.8% mortality by day 22, compared to 20% in untreated monarchs. Prior to death, butterflies exhibited signs of poisoning including uncoordinated flapping of wings and uncontrolled vibrating of wings and body. Imidacloprid did not reduce egg production. Shortened adult longevity has serious consequences for monarch population development, migration and overwintering. The potential widespread impact of imidacloprid-contaminated crop and wild flower nectar, may be a significant driver of monarch population decline. More research on the impact of neonicotinoid insecticides on the monarch and other butterflies should be viewed as a serious priority.

Keywords: adult monarch butterfly; imidacloprid; monarch butterfly decline; neonicotinoids; survival.

Conflict of interest statement

The author declares no conflict of interest.


Figure 1
Figure 1
Mortality of caged monarch butterflies fed sugar water alone or sugar water containing 23.5 ppb imidacloprid during three weeks post-eclosion.

Similar articles

See all similar articles


    1. Brower L.P., Taylor O.R., Williams E.H., Slayback D.A., Zubieta R.R., Ramirez R.R. Decline of monarch butterflies overwintering in Mexico: Is the migratory phenomenon at risk? Insect Conserv. Divers. 2012;5:95–100. doi: 10.1111/j.1752-4598.2011.00142.x. - DOI
    1. Semmens B.X., Semmens D.J., Thogmartin W.E., Wiederholt R., Lopez-Hoffman L., Diffendorfer J.E., Pleasants J.M., Oberhauser K.M., Yatlor O.R. Quasi-extinction risk and population targets for the eastern migratory population of monarch butterflies (Danaus plexippus) Sci. Rep. 2016;6:23265. doi: 10.1038/srep23265. - DOI - PMC - PubMed
    1. Stenoien C., Nail K.R., Zalucki J.M., Parry H., Oberhauser K.S., Zalucki M.P. Monarchs in decline: A collateral landscape-level effect of modern agriculture. Insect Sci. 2016 doi: 10.1111/1744-7917.12404. - DOI - PubMed
    1. Marini L., Zalucki M.P. Density dependence in the declining population of the monarch butterfly. Sci. Rep. 2017;7:13957. doi: 10.1038/s41598-017-14510-w. - DOI - PMC - PubMed
    1. Pleasants J.M., Zalucki M.P., Oberhauser K.S., Brower L.P., Taylor O.R., Thogmartin W.E. Interpreting surveys to estimate the size of the monarch butterfly population: Pitfalls and prospects. PLoS ONE. 2017;12:e0181245 doi: 10.1371/journal.pone.0181245. - DOI - PMC - PubMed