Scientists & Staff

Nathan Havill

Nathan P. Havill

Research Entomologist
51 Mill Pond Rd.
Hamden, CT, 06514
Phone: 203-230-4320

Contact Nathan P. Havill

Current Research

With expertise in the ecology and evolution of multi-trophic interactions, I work to provide information about invasive pests, their natural enemies, and the impacted trees. Understanding the interactions among these trophic levels is critical to making sound management decisions to reduce the impact of forest pests. Facets of my research include investigating: 1) systematics and population genetics of invasive pests, especially hemlock woolly adelgid, balsam woolly adelgid, gypsy moth, southern pine beetle, and winter moth; 2) systematics and population genetics of predators and parasitoids being evaluated as biological control agents of invasive species, especially of hemlock woolly adelgid; 3) hybridization between native and non-native species; 4) predicting the impact of non-native species using phylogenies; and 3) systematics and biogeography of North American tree species and their relatives.


My goal is to help reconstruct the evolutionary history of multiple trophic levels of a pest system to guide management and mitigate the impact of insect pests on forested ecosystems of the northeastern United States. I am especially concerned with research related to classical biological control to develop practical, cost effective tools used to evaluate the safety and efficacy of predators or parasites introduced as biological control agents.

Why This Research is Important

Invasive insects in North America are not often pests in their region of origin due to resistant tree species and natural enemies that co-evolved with the pest over millions of years. Insect becomes pests following introduction outside their native ranges when these bottom-up and/or top-down regulating factors are no long effective. The hemlock woolly adelgid, Adelges tsugae (Adelgidae), originated in Japan and causes the death and decline of eastern North American hemlock trees in 17 eastern states. The balsam woolly adelgid, Adelges piceae (Adelgidae), originated in Europe and has been killing fir trees throughout North America for over 100 years. The gypsy moth, Lymantria dispar (Lymantriidae), also was also introduced from Europe over 100 years ago. It is controlled to some extent by a pathogenic fungus in areas where it is well established, so management in the U. S. currently focuses on slowing its spread and on preventing invasion by more virulent strains from Asia. The winter moth, Operophtera brumata (Geometridae), is also from Europe and defoliates a broad range of tree species, including oaks and birches in southern New England, and is hybridizing with the native Bruce spanworm, O. bruceata. Together, these pest species represent a diverse group of insects with very different feeding strategies, life cycles, host ranges, and natural enemy complexes.


  • Yale University, Ph.D. Ecology & Evolutionary Biology, 2006
  • Yale University, M.S. Ecology & Evolutionary Biology, 2003
  • University of Wisconsin, Madison, M.S. Entomology, 1998
  • College of William and Mary, B.S. Biology, 1996

Professional Organizations

  • Society for the Study of Evolution (2012 - Current)
  • Connecticut Entomological Society (2001 - Current)
  • Entomological Society of America (1996 - Current)

Featured Publications & Products

Publications & Products

Research Datasets

  • Havill, Nathan P. 2019. Microsatellite genotypes for southern pine beetles, Dendroctonus frontalis, from the U.S. and Mexico. Fort Collins, CO: Forest Service Research Data Archive.

National Research Highlights

Red pines (Pinus resinosa) killed by the red pine scale (Matsucoccus matsumurae) near Myles Standish State Forest, Massachusetts. Photo by Jeff Garnas[MOU1] , University of New Hampshire.

A Tree Species’ Evolutionary History Predicts Impact of Invasive Pests

Year: 2020

Research by Northern Research Station scientists and their partners presents the first evidence supporting a long-held hypothesis that a tree’s evolutionary history is key to its susceptibility to nonnative herbivorous insects. This discovery has the potential to be a game-changer in predicting the impact of and managing nonnative insects.

A silver fly on eastern hemlock infested with hemlock woolly adelgid.

Silver flies show promise as potential biological controls of hemlock woolly adelgid

Year: 2017

Forest Service science is identifying potential biological control of hemlock wooly adelgid, an invasive insect that is devastating hemlock trees in the Northeast. Two species of silver flies from the Pacific Northwest are showing promise as potential biological controls of hemlock woolly adelgid in the East. The research has demonstrated that these predators can feed and develop on hemlock pest adelgids in the eastern U.S., and they are able to tolerate environmental conditions at the southern and northern ends of the area invaded by the Japanese adelgids. Efforts are underway to release these flies so they will establish in the eastern U.S. and evaluate their ability to control this invasive pest.

Winter moths attracted to a porch light during an outbreak in Manomet, MA. Jeff Boettner, University of Massachusetts.

Non-native Insect Hybridization Provides Opportunity for Research

Year: 2016

A recent outbreak in New England of the non-native winter moth from Europe provides an unprecedented opportunity to examine the effects of hybridization because Forest Service scientists discovered that it is hybridizing with the native Bruce spanworm. They developed two new sets of genetic markers that confirmed the presence of multi-generation asymmetric hybridization.

Vial of silver flies ready for field release. USDA Forest Service

First Release of a New Biological Control of Hemlock Woolly Adelgid

Year: 2015

Forest Service scientists and their research partners tested and released two species of silver flies from the western United States for biological control of hemlock woolly adelgid in Tennessee and New York.

Last modified: Tuesday, July 5, 2022