Here are some links that I visit regularly in my natural history work. (Please note that I am not interested in suggestions of other links to include here; these are just some sites that I have personally found useful.)

BugGuide.Net — The general ID Request page is here, and I manage the following pages:

HOSTS – a Database of the World’s Lepidopteran Hostplants – This database is full of misinformation, like the books on which it is based, but it is still a good place to check when looking for a list of suspects when trying to ID a caterpillar on a particular plant.

Lepidopteran Use of Native & Alien Ornamental Plants – A downloadable database that adds to the HOSTS database and makes some corrections to it. It includes an extremely important Literature Cited section, which the HOSTS database does not.

USDA PLANTS Database – Taxonomy is not always up to date, but this site is great for looking at geographic ranges of plants, or getting a list of plants of a particular family or genus found in a given state.

The Biota of North America Program: North American Vascular Flora – Another source for plant distribution data, with nice county maps. – Terry Harrison’s informative and well-illustrated guide to the tiny moths of Illinois.

Imperial Measures of Length – I have to check this page occasionally to remind myself that when 19th century authors talk about “lines,” they’re referring to 2.12 mm increments (12ths of an inch).

The list below is salvaged from my old website.  It is somewhat redundant with the list above, and I haven’t gone through it yet to weed out broken links, but it may still contain some useful things.
Catalogue of Life
Integrated Taxonomic Information System
World Register of Marine Species
Discover Life


What’s That Bug?
Nomina Insecta Nearctica
Nomina Circumscribentia Insectorum
Psyche back issues
Journal of Insect Science
British leafminers
Orthoptera Species File
Gordon’s Phasmida Page
Aphid taxonomy
Bibliography of the Neuropterida
The Coleopterists Society
Tiger Beetles of the United States
Bark and Wood Boring Beetles of the World
Hymenoptera Name Server
Electronic World Catalog of Symphyta
Cynipid taxonomy
Identification Atlas of the Vespidae of the northeastern Nearctic region
Trichoptera World Checklist
The Global Lepidoptera Names Index
Butterflies and Moths of North America
Digital Guide to Moth Identification
HOSTS: A Database of the World’s Lepidopteran Hostplants
The World Spider Catalog
American Arachnological Society
International Society for Arachnology
Checklists of U.S. Scorpions
World Checklist of Millipede Groups
Land Snails and Slugs of the Mid-Atlantic and Northeastern United States


Tadpoles of the United States and Canada: A Tutorial and Key
Tadpole Identification Table


Images, identification, and ecological information

Flora of North America
Key to Carex Sect. Ovales East of the Rocky Mountains (Flora of North America)
Silvics of North America
Orchids of the United States
Coniferous forest bryophytes
Current IPANE species list (Invasive Plant Atlas of New England)
Massachusetts state-listed noxious weeds (USDA Plants Database)
Massachusetts Prohibited Plants List

Plant uses

Plants For A Future
NewCROP search engine
Edible wild plants & mushrooms of New England (Russ Cohen)

Other plant links

Dictionary of botanical epithets
Arthur Haines