Bidens tripartite
- Photograph, systematic position, morphology, biology, distribution, ecology and economic significance of Spanish Needles.
- http://www.agroatlas.spb.ru/weeds/Bidens_tripartita_en.htm

A Close-up View of Four Beggar-ticks
- Photographic study by Brian Johnston of four species of Bidens with many fine images, both macroscopic and microscopic.
- http://www.microscopy-uk.org.uk/mag/artaug05/bjbticks.html

Bidens frondosus
- Images, specimen location map, list of habitats, and links to further information.
- http://www.botany.wisc.edu/wisflora/scripts/detail.asp?SpCode=BIDFRO

Bidens aristosa
- Bearded Beggarticks.
- http://plants.usda.gov/java/profile?symbol=BIAR

Bidens frondosa
- Devil's Beggartick.
- http://plants.usda.gov/java/profile?symbol=BIFR

Bidens cernua
- Nodding Beggartick.
- http://plants.usda.gov/java/profile?symbol=BICE

Bidens tripartita
- Threelobe Beggarticks.
- http://plants.usda.gov/java/profile?symbol=BITR

Bidens discoidea
- Small Beggarticks.
- http://plants.usda.gov/java/profile?symbol=BIDI

Bidens laevis
- Smooth Beggartick.
- http://plants.usda.gov/java/profile?symbol=BILA

Bidens coronata
- Crowned Beggarticks.
- http://plants.usda.gov/java/profile?symbol=BICO

Bidens connata
- Purplestem Beggarticks.
- http://plants.usda.gov/java/profile?symbol=BICO5

Bidens mitis
- Smallfruit Beggarticks.
- http://plants.usda.gov/java/profile?symbol=BIMI

Bidens pilosa
- Images, description, and invasiveness.
- http://www.hear.org/pier/bipil.htm

Bidens alba
- Romerillo.
- http://2bnthewild.com/plants/H402.htm

Bidens amplectens
- image
- http://www.botany.hawaii.edu/faculty/carr/images/bid_amp.jpg