Numbers
Ten species in North America:
Chilocorus cacti (Linnaeus, 1767)
Chilocurus circumdatus (Gyllenhall in Schönherr, 1808)
Chilocorus hexacyclus Smith, 1959
Chilocorus tricyclus Smith, 1959
Chilocorus tumidus Leng, 1908
Identification
If possible, look at the beetle's underside. Some species of Chilocorus are externally inseparable except for the underside, so flip the beetle over if you can!
Using Gordon's ref.
(1), here's a simplified ID tree based on distribution and external characteristics:
1) C. stigma - entire US east of Sierra Nevada mountains; Canada east of Rockies. Elytra spots appear to be much larger in southern part of range. Venter (around legs) mostly black, only abdomen red or yellow.
Exceptions within C. stigma's range:
2) C. cacti - Southern Arizona, CA, TX, and FL - Large elytra spots as with southern C. stigma. Venter mostly red or yellow. Only prosternum black.
3) C. tumidus - mid-Atlantic states - Elytra spots somewhat transverse (wider than they are long). Venter like C. cacti.
4) C. hexacyclus - Alberta, eastern slope of Rockies - inseparable from C. stigma
5) C. kuwanae - Introduced throughout much of US from Japan/Korea, then known as C. similis var. japonicus. Spots on elytra are located at middle or slightly behind middle, and are more rectangular rather than circular. Lateral margin of elytra strongly flared. Venter like C. stigma.
6) C. circumdatus - Introduced to Florida. Dorsal pattern unlike any other North American Chilocorus: orange to light red with no markings.
West coast Chilocorus:
7) C. orbus - probably west coast US, CA to Wash., not reaching Canada. Venter like C. stigma
8) C. fraternus - probably same distribution as C. orbus. Externally inseparable from C. orbus.
9) C. tricyclus - probably British Columbia. Externally inseparable from C. orbus.
10) C. bipustulatus - Introduced to CA, possibly elsewhere. Dorsal pattern unlike any other Chilocorus: reddish-brown with transverse band of six partially-connected spots.
Range
See under Identification above
Habitat
Arboreal (in trees) where scale insects are found.
See Also
Hyperaspis spp. - Several Hyperaspis can have the "black with two red spots" pattern:
.
The antennae of Hyperaspis are thin and have a slight club at the end. Chilocorus has short, stout, pointed antennae. Chilocorus individuals normally have a bit of flattened margin around the lateral elytral edge, specially toward the shoulders. They also can appear slightly pointed posteriorly, and/or appear to be more of an A-frame, than evenly convex as in Hyperaspis. Some Hyperaspis are easily identified by white markings on the head or front and lateral margins of the pronotum, but the all-black ones are more challenging.
Calvia quatuordecimguttata, dark form - again the lateral edge shape shows that this is not Chilocorus. Spots are also usually a little flattened apically, with a bit of a jagged edge and sometimes a little pink. Venter with red and black on abdomen.
Ashy-Gray Lady Beetle (Olla v-nigrum), dark form - easily distinguished by the white pronotum. Spots shaped like a triangle or half-moon, sloped toward the rear.
Axion plagiatum - throughout the southern and midwestern US. It is a member of tribe Chilocorini, closely related to Chilocorus, with the same shape and profile. Unlike all Chilocorus, it has black abdominal segments.
