Diabrotica biannularis Harold 1875: 91
MNHN, lectotype, female, verified
Body length 5.5-6.1 mm, width 2.8-3.2 mm. Head basic color black. Antennae filiform, bi- or tricolored, antennomeres 1-3 yellow, antennomeres 4-8 gradually infuscated, antennomeres 9 - 10 yellow ocher, antennomere 11 dark apically. Antennomere 3 less than 1.5 times longer than antennomere 2, male antennae length exceeds two thirds of elytron. Maxillary palpi and labrum black or piceous. Pronotum yellow or light cadmium, subquadrate, nonfoveate, not shagreened. Scutellum piceous or black. Elytra yellow or rufous, with three black or metallic black blue bands, basal and middle bands connected together so two yellow maculae bounded on elytral basis. Posterior band on each elytron ring-shaped (sometimes opened). Epipleura completely yellow, sutural angle of elytron round, punctation dense, fine. Abdomen yellow. Legs yellow. Aedeagus symmetric, with four internal sac sclerites.
Mexico, Belize, Honduras, Guatemala, Costa Rica, Panama
Smith and Lawrence (1967) designated the lectotype of D. biannularis, a female in the Allard collection in the MNHN. Three additional specimens from the Allard collection bear about the same pale blue handwritten label: "Mexico". They are identical with the type female in the coloration and one of them is a male. We consider them paralectotypes of D. biannularis. Smith and Lawrence (1967) indicated: "Three additional examples in the ZMB [MfN] are possible paralectotypes." We studied these specimens. One male bears labels: "biannularis" [white handwritten], "Xalappo Deppe" [bluish-green handwritten], "30959" [white printed] and 'Keine Typus Smith 1964' [pink, printed with handwritten notes]; it definitely belongs to the original Harold's series and therefore is a paralectotype of D. biannularis. Its genitalia are identical with the genitalia of male from the MNHN. It supports our species concept of D. biannularis.
Potential problems with identification
Diabrotica biannularis is very similar to many of the "oculate" species such as D. gratiosa Baly, D. adelpha Harold, D. bioculata Bowditch, D. pulchella (Jacquelin-du-Val) and D. godmani Jacoby. They can be separated by the following features: scutellum of D. biannularis is black, but yellow in D. bioculata, D. pulchella and D. godmani. The shape of the internal sac sclerites allows to distinguish D. biannularis from all other species too. Sclerite 4A is an elongate spine. Sclerite 4C is quite remarkable; it is a thick, bent, and pointed hook bearing 4-6 big teeth apically.
Diabrotica biannularis is particularly similar to D. chontalensis Jacoby and D. spilota Baly. The only feature allowing to distinguish D. biannularis and D. chontalensis is female antennal length. Female antennae are very short in D. biannularis, do not exceed a half of elytron length, in D. chontalensis female antennae exceed two thirds of elytron length. Antennae in D. biannularis are thinner than in D. chontalensis. There is no difference in the internal sac armament of the aedeagus in both species. According to Jacoby (1887) the only feature allowing to distinguish D. chontalensis is "very short second and third joints of the antennae, these joints being of exactly the same length". The antennomeres 2 and 3 are about the same lenght in D. biannularis and D. chontalensis. The antennomere 3 is only slightly longer than 2 in D. spilota, however length may vary between specimens. Sclerite 4C in the internal sac of aedeagus is slightly longer and slender in D. spilota than in D. biannularis and D. chontalensis. D. spilota is slightly larger than D. biannularis and D. chontalensis. It is possible that all three names belong to the same species. Jacoby (1887) noted about D. spilota: "there are, however, varieties before me in which the spots of the elytra are either transversely or longitudinally connected". Thus D. spilota is most likely an example of an extreme pattern reduction in D. biannularis. Finally, Baly (1886) gave Mexico as a locality for D. spilota. Smith and Lawrence (1967) wrote that "It is possible that the Mexico record given by Baly is a misinterpretation of a [Magd] handwritten label". It seems that Mexico record was true and D. spilota range may be from Mexico to South America.