Diabrotica biannularis Harold

Species name

Diabrotica biannularis Harold 1875: 91

Type locality

Mexico

Type depository

MNHN, lectotype, female, verified

Diagnosis

Body length 5.5-6.1 mm, width 2.8-3.2 mm. Head basic color black. Antennae filiformfiliform:
slender antennae with antennomeres of similar shape
, bi- or tricolored, antennomeres 1-3 yellow, antennomeres 4-8 gradually infuscated, antennomeres 9 - 10 yellow ocher, antennomereantennomere:
"segment" of antenna, more or less clearly separated
11 dark apically. Antennomereantennomere:
"segment" of antenna, more or less clearly separated
3 less than 1.5 times longer than antennomereantennomere:
"segment" of antenna, more or less clearly separated
2, male antennae length exceeds two thirds of elytronelytron:
<em>(pl. elytra)</em> the fore highly sclerotized wing of beetle
. Maxillary palpi and labrumlabrum:
the "upper lip" of beetles, a movable sclerite joined under clypeus
black or piceous. Pronotumpronotum:
the notum of the prothorax with highly sclerotized pronotal disc
yellow or light cadmium, subquadrate, nonfoveate, not shagreened. Scutellumscutellum:
small, usually triangular shield between the bases of elytra
piceous or black. Elytra yellow or rufous, with three black or metallic black blue bandsbands:
(here) transverse maculae on the beetle elytra
, basalbasal:
of or pertaining to the base, as in the first, or basal segment of an appendage; opposite of apical
and middle bandsbands:
(here) transverse maculae on the beetle elytra
connected together so two yellow maculae bounded on elytral basis. Posteriorposterior:
the region of the body parts of the beetle furthest from the head
band on each elytronelytron:
<em>(pl. elytra)</em> the fore highly sclerotized wing of beetle
ring-shaped (sometimes opened). Epipleura completely yellow, sutural anglesutural angle:
the posterior angle or apex of the elytron near the suture
of elytronelytron:
<em>(pl. elytra)</em> the fore highly sclerotized wing of beetle
round, punctation dense, fine. Abdomen yellow. Legs yellow. Aedeagusaedeagus:
the main sclerotized part of the male genitalia; "aedeagus" is used here instead of "median lobe of aedeagus"
symmetric, with four internal sac scleritessclerites:
(here) the sclerotized hooks, spines or plates in the internal sac
.

Known distribution

Mexico, Belize, Honduras, Guatemala, Costa Rica, Panama

Host plants

Unknown

Remarks

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: scutellumscutellum:
small, usually triangular shield between the bases of elytra
of D. biannularis is black, but yellow in D. bioculata, D. pulchella and D. godmani. The shape of the internal sac scleritessclerites:
(here) the sclerotized hooks, spines or plates in the internal sac
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 elytronelytron:
<em>(pl. elytra)</em> the fore highly sclerotized wing of beetle
length, in D. chontalensis female antennae exceed two thirds of elytronelytron:
<em>(pl. elytra)</em> the fore highly sclerotized wing of beetle
length. Antennae in D. biannularis are thinner than in D. chontalensis. There is no difference in the internal sac armament of the aedeagusaedeagus:
the main sclerotized part of the male genitalia; "aedeagus" is used here instead of "median lobe of 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 antennomereantennomere:
"segment" of antenna, more or less clearly separated
3 is only slightly longer than 2 in D. spilota, however length may vary between specimens. Sclerite 4C in the internal sac of aedeagusaedeagus:
the main sclerotized part of the male genitalia; "aedeagus" is used here instead of "median lobe 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.