The social millipede Brachycybe lecontii. A. Several B. lecontii individuals atop a piece of decaying hickory wood from their habitat (Shortt Gap, Tazewell County, Virginia); B. Female B. lecontii, scanning electron micrograph (SEM) of the ventral surface of rings 1–14; C. Male B. lecontii, SEM of the ventral surface of rings 1–13. Scale bars B, C = 1 mm.

Distribution of Brachycybe lecontii. Brachycybe lecontii has a large, fragmented distribution (in blue), extending from southern Missouri and West Virginia to eastern Texas and southern Georgia.

Early developmental stages of Brachycybe lecontii. A. Egg of B. lecontii, aside from some wrinkles due to desiccation, the egg surface is smooth (note: base of egg circled with ring of carbon paste); B. A hatching B. lecontii with five leg pairs and seven body rings, the amber oval object in the foreground is the empty egg shell; C. Stadium I B. lecontii, ventral; D. The same, left ventrolateral view. Scale bar A = 0.4 mm; scale bar C, D = 0.5 mm.

Development of Brachycybe lecontii. (Left) Illustration of a stadium I B. lecontii. (Right) Numbers of rings and legs observed in each developmental stage (stadia I–VII), VII+ denotes either stadia VII or VIII; top half of circle = number of rings; bottom half of circle = leg number (white, n = 1; red, n = 2–5; blue, n = 50).

Scanning electron micrographs of stadium I, II and adult Brachycybe lecontii individuals, ventral view. A. Stadium I individual; B. Stadium II individual with coxal sacs (cs) visible; C. Stadium II individual; D. Adult male individual; E. Stadium I individual with two-leg pair rudiments (lpr) visible between pleurotergites (pt); F. Adult with three-leg pair rudiments visible between pleurotergites; G. Adult with coxal sacs on legs showing bivalve covering, left coxal sac expanded. Median sternal process (sp) visible between leg coxae. Scale bar A–C = 0.5 mm; scale bar D = 1.0 mm; scale bar E = 0.1 mm; scale bar F, G = 0.25 mm. Abbreviations: cs, coxal sacs; lpr, leg-pair rudiments; pt, pleurotergites; sp, sternal process.

Paternal care in Brachycybe lecontii, males with clutches of eggs. A. Male curled around eggs with an aggregation of hatchlings near their natal site (arrow, one unhatched egg next to empty egg shells), from Gillam Park, Little Rock, Pulaski County, Arkansas; B. Male carrying eggs; C. Male curled around eggs. (B and C from Mount Kessler, Fayetteville, Washington County, Arkansas); D. Male curled around eggs from Campbell County, Tennessee (photo by Matt Berger).

Chemical defence glands of Brachycybe leconti. A. Ventral view of the paranotum of a live B. lecontii (BLIV0080) that shows the vase-shaped defence gland (arrows) with bubbles of defensive secretion visible within the gland; B. Anterior view of live B. lecontii (BLIV0080), head bent downwards, which shows the large vase-shaped defence gland that is visibly white in colour and indicated by an arrow; C. Illustration (dorsal view) of the right paranotum of a B. lecontii individual.

Pinwheel aggregations of Brachycybe lecontii millipedes with fungus. A. Millipedes with unidentified phlebioid polypore (top of frame) from Arkansas; B. Pinwheel of millipedes from Dickson County, Tennessee; C. Stadium I millipedes with unidentified fungus from Campbell County, Tennessee (photo by Matt Berger); D. Millipedes with unidentified fungus from Mount Kessler, Fayetteville, Washington County, Arkansas; E. Millipedes with unidentified fungus from Issaqueena Falls, Oconee County, South Carolina.

Brachycybe lecontii with fungus. A. Lateral view of head and first 10 rings of B. lecontii with fungus; B. Anterior view of the head and first 8 rings of same individual as above with fungus.

Evidence of fungal feeding in Brachycybe lecontii. A. Millipedes with unidentified fungus from Issaqueena Falls, Oconee County, South Carolina; B. Same after 15 minutes with evidence of fungal feeding from a pit (feeding bowl) in the surface of the fungus (inset, magnified view); C. Feeding bowl, arrow and impression of the anterior section of the millipede trunk (impression outlined in black dotted line, inset); D. Magnified view of A, showing two millipedes with their heads immersed in gelatinous fungal tissue, arrows and curved dotted lines showing fungus that is bulging out of the feeding bowl; E. Several feeding bowls in fungus, arrows; F. Millipedes with feeding bowl, arrow, in fungus from Montgomery Bell State Park, Dickson County, Tennessee (feeding bowl impression, inset).

Mandibles and other mouthparts of Brachycybe lecontii. A. Ventral view of mandibles (md) and buccal cavity of B. lecontii, gnathochilarium removed; B. Gnathochilarium of B. lecontii, dorsal view of dissected gnathochilarium; C. Ventral view of mandibles, gnathochilarium removed; D. Ventral view of epipharyngeal cleft (epi), gnathochilarium removed. Scale bar A, B = 0.1 mm; scale bar C = 50 μm; scale bar D = 5 μm. Abbreviations: epi, epipharyngeal cleft; ge, genae of head; md, mandible gnathal lobe; gg, genal groove; gr, gnathochilarial ridge.

Labrum of Brachycybe lecontii. A. Fibrous brush-like labrum and gnathochilarium of an adult B. lecontii; B. The same of a juvenile B. lecontii; C. Magnified view of the labrum in A; D. Magnified view of the labrum in B. Scale bar A, B = 50 μm; scale bar C, D = 20 μm. Abbreviations: lbu, labral brush; lbr, labrum; ll, laminae linguales; lr, labral ridge; m, mentum; s, stipes.

Composition of social pinwheel aggregations of Brachycybe lecontii, according to sex and life stage. A. Composition of pinwheels by sex; B. Composition of pinwheels by sex and life stage. BLCV numbers correspond to individual pinwheels.

Scanning electron micrographs of combs present on the tarsus of Brachycybe lecontii (anterior view). A. Tarsus of adult B. lecontii with comb-like structures; B. Magnified view of tarsal comb; C. Magnified view of tarsal claw. Scale bar A = 0.1 mm; scale bar B, C = 20 μm. Abbreviations: as, accessory seta; ta, tarsus; tc, tarsal comb; ti, tibia.

Illustrations of tarsal combs of Brachycybe lecontii (anterior view). A. Comb on second leg of an adult B. lecontii; B. Comb on the first leg of a stadium I B. lecontii. Abbreviations: as, accessory seta; ta, tarsus; tc, tarsal comb; ti, tibia.

Reflectance spectra of the cuticle of Brachycybe lecontii. Reflectance (%) measured in 18 live millipedes. The y-axis is percent reflectance and x-axis is wavelength of light in nanometres (nm). The plot includes a median (red line) and standard deviation (light red area above and below the line).