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Montana Field Guide

Montana Field Guides

A Millipede - Lophomus laxus

Species of Concern

Global Rank: G1G3
State Rank: S1S3

Agency Status


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General Description
Genus Lophomus: Posterior colpocoxites of male gonopds more complex than simply consisting of long, thin structure partially sheathed at base by sternal process, posterior colpocoxites of male gonopods with an articulated basal flagellum (Shear 1976). Body rather loose-jointed; prozonites very exposed; metazonites flattened between strongly-projecting lateral keels, keels with a pronounced raised rim along posterior margin. Antennae slender with joints decreasing in length as follows: 3, 5, 4, 2, 6, 7, 1. Anterior gonopods of two distinct and greatly different parts. Posterior gonopods 3-jointed, the coxal joint broad, the apical portion broadly elevated and complicated with a long flagellum rising from it front face at base. Sternum broad with its apex narrowly separating the coxal joints. Coxae of male leg 11 with a sharp process distomesally (Loomis and Schmitt 1971).

[From Loomis and Schmitt 1971; Shear 1976] Lophomus laxus: Both sexes to about 13.0 mm length, rather loose-jointed, prozonites somewhat exposed. Body brownish (lighter towards tail), a transverse uncolored spot occupying most of inner area of keel; on back half of body a short colorless area extends along posterior margin between keels, smaller less definite areas elsewhere on dorsum. Ocelli 20-25 in a triangular group of 5-7 series. Antennae long, slender, joints 3, 5, 4, 2, 6, 7, 1 in decreasing order of length, joints 6 and 7 combined about equal to joint 5. Gnathochilarium with a large simple mentum. Prozonites more convex than metazonites and separated from them by a broad deep constriction; metazonites unusually flat between keels (especially in males); dorsal setae long and curved, almost evenly cylindrical to pointed apex. Lateral keels become evident as swellings increasing in size, beginning on segment 2 to 8 or 9, large and prominent to segment 18, then decreasing in size behind segment 18. Anterior gonopods of two distinct elements and a large sternum. Posterior gonopods with long slender telopodite rising from near base of front face of each coxal joint, which is broad, high, ending in 2 widely separated lobes; posterior face with contorted prominence below apex; 2nd joint abruptly clavate. Anterior male legs with knobs proximal on femora 4 and 5. Leg 11 also strongly modified with a large process, slightly sinuous and project from prefemur; coxae of legs 12 and 13 also ventrally pointed.

Limited information. Adults reported late May to mid-October (Loomis and Schmitt 1971; MTNHP collections).

Diagnostic Characteristics
The anterior male legs have knobs proximal on femora 4 and 5, legs 11 also strongly modified with a large slightly sinuous process projecting from the prefemur, similar to Taiyutyla, but the coxae of legs 12 and 13 are also ventrally pointed; posterior gonopods also with an articulated coxal flagellum (Shear 1976).

Range Comments
Endemic to Montana. Documented in Granite, Lake, Missoula, and Ravalli counties, to about 2088 m elevation (Loomis and Schmitt 1971; MTNHP collections).

Summary of Observations Submitted for Montana
Number of Observations: 10

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Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Coniferous forest: beneath rocks, talus, moss, under canopy including Engelmann spruce, lodgepole pine, subalpine fir, Douglas fir, paper birch, gooseberry, thimbleberry, current (Loomis and Schmitt 1971; MTNHP).

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Citation for data on this website:
A Millipede — Lophomus laxus.  Montana Field Guide.  .  Retrieved on , from