J. F. Lawrence and K. Stephan.
The North American Cerylonidae (Coleoptera: Clavicornia).
Psyche 82:131-166, 1975.

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PSYCHE
Vol. 82 June, 1975 No. 2
THE NORTH AMERICAN CERYLONIDAE
(COLEOPTERA: CLAVICORNIA)
BY JOHN F. LAWRENCE~ AND KARL STEPHAN~
The Cerylonidae are a family of small to minute beetles (usually 2 mm. 01- less) which occur most commonly in forest litter and under bark. At present, there are about 40 genera and over 300 described species known from all of the major zoogeographic regions. Crowson (1955) first recognized the Cerylonidae as an independent clavicorn family, including the cerylonines and murmidiines, as well as Euxes- tus and its allies; but these groups have been treated as tribes of the heteromerous family Colydiidae by both Hetschko (1930) and Ar- nett (1968). In their world generic revision of the family, Sen Gupta and 'Crowson (1973) added Anommatus Wesmael, Abromus Reitter, and Ostomopsis Scott, while transferring Eidoreus Sharp (== Eupsilob'ws Casey) to the Endomychidae. The present paper consists of a revision of the 10 genera and 18 species of Cerylonidae occurring in America north of Mexico. With respect to the compo- sition of the family and that of its major subordinate groups, we have followed the classification presented by Sen Gupta and Crowson; the interrelationships among the subgroups, however, are still obscure, so we have treated the Euxestinae, Anommatinae, Metaceqloninae (not North American), Murrnidiinae, Ostomopsinae, and Cerylon- inae as independent subfamilies.
The following abbreviations have been used in keys and descrip- tions: PL - pronotal length, PW - pronotal width, EL - elytral length, EW - elytral width, and TL -sum of PL and EL. The word "length" refers to the total length, including the head, and is 'Published with the aid of a grant from the Museum of Comparative Zoology.
Museum of comparative Zoology, Harvard University, Cambridge, Mass.
%03S E. Eastland St., Tucson, Ariz.
Manuscript received by the editor July 6, 1975.



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not equivalent to TL. The word "ventrite" has been used for each of the five visible abdominal sternites; thus the first and last ventrite refer to abdominal sternites three and seven, respectively. Descrip- tions of pronotal and elytral punctation should be used with caution, since the apparent diameters of punctures may vary considerably with the angle of light.
A complete family definition and comparisons with related or similar groups have been provided by Sen Gupta and Crowson ( 1973). A brief summary will be given here. Adult Cerylonidae
may be characterized as follows : I ) antennal insertions exposed ; 2) antennal club compact, rarely with more than 2 segments; 3) corporotentorium with median anterior process ; 4) procoxae small and rounded, with concealed lateral extensions; 5) mesocoxal cavi- ties broadly closed outwardly by the sterna and joined by a straight line; 6) trochanters not or only weakly heteromeroid (obliquely attached to femur) ; 7) tarsal formula 4-4-4 (or rarely 3-3-3), the segments simple (or rarely the first lobed), with simple claws; 8) hindwing without a closed radial cell and with one anal vein, or with the first anal running into the subcubital fleck; 9) abdominal ventrites .free, the first distinctly longer than the second; 10) aedea- gus of the clavicorn type, lying on its side when retracted, often with a reduced tegmen. In addition, the majority of cerylonids are glabrous, and many have reduced antennal segmentation, aciculate maxillary palps, femoral lines, and a crenulate hind margin on the last ventrite.
Several of the above characters are shared with other families of the cerylonid series (Crowson, 1955), namely, the Sphaerosomatidae, Endomychidae, Coccinellidae, Corylophidae, Discolomidae, Mero- physiidae, and Lathridiidae. The broadly closed middle coxal cavi- ties, characteristic tentorium, more or less compact antenna1 club rarely more than 2-segmented, and simple tarsi will distinguish the cerylonids from most of the above groups. 'Corylophids have similarly closed mesocoxal cavities, but the tentorium is reduced, the antennal club is 3-segmented and relatively loose, and the second tarsal seg- ment is often lobed. Although cerylonids were formerly included in the )family Colydiidae, members of the latter group are easily dis- tinguished by having the basal three or four ventrites connate, the aedeagus of th'e pseudotrilobe type, and the trochanters strongly heteromeroid or the antennal insertions concealed. Cerylonid larvae are elongate or oval in shape, without or with weakly developed frontal sutures, and with o, 2, or 3 ocelli on each side of head. The antennae are relatively short, with the sensory



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19751 Lawrence ‰â Stephan - Cerylonidae 133 appendix longer than the terminal segment, the tarsungulus bears a single seta, and the spiracles are annular. In the more generalized forms, such as Anommatus, Murmidius, and the Euxes.tinae, the head is prognathous or somewhat inclined, and the mouthparts are of the normal clavicorn type, with a chewing, mola-bearing mandible and a short, blunt mala. In the Ceryloninae, however, the head is strongly hypognathous or opisthognathous, and the mouthparts form a highly modified piercing apparatus, in which both mandible and the mala are elongate and blade-like.
The flat, onisciform larvae of Murmidius ovalis (see Boving and Craighead, 1931 ; Halstead, 1968; Sen Gupta and Crowson, 1973) resemble those of the Discolomidae and certain Corylophida,e. Dis- colomid larvae, however, have only 2-segmented maxillary palps, those of the Corylophidae have the labrum and clypeus fused, and both lack the characteristic bundles of long, barbed setae along the sides of the body. The larvae of Euxestus and Hypodacne bear a resemblance to certain Languriidae, especially Cryptophilus, in the form of the tergal processes, surface granulation and setation, and in the single tarsungular claw, but the latter group may be distinguished by the presence of a mandibular prostheca, bicameral spiracles, and 5 or 6 ocelli on each side of the head. Cerylonine larvae are similar in form to some of the smaller Endomychidae, but they are easily recognized by the modified piercing mouthparts. Because of their small size, most cerylonids are collected by mass sampling techniques, and little is known of their food habits or life histories. The most frequented habitats for the group are leaf litter and rotten wood, especially cambium. Species of Cerylon, Philo- thermus, and Mychocerus are usually collected under bark, while those of Lapethus appear to be equally common in leaf litter and forest debris. A number of species have been recorded lfrom ant nests : Hypodacne punctata is known from Camponotus galleries: mag- nathus mirabilis Oke has been associated with Amblyopone in Aus- tralia; and two
species of Lapethus have been collected in large numbers in the refuse deposits of the leaf-cutting ant Atta micana. Elytrotetrantus chappuisi (Jeanne1 and Paulian) is known from a mole-rat nest, while Euxestus erithacus Chevrolat was found breeding in bat guano in a Jamaican cave. Adults and larvae of certain Neo- tropical Philothermus have been taken in polypore fungi, but there were never more than a few individuals. Finally, Murmidius ovalis is known to feed on stored products of man. Almost nothing has been recorded on the actual type of food material taken in by cerylonids. Several gut dissections were made



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Psyche
by one of us, but the particles were often impossible to identify. The larval gut contents of the Euxestus from bat guano contained a variety of hyphal sections and spores, while numerous darkly- pigmented spores of a single type were found in the adult proven- triculus of a Philothermus collected under pine bark in Mexico. The proventriculus of Ceryl'on castaneum collected on dried mushrooms from a tree was filled with sculptured basidiospores, while that of the same species taken under conifer bark contained sections of hyphae, as well as spores. Those forms with piercing-sucking mouth- parts have been assumed to be predators (Besuchet, 1972)) but as yet there is no direct evidence supporting this hypothesis (see below) .
Perhaps the most interesting feature of the subfamily Ceryloninae is the occurrence of piercing-sucking mouthparts in all known larvae and in adults of over 50 species in at least six genera. This condition may have evolved twice in the larval forms and several times in the adults (see below). The most highly specialized type of piercing apparatus in adult cerylonids occurs in the genus Cautomus and has been described and illustrated by Besuchet (1972). In this group,, the labrum-epipharynx and the labium together form an elongate, tubular beak, in which are contained four pairs of stylets, each set consisting of a mandible and its lacinia mandibularis (prostheca), a galea, and a lacinia. The molar area of the mandible is absent, while both the mandibular apex and the prostheca are long and blade-like. The maxillary stylets are extremely long and thin and are attached to a basal fulcrum which allows them to be protracted; the lacinia bears fine recurved teeth and the galea is provided with hairs at the apex. Finally the pharynx is enlarged, forming a pharyngeal pump. This type of condition also occurs in Axiocerylon and its relatives, in the New World Cerylcautonzus, and in a few species of Lapethus. Although the mechanics have not been studied, it is obvious that this represents a piercing-sucking organ similar to those found in various Diptera and Hemiptera.
Besuchet (1972) also discussed the transition from normal chew- ing mouthparts found in Cerylon to those in Cautomus through forms such as Ectomicrus, which exhibit an elongation of the labrum, mandibular apex, galea, and labium. The same type of intermediate condition may be found in species of Lapethus (figs. I 1-12) and in certain Philothermus. In most of these species, the labrum and labium are somewhat elongate, the galea and laciiia are both stylet- like, the mola is usually present, and the mandibular apex retains two



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19751 Lawrence ‰â Stephan - Cerylonidae I3 5 or three small - teeth, which appear to interlock with those of the opposite mandz ble. This type of mandible resembles that found in Collembola, amd it may function in a similar way, with the apical teeth pulling h yphae or strands of wood into the mouth, where they are acted upon by the mola (Folsom, 1899; Macnamara, 1924). The maxillary lobes, although very long and stylet-like, have numerous fine hairs which may serve to gather spores or other particles into the mouth cavity. These mouthparts are somewhat similar to those found in the rhypobiine Corylophidae (Paulian, 1950). In Rhypobws and its relatives, the maxilla has a single stylet, the mandible is divided, with a- basal fulcrum and a long hooked apex, and both are enclosed within the head cavity when not in use. The larvae of cerylonines have two different types of feeding mechanism. In- Philothemus and Lapethus, the labrum and labium form a tubulaa- beak, while the mandible and the mala are both modified into long, blade-like stylets. In addition, the pharynx is enlarged and a pair of salivary glands extend back into the thorax for a distance
equal to the head length. These, like the Cautomus adults, have a well-developed piercing-sucking apparatus. The larval head, however, is strongly hypognathous, and not prognathous like that of the adult. The second type of feeding apparatus is found in the larvae of Cerylon. Here the head is opisthognathous with the labium short and fused to the thorax, and the mandibular and max- illary stylets completely enclosed within the head and apparently attached to a heavily sclerotized internal framework. This condition is remarkably similar to that found in the entognathous apterygote insects, such as the Diplura, Protura, and Collembola (Tuxen, 1959). As mentioned above, the actual food source of these small and uncommon insects is often difficult to ascertain, and this is especially true for those
species ingesting fluids, if this is the case. Although it would be an obvious conclusion that those cerylonids with piercing beaks are predators on small arthropods and nematodes, it is also possible that the beaks penetrate wood or fungal hyphae or that these substances are digested extra-orally. Another possibility is that spores or other objects less that 5 or 6 microns in length are moved into the labral-labial tube by suction or by the action of the setiferous galea; the apical openings of those beaks examined were at least 8 microns wide. Another matter to consider is the normal position of the head. In most of the adults with piercing beaks, the head is somewhat prognathous, so that predation would be possible on active prey species of various sizes. Most cerylonine larvae, however, are



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strongly hypognathous, while that of Cerylon is opisthognathous with entognathous stylets. It is less likely that either larval type would be predaceous. It is hoped that observations on living specimens will provide more information on the feeding habits of both larvae and adults.
The evolution of piercing-sucking mouthparts has occurred at least two more times in the Coleoptera. Leiodid beetles of the genus Myrmech~oleva Lea, which occur with ants in Australia, have a relatively robust, piercing 'beak and prognathous head, and they may be predators on ant larvae. The maxillary stylets are well-developed and blade-like in this group, but the mandibles are much shorter than the beak and do not appear to function as piercing organs. In the family Eucinetidae, members of an undescribed genus from the New World are extremely small (less than I mm.) with a hypognathous head and a labral-labial beak with an opening of about 5 microns; the mandibles in these insects are even further reduced, but the max- illary stylets are very long and fine. A detailed comparison of pierc- ing-sucking feeding mechanisms in beetles will be included in a paper now in preparation by J. F. Lawrence and T. F. Hlavac. We would like to thank those individuals and institutions who made their collections available to us. In the following list abbrevi- ations in brackets are those used in the text: Fred Andrews, Sacra- mento, Calif. [FA] ; California Academy of Sciences, San Francisco, Calif. (D. Cavanaugh, H. B. Leech) PCAS] ; ID. S. Chandler, Columbus, Ohio [DSC]; Henry F. Howden, Ottawa, Canada [HH] ; Field Museum of Natural History, Chicago, 111. (H. S. Dybas) [FM] ; John F. Lawrence, Cambridge, Mass. [JL] ; Mu- seum of Comparative Zoology, Harvard University, Cambridge, Mass. [MCZ] ; Ohio State University, Columbus, Ohio (C. Triple- horn) [,OSU] ; Karl Stephan, Tucson, Arizona [KS] ; Walter Suter, Kenosha, Wisc. [WS] ; William Tyson, Fremont, Calif. LWT] ; University of Arizona (F. G. Werner) [UAZ] ; United ~tatesNationa1 Museum, Smithsonian Institution (J. Kingsolver) [USNM]. The following persons have made a special effort to collect cerylonids and other cryptic beetles and have provided much of the material used in this study: D. Chandler, A. Newton, S. Peck, and W. Suter. We are grateful to R. Crowson, J. Doyen, T. Hlavac, A. Newton and R. Silberglied 'for advice given during portions of this study. We also wish to thank Virginia Phear, Marilyn Pcarce, Jennifer Slade, and Margaret Thayer for typing and proofing, and to F. M. Carpenter for a critical reading of the manuscript.




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19751 Lawrence b' Stephan - Cerylonidae I37 Key t o the Genera of North American Cerylonidae Frontoclypeal suture present; terminal segment of maxillary palp at least 2 X as long as and more than 0.5 X as wide as segment 3, which is shorter th.an or subequal to segment 2 ; last ventrite .................................................... not or very "finely crenulate.
2
Frontoclypea~ suture absent; terminal segment of maxillary palp aciculate, shorter than and less than 0.5 X as wide as segment 3, which is longer than segment 2; apex of la,st ventrite always strongly crenulate (fig. I ) ......................................................... 7 Procoxal cavities closed behind; length at least 2 mm. ; body oval and highly convex, with smooth, even, lateral edges and no antenna1 cavities. ........................................ Hypodacne Le'Conte Procoxal caviti,es open behind; length less than 1.5 mm.; with- ........................................ out other characters in combination, 3
Prothorax without antennal cavities; later,al edges of pronotum crenulate or serrate; metasternurn and first ventrite without femoral lines ; tarsi 3-segmented ; body more elongate, TL/EW more than 1.75. .......................................................................... 4 Proth,orax with antennal cavities; lateral edges of pronotum smooth; rnetasternum and first ventrite with ;femoral lines; tarsi 4-segmented; body round or oval in outhe, TL/EW less than I .75. ...... - ....................................................................................... 5 Lateral margins of pronotum crenulate ; eyes absent ; body elon- gate, TL/EW about 2.5; elytra with 7 rows of punctures bear- ing very short, fine hairs; procoxal cavities very narrowly sep- arated, the intercoxal process depressed and less than 0.2 X a coxal width. ................................................ Anommatus Wesmael Lateral margins of pronotum serrate; eyes present; body oblong, TL/EW less than 2.0; elytra with 10 rows of punctures bear- ing longer, suberect hairs; procoxal cavities more widely sep- arated, the intercoxal process not depressed and at least as wid,e as one coxa. ........................................................ Ostomopsis Scott Antennal cavities of prothorax dorsal, easily visible from above (fig. 21 ) ; antennae 10-segmented ; body strongly convex and elytral punctation seriate. ................................ Murmidius Leach Antennal cavities of prothsorax ventral, not visible from above; antennae with less than 10 segments; body flattened or elytral ..................................................................... punctation confused. 6
Body distinctly flattened ; antennae 9-segmented ; elytral punc- tation seriate; mesosternum truncate anteriorly; metasternal su- ture present. ................................................ Mychocerus Erichson



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138 Psyche [June
Body strongly convex; antennae 8-segmented ; elytral punctation confused ; mesosternum rounded anteriorly ; metasternal suture .absent. .................................................................. Botrodus Casey Prothorax with large, ventral, antennal cavities, situated later- ally and formed primarily .from the hypomera; metasternum and first ventrite with femoral lines; antennae 8-segmented. ............ ............................................................................ Lapethus Casey Prothorax without antennal cavities, or with smaller, mesa1 cavities, formed entirely from the prosternum; metasternum and abdomen without femoral lines; antennae 10- or I I -segmented. 8 Prosternum raised mesially and excavate laterally, forming two shallow antennal caviti,es; labrum acute at apex, beak-like; length less than 1.3 mm.; antennae 10-segmented, with a I-segmented club. ............................ Cerylcautomus Sen Gupta and Crowson Prosternum without antennal cavities; labrum not acute; length more than 1.3 mm. .................................................................... 9 Procoxal cavities open behind or narrowly closed, the postcoxal bridge at apex less than 0.25 X as wide as cavity (fig. 9) ; intercoxal process of prosternum not widened behind ; meso- sternum concave; antennae I I-segmented with a 2-segmented club ; lateral margins of pronotum visible for their entire lengths from above. .................................................... Philothermus Aub6 Procoxal cavities broa,dly closed behind, th,e postcoxal bridge more than 0.5 X as wide as cavity (fig. 10) ; intercoxal process of prosternum strongly widened posteriorly; mesosternum flat or slight1 y convex ; antennae I 0-segmented with I -segmented club; lateral margins of pronotum not visible for their entire lengths from above. .......................................... Cerylon Latreille Euxestinae Grouvelle
As used here, this group is equivalent to the tribe Euxestini de- scribed and delimited by Sen Gupta and Crowson ( 1973), and in- cluding the Cycloxenini and Ta~hyor~ctidiini of Jeanne1 and Paulian (1945). Sen Gupta and Crowson admitted that those characters shared by the Euxestini, the Anommatini, and the Metacerylonini of Heinze (1944) are, for the most part, primitive for the family, and that all three tribes might be given subfamily rank. Of the eight known genera, only one, Hypodacne, occurs in America north of Mexico. The genus Euxestus Wollaston, however, includes a widely distributed Neotropical species which might be expected to occur in southern Florida (see below) .




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19751 Lawrence &' Stephan - Cerylonidae I39 Hypodacne LeConte
Hypodacne LeConte, 1875: 170. Type species, by monotypy, H. punctata LeConte.
Euxestus, of authors (not Wollaston) .
Sen Gupta and Crowson resurrected LeConte7s name for a group of species, usually included in Euxestus, which have simple tarsi, lacking the characteristic ventral lobe on the first tarsal segment. In addition to the North American H. punctata, several Australian and New Zealand species are included.
Hypodacne punctata Leconte
(Fig. 20)
Hyfodacne $unctata LeConte, 1875 : 171. Type locality: Eastern United States. Holoype, No. 6763 M.C.Z.
This species is easily distinguished from other North American cerylonids by the highly convex and oval body, which is longer than 1.5 mm., widely separated and posteriorly closed procoxal cavities, distinct frontoclypeal suture and characteristic antennal club, and the lack of pronotal antennal cavities, femoral lines on the abdomen, and crenulations on the last visible ventrite. The related Euxestus erithacus Chevrolat occurs in the Greater Antilles and might be found in southern Florida, but that species is smaller in size and bears a distinct ventral lobe on the first tarsal segment, a feature absent in Hypodacne.
Distribution. Known from scattered localities throughout eastern North America, from southern Ontario to Florida and west to Kansas and Texas.
Biology. According to Stephan (1968)) this species occurs in the galleries of carpenter ants (Camponotus) in southern Ontario. Speci- mens were observed crawling on walls of carpenter ant galleries in oak, elm, and beech. The larva of H. punctata is unknown, but that of the Australian species, H. bivulneratus (Lea), was described by Sen Gupta and Crowson (1973 : 381) from specimens collected in leaf litter and decayed wood.
Anommatinae Ganglbauer
This subfamily includes the two Palaea,rctic genera Abromus Reitter and Anommatus Wesmael, the latter of which has been introduced into North America. Ganglbauer ( 1899) originally con- sidered this tribe to be related to cerylonids, but Crowson (1955)



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placed the group in his Merophysiidae. Sen Gupta and Crowson (1973) recognized its affinities to the Cerylonidae, and especially the Euxestinae, after the description of the Anommatus larva by Dajoz (1968).
Anommat us Wesmael
Anommatus Wesmael, 1835: 338. Type species, by monotypy, A. terricola Wesmael [= A. duodecimstriatus (Muller) 1. This genus is native to Europe, where it is represented by 49 species. It has been recently revised by Dajoz (1965). Anommatus duodecimstriatus ( Muller)
(Fig. 23)
Lyctus duodecimstnatus Muller, 1821 : 190. Type locality: Odenbach, Ger- many.
(For complete synonymy, see Dajoz, 1965.) This species may be distinguished by the elongate form, distinct frontoclypeal suture, apparently I-segmented antennal club, 3-seg- mented tarsi, and the lack of eyes or wings. It superficially resem- bles the eyeless colydiid Aglenus brunneus (Gyllenhal) , which differs by having a 3-segmented antennal club, 4-segmented tarsi, and hidden antennal insertions.
Distribution. Fairly widely distributed in Europe and extending at least to Turkey and Algeria. Recorded also from Madeira, St. Helena, South Africa, Chile, Tasmania and North America (Cooper, 1962). North American specimens collected at Rochester, New York ('Cooper, 1962 ; Peck, 1972) ; Cincinnati, Ohio (Dury, 1928) ; and Lake Forest, Lake Co., Illinois (W. Suter, Nov. 7, 1959). Biology. Adults have been collected from litter and damp soil under railroad ties, under stones, around grass roots, and from grass cuttings. The Illinois specimen was taken in a tree hole. Larvae have been found in soil at the base of a tree and in leaf mold (Dajoz, I 968 ; Sen Gupta and Crowson, I 973 ) . No males have been found in North America, and Cooper (1962) and Peck (1972) have postulated that our populations may be parthenogenetic. Murmidiinae Jacquelin DuVal
This corresponds to the Murmidiinae of Sen Gupta and Crowson, except for the exclusion of Ostomopsis (see Ostomopsinae below). The group may be characterized by the presence of a frontoclypeal



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19751 Lawrence &? Stephan - Cerylonidae 141 suture and prothoracic antennal cavities, and it includes the three genera Murmidius, Mychocerus, and Botrodus, all of which are represented in North America. Casey (1895) also included the Lapethini and the Eupsilobiini, with the single genus Eupsilobius. According to Sen Gupta and Crowson (1973)) the lapethines should be transferred to the Ceryloninae, while Eupsibbius Casey, a junior synonym of Eidoreus Sharp, should constitute a distinct subfamily of Endomychidae.
Murmidius Leach
Murmidius Leach, 1822: 41. Type species, by monotypy, M. ferrugineus Leach [= Murmidius owah (Beck)].
Ceutocerus Germar, 1824: 85. Type species, by monotypy, C. advena Germar [= Murmidius ovalis (Beck)].
This genus contains five Neotropical species and five from the Old World. One of th,e latter, M. ovalis, has been introduced in stored products to many parts of the world, including North America. Hinton (1942b) provided a key to the Old World species. Murmidius ovalis ( Beck)