Malthodes parvulus - dorsal habitus.
Introduction
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Malthodes parvulus - dorsal habitus. |
The Malthiniae are a subfamily of Soldier Beetles (Cantharidae) which, while abundant is certain habitats, are rather poorly studied and understood. Seven species and subspecies are known from Atlantic Canada, all in the genus Malthodes Kissenwetter. There are three other genera in North America, Malthinus, Caccodes, and Frostia which have not been recorded in Atlantic Canada although Malthinus occipitalis LeConte is known from Ontario and Quebec (McNamara 1991) and could potentially occur in this region.
Bionomics
Adults cantharids whose feeding habits are known are either predators on other insects or else feed on pollen and nectar. Nothing conclusive, however, is known about the feeding habits of the Malthininae (Ramsdale 2002). Fender (1951) does mention that certain species tend to be associated either with deciduous trees, coniferous trees, or grasses and are indicative of these habitats. The species found in Atlantic Canada are always found on herbaceous vegetation.
Taxonomy
Fender (1951) is the authoritative revision of the group. The species are principally separated on the basis of various modifications of the exposed terminal abdominal tergites and sternites. Fender (1951) wrote:
"The greatest range of modification is in the genus Malthodes; the terminalia varying from a comparatively simple arrangement with the last dorsal segments simple and the seventh ventral elongate, with or without an apical notch; to a complex and intricate pattern that in some species approaches the grotesque. No other North American group of beetles, known to the author, offers such a wealth of interesting features as do these tiny creatures."
Malthodes female: apex of abdomen.
"The females of the Malthini are difficult if not impossible to place unless accompanied by the male. This is particularly true of the genus Malthodes. These females have the last ventral abdominal segment narrowly deeply emarginate. The ultimate dorsal is a small narrow median process that is subtriangular in outline with the free angle rounded. There are few females that do not conform to this pattern."
1a) Mandibles dentate on inner margin; head convex in front or becoming very narrowly concave at the extreme anterior margin of the clypeus; elytra striate punctate or confusedly rugose punctured ..... Malthinus (M. occipitalis (LeConte).
Length - 2.5-3.5 mm (Figure 8) [not recorded from Atlantic Canada.]
1b) Mandibles not dentate on inner margin; clypeus transversely concave beyond the middle; elytra confusedly rugose punctured ..... 2 (Malthodes)
2a) Last tergite normal, or produced in a normal manner ..... 3
2b) Last tergite modified, either apically or laterally ..... 5
3a) Sixth sternite strongly inflated, early encompassing last tergite ..... Malthodes similis Fender
Length - 2.5-3.0 mm (Figures 121 & 122) [Recorded: NS]3b) Sixth sternite normal ..... 4
4a) Seventh sternite apically subacute ..... Malthodes parvulus (LeConte)
Length - 1.0-1.5 mm (Figures 89 & 90) [Recorded: NB, NF, NS, PE]4b) Seventh sternite apically forked, notched, or truncate ..... Malthodes fragilis (LeConte)
Length - 2.0-3.0 mm (Figures 73 & 74) [Recorded: NB, NS, PE]
5a) Seventh sternite arcuate in profile, at most the tips spherical and slightly bent down ..... Malthodes fuliginosus LeConte
Length - 3.5-4.0 mm (Figures 143 & 144)A) Pronotum piceous to piceotestaceous with anterior and posterior margins narrowly pale ..... Malthodes fuliginosus fuliginosus LeConte [Recorded: NB, NS]
B) Pronotum entierly flavous ..... Malthodes fuliginosus flavicollis Fender [Recorded: NS]
Seventh sternite sinuate or sigmoidal in profile ..... Malthodes niger (LeConte)
Length - 3.0-3.5 mm (Figures 147 & 148) [Recorded: NB, NF]* Note Malthodes terraenovae Fender (recorded only in Newfoundland) is not yet included in this key.
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M. similis Fender. 2.5-3.0 mm. Piceotestaceous, head slightly darker, obscurely paler in front; antennomeres 1-2 testaceous; pronotum flavous to castaneous, infuscate along margin, more widely so on anterior margin; male terminalia fulvous, last segment fuscate. |
M. parvulus LeConte. 1.0-1.5 mm. Canescent, head piceous; antennae beyond antennomere 3 becoming piceous; apical abdominal segments piceous. |
M. fragilis LeConte. 2.0-3.0 mm. Piceous, head slightly darker; antennomeres 1-2, mandibles, & apex of clypeus pale; abdominal sternum of male with apical notch infuscate; female's nigropiceous. |
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No photo available |
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M. fuliginosus LeConte. 3.5-4.0 mm. Piceous, head black with apex of clypeus and mandibles flavous; antennae with segments 1-2 testaceous; pronotum with anterior & posterior margins narrowly testaceous, in some with apicies fuscous. M. f. flavicollis Fender. Pronotum yellow. |
M. niger LeConte. 3.0-3.5 mm Pale piceous to black; mandibles, antennomeres 1-2, tochanters, apices of coxae pale; apical 2 abdominal terga and basal 1/2 of apical abdominal sternum of male pale. |
M. terraenovae Fender - no information available. |
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Malthodes similis Fender |
Malthodes parvulus LeConte |
Malthodes fragilis LeConte |
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No photo available |
No photo available |
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Malthodes fuliginosus LeConte |
Malthodes niger LeConte |
Malthodes terraenovae Fender |
References
Downie, N. M. & Arnett, R. H., Jr. 1996. The Beetles of Northeastern North America. Sandhill Crane Press. Gainsville, Florida. 1721 pp.
Fender, K.M. 1951. The Malthini of North America (Coleoptera: Cantharidae). American Midland Naturalist, 46(3): 513-629.
McNamara, J. 1991. Cantharidae: Soldier Beetles. In Bousquet, Y. (Ed.), Checklist of Beetles of Canada and Alaska. Agriculture Canada Publication 1861/E, pp. 192-195.
Ramsdale, A. S. 2002. Cantharidae Imhoff 1856. In Arnett, R. H. Jr., M. C. Thomas, P. E. Skelley, & J. H. Frank (Eds.), American Beetles, Volume 2: Polyphaga: Scarabaeoidea through Curculionoidea. CRC Press, Boca Raton, USA. pp. 202-218.
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