Notes on Two Rare Darkling Beetles from Florida (Coleoptera: Tenebrionidae)

Abstract

Several years ago Triplehorn discovered a specimen of this species among a miscellaneous lot of Tenebrionidae submitted for determination by the Florida Department of Agriculture. The specimen was taken in a bird bath at Key West, Florida, 14 December 1960, by C. A. Bennett. The species was first named by LeConte in his diagnosis of the genus Branchus (1862, p. 223) and was later redescribed by the same author (1866, p. 111). Despite the fact that the 1862 description was adequate for validating the name, LeConte himself and all subsequent authors have cited the 1866 date in referring to this species. Branchus floridanus is the type of the genus by monotypy. LeConte (1866) states that the specimen (Type No. 4552, MCZ), a unique, from which his description was prepared, is from Florida, without more precise data. Dr. Howard E. Evans (in litt.) reported that there is one additional specimen of this species in the LeConte collection (Museum of Comparative Zoology, Harvard University) labelled the same as the type. The Blatchley collection (Purdue University) contains one specimen labelled Key West, Fla., 3 March 1919, W. S. Blatchley. The United States National Museum has 33 specimens collected at Miami Beach, Fla., in 1922 and 1923 (T. J. Spilman, in letter). This is the northernmost record and the largest series known to us. We have been unable to locate additional specimens although we have by no means conducted an exhaustive search. Branchus floridanus has remained an exceedingly rare beetle in collections since its discovery. Recently Weems and Robert E. Woodruff succeeded in collecting 28 more specimens. All were in sand and debris near the beach on Big Pine Key, 6 May 1961. Triplehorn picked up two additional specimens (both dead) near Tavernier on Key Largo, 17 July 1963. They were several hundred yards from the ocean beach in the grass around buildings. Little variation is evident in the specimens available, perhaps the greatest being the normal sexual dimorphism. Males are slightly smaller and less robust than the females. Males ranged from 11.9-13.7 mm in length and 6.2-7.3 mm in width. Females varied from 12.6-14.7 mm in length and 7.3-8.1 mm in width. The sculpture, punctation and dorsal vestiture of small yellowish scale-like setae are remarkably similar throughout the series. The narrow, longitudinal impunctate median line on the pronotum mentioned by LeConte is more or less conspicuous on all of them. Several other small, rounded impunctate areas in the lateral discal regions are evident and rather constant in location. These are visible without magnification.