SCIRTES TIBIALIS, GUER., (Coleoptera-Dascyllidae), 

 With Observations on its Life History.* 



Walter C. Kraatz. 



Scirtes tibialis, Guer., belongs to the Dascyllidce, a com- 

 paratively little known family of small, inconspicuous beetles 

 which have not been extensively studied. The adults are tech- 

 nically described, but few of the life histories have been worked 

 out, despite some very interesting larval forms represented in 

 the family. Of these beetles, some (grouped together as the 

 Cyphonides, (13), from the name of the genus Cyphon) have 

 aquatic larvae, and these are remarkable in possessing long, 

 many-jointed antennae. Scirtes is of this type. 



A search into the literature revealed nothing on Scirtes 

 tibialis, except the description of the adult (4), (5), (1), and 

 only a few scattered notes on the genus, with but one paper 

 dealing with the larva (9), and that the species Scirtes cham- 

 pioni. Both Helodes and Cyphon have been the subject of a 

 number of studies, mainly in Europe, and most of the aid 

 relative to the larvae of Scirtes was obtained from the papers 

 (2, 3, 9, 10, 11, 12) on these related genera. 



OCCURRENCE AND DISTRIBUTION. 



Although aquatic, the larva is not an open-water swimmer. 

 It has a distribution restricted to that of the duckweed, Lemna 

 minor, its one food plant, which grows commonly in solid areas 

 often of some considerable extent, throughout the summer, in 

 quiet shallow waters of bays along the shores of small lakes, 

 and in suitable permanent ponds, large or small. The material 

 used in this study was obtained principally from a pond north- 

 west of Madison, Wisconsin, and also from such bays along the 

 shores of Lake Mendota and Monona. The larvae are usually 

 found resting or feeding on the lower surfaces of Lemna leaves. 



When crossing small spaces of open water, the larva moves 

 (never more than a few inches at a time) usually with ventral 

 side uppermost, just beneath the surface film. It may also be 

 dorsal side uppermost, especially when swimming down away 

 from the surface. Its motion is a characteristic wriggling one, 



* CoBtribution from the Zoological Laboratory of the University of Wisconsin. 



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