Vol. LI. LONDON, M:BRITARY, 1910. No. 2 



POPULAR AND PRACTICAL ENTOMOLOGY. 

 Notes on the Habits of Heterocerus Beetles. 



by g. b. claycomb, university of illinois, urbaxa, ill. 



In the hot, dry days of summer, when the creeks run low and the mud bars 

 become numerous along the margins of the streams, a common sight on this 

 recently deposited mud is the network of lines which mark and ramify the 

 surface. Investigation shows clearly that some small animal has pushed its 

 way through the soft alluvium and formed little tunnels in the freshly exposed 

 sediment left by the receding water. These little subterranean passages were a 

 source of great perplexity to the writer until the summer of 1916, when the 

 entire mystery was revealed as if by magic. 



Along a small creek in western Illinois on a day late in July, the entire life- 

 history of the little builder of the burrow was found in all completeness. Near 

 the water (pi. I, fig. 1), just beneath the surface of the soft squashy mud, were 

 the tunnels, freshly made. Farther back on the dryer portion of the bar, the 

 tunnels were more numerous and the elevation of the soil which marked the 

 passages was more distinct, due to the drying of the earth. Still farther back 

 the lines formed, in places, an almost unbroken mat, so extensive had the net- 

 work become (pi. I, fig. 2). On the higher, firmer portions of the deposit, 

 among the older less distinct galleries, were little cases with chimney-like ex- 

 tensions projecting from the mud (fig. 3). 



Here then was the life-history of these interesting beetles in all its com- 

 pleteness within this very limited area. The adult beetle (fig. 4) was found to 

 be the maker of the tunnels in the fresh mud near the water. Several were 

 captured within the burrows, and others, when disturbed, forced their way out 

 through the mud and flew aAvay. In these newly constructed passages are laid 

 the eggs in small masses (fig. 5). The eggs hatch into active running larvai 

 (fig. 6) which greatly extend the home already started for them by the adult, 

 growing to a length of 7 or 8 millimetres, the larv?e construct for themselves 

 the mud chambers with the peculiar little chimneys extending upward from them 

 (fig. 3) The openings of these chimneys are usually closed near the top by a 

 very thin layer of dry mud. These structures become firm and strong after 

 they are dry. In the chamber the larva changes to a pupa (fig. 8). Beside the 

 larvce and pupa?, several adults were found within the cells (fig. 3). 



The beetles were identified for me by Mr. A. B. Walcott, of The Field 

 Museum of Natural History, Chicago, who says: "The sending represents two 

 species, the larger and paler ones are Heterocerus pallidus Say; while the smaller 

 and darker ones are Heterocerus tristis Mann." The adults of these tAvo distinct 

 species were found together in the same limited area and in the same kind of 

 pupal cases. Their habits apparently are identical. 



The smaller beetles measured on an average 4.3 mm. in length, the larger 

 ones were slightly longer. At the time of pupation the larvae measured from 7 

 to 8 mm. in length (fig. 7). The cases averaged 10 mm. in their longest dimension. 



When the place w^as visited again a few days later, a rise of the stream had 

 obliterated the entire colony, and nothing remained but a plain mud bar. 



