180 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



sensitive to rapid changes in temperature and with but few ex- 

 ceptions cannot stand desiccation in the slightest degree. The 

 body structure and activities of H. uhlerii are admirably adapted 

 to overcome these adverse circumstances of environment, not 

 by resisting the elements but by making it possible for these 

 animals to change their position in the soil with the variations 

 of climatic conditions so as to always be in a stratum where 

 the environment is compatable with their development or at least 

 their existence. ' As the sand dries out, or as the cold weather 

 approaches they rapidly burrow downward, conversely as mois- 

 ture rapidly saturates their porous nidus or the temperature rises 

 they move as rapidly upwards, and may even make daily upward 

 and downward migrations to accommodate themselves to the 

 ephemeral changes in temperature and humidity. The nature 

 of their habitat makes the construction of permanent burrows 

 impossible, hence the remarkable development of their bodies. 

 The extremely broad palmate and digitate retractile anal lobes, 

 form a backwardly directed pushing organ wonderfully de- 

 signed to prevent any backward movement of the abdomen w hen 

 burrowing in the loose sand, the spined caudal appendage on the 

 ninth abdominal segment also assisting in this function. When 

 moving foreward the larva contracts the abdomen by completely 

 invaginating the anterior area of each abdominal segment within 

 the posterior area of the preceding segment; the anal lobes are 

 retracted as are also the lateral and ventral ambulatory papillae, 

 thus offering no resistance; the anterior part of the body is pre- 

 vented from moving backward by the broad, spine beset surface 

 of the tibise and tarsi of the legs, which may be assisted by the 

 mandibles. The lateral papillae and anal lobes are now excerted 

 and the body starts to exert a pressure foreward by the longi- 

 tudinal expansion of the segments, the mandibles work rapidly 

 in an absolutely lateral plane, their concave outer surface press- 

 ing back the sand on each side much as do the short marinae of 

 the mole, the mouthparts with their stout brushes probably also 

 assist in clearing the way. These brushes undoubtedly prevent 

 sand from being forced into the buccal cavity. When on a hard 

 surf;! re the larva moves the head and mandibles very rapidly, 

 at the same time tremulously jerking the fore part of the body 

 from side to side. The legs are also kept rapidly moving. When 

 placed on moist blotting paper the head is applied to the paper, 

 and the stout mandibles soon tear an opening through the fibers 

 of the paper, the tearing action is confined to the outward thrust 

 of the mandibles, the stout teeth on the inner surface not com- 

 ing into play and probably only being used to lacerate plant tis- 

 rhen feeding. When moving backward the ventral papilla 1 

 play the most important part. These are directed forward and 



