OF WASHINGTON, VOLUME XVI, 1014 61 



by which the intersegmental skin is bent inwards and the front 

 margin of each segment is pushed into the posterior margin of the 

 preceding segment. Second, the dorso-ventral flattening of the 

 abdomen by which the lateral zone is compressed and the edges 

 of the two cuneae are made to pass further by each other. 



The telescoping movement is mainly produced by contraction 

 of the longitudinal muscle bands and the dorso-ventral movement 

 is performed by contraction of the perpendicular muscles. The 

 oblique muscles assist in both of these movements. It is a matter 

 of course that in these elementary movements of the abdomen 

 the muscles on both sides of the body act in unison. A one-sided 

 action of the longitudinal muscles controlling the telescoping of 

 the segments naturally produces a movement of the abdomen to 

 that side, movements which, however, are more or less assisted by 

 the system of transverse and especially of the oblique muscles. 

 In a great many beetle larvae, more especially in those which live 

 in galleries in wood or bark, such as Cerambycids or Trogosita, 

 or those which crawl among moist, dead leaves, such as the Hy- 

 drophilids: Enochrus and Hydrobius, are developed the so-called 

 ambulatory ampullse, which assist in the locomotion. 



There seem to be no special muscles for the retraction of these 

 ampullse; they are controlled by a mechanical combination of 

 muscles, present in all campodeiform larvae. 



It should be noted here, that the muscles only cause the con- 

 traction of these ampullae as well as the compression and telescop- 

 ing of the segments. The opposite action in these larvae by which 

 the parts are extended is not produced by the muscle system at 

 all, but by blood pressure, aided by the elasticity of the integu- 

 ment, which in some parts is especially developed for this purpose, 

 as in the sutures and circular thickening of the lateral zone. 



In discussing the foregoing paper Dr. A. D. Hopkins said: 

 am naturally gratified that the results of Doctor Boving's study 

 of the muscles of the abdominal segment in certain 'campodei- 

 form' types of coleopterous larvae has tended to verify my con- 

 clusions and suggestions relating to the external elements of the 

 'cruciform' type as represented by the scolytid larvae. 



"I want to congratulate him on this splendid piece of work 

 and the further contribution of facts bearing on this important 

 subject. It is of the greatest importance that we should be able 

 to identify the immature stages of forest insects because it is the 



