74 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



conflicting results of his own work and that of Smidt- 

 Schwedt* are compared by Dr. Boving. Th<? first half of 

 the work deals with previous work on the group, and especially 

 with that of the above-mentioned authors, with which the 

 author differs about the much-discussed points on the respira- 

 tion and the feeding of the larva and the making of the cocoon. 



The second part presents the author's own observations and 

 results and is supplemented by some very fine plates. 



The main points in the life history of these beetles will be 

 familiar to most of the members ; the eggs are laid in clusters 

 on the water plants on which the adults feed ; each species feed- 

 ing as adult on the same plants on which the larvae are found 

 under water. The larvae attach themselves to the roots, partly 

 by the weakly developed legs, but more especially by two 

 stout spines on the eighth abdominal segment ; they feed on 

 the juices of the roots and when full grown make a tough, oval 

 cocoon attached to the root. 



Doctor Boving has through many observations in the field 

 and in the insectary, as well as through anatomical studies, 

 proved that the breathing of these larvae is done solely through 

 the caudal spines, which according to him are nothing more 

 than highly specialized spiracles ; these are inserted into the air- 

 cells of the plant from which the fresh air is supplied ; the 

 other normal spiracles are used only to expel the used air, which 

 escapes as minute bubbles. He shows that the air passes 

 through the thin membranes covering the openings in the 

 spines, directly from the air-cell of the root to the tracheal 

 system, and that only in this way is the breathing possible ; 

 not as suggested by Sanderson and MacGillivray by the absorb- 

 tion of air from the water, or by the catching of air-bubbles 

 from the root when the epidermis is torn by the spines. The 

 entire inbreathing takes place through the caudal spines, the 

 entire outbreathing is done through the normal abdominal 

 spiracles. 



Relating to the feeding, Doctor Boving shows that it is es- 

 sential for the larva to exclude the water from the place where 

 it gnaws the root ; this it accomplishes by drawing the head into 

 the thoracic segments and forming a watertight compartment 

 by pressing the anterior part of the body against the root; it 

 then bites out a plug from the surface of the root and inserts 

 its head, filling out the opening completely ; it feeds only on 

 the juice of the plant, swallowing no solids. I loving suggests. 

 though he has not been able to actually prove it, that the larvae 

 do not void any excrement at all. 



* Berliner Ent. Zeitschrift, xxxi, p. 325-334, 1887. 



