338 MR FRANK BALFOUR-BROWNE ON 



The female genital armature is apparently part of the eighth abdominal segment, 

 so that Peytoureau's statement that, except in Dytiscus, in the Coleoptera this is always 

 on the posterior margin of the seventh segment, is apparently incorrect. 



The spinning apparatus, which is somewhat different from that described for 

 Hydrophilus, is described in some detail. The spinnerets, from the apices of which the 

 silk runs, do not appear to have any duct running through them, and it is suggested that 

 the silk flows out on their surfaces. 



The method of building the egg-cocoon seems to be quite different in Hydrobius from 

 what it is in Hydrophilus, and whereas in the latter case it is stated (Lyonnet) that the 

 eggs are laid after the body of the cocoon is completed, in Hydrobius, the egg-laying 

 commences very soon after the cocoon is begun. 



The development of the embryo is followed in the living egg. In the final stage the 

 embryo swells up so as to completely occupy the shell, and a cephalic pulsating organ, 

 which is probably a pharyngeal pump, appears. It is suggested that this absorbs the 

 periembryonal fluid and thus enables the embryo to completely occupy the shell. 



The larva shows certain peculiar habits, one of which is that it normally has its gut 

 partly filled with air-bubbles, and as it takes its first " air-drink" shortly after hatching, it 

 is suggested that the ribbon attached to the egg-cocoon, and which normally reaches 

 the surface of the water, is for a pathway by which the larvse may get to the air. In 

 the same way perhaps the mast of the Hydrophilus cocoon may be useful. 



Another peculiarity of the larva is that it can apparently only feed out of the water. 

 The prey, which consists chiefly of daphnids, is sucked' dry, the solid portions being 

 left as useless. 



BIBLIOGRAPHY. 



Heider, K., 1889, Die Embryonalentwicklung von HydropMlus piceus, L. I. vol., Jena. 



Henneguey, L. F., 1904, Les Insectes, Paris. 



Kowalevsky, A., 1871, " Embryologische Studien an Wurmen u. Arthropoden," Mem. Acad. St. Petersboury, 



(7), t. xvi. 

 Laker, A. G., 1881, "The Cocoons of Hydrophilus piceus and Hydrobius fuscipes," Entomologist, xiv., 



pp. 82-84. 

 Lyonnet, P., 1829-32, " Recherches sur l'anatomie et les metamorphoses de differentes especes dTnsectes," 



Mem. du Museum d'llist. Nat. Paris, xviii.-xx. 

 Mi all, L. C, 1895, Natural History of Aquatic Insects, Macmillan &, Co. 

 Miger, F., 1809, "Mem. sur les larves des Insectes Coleopteres aquatiques. I. Mem. sur le grand 



llydrophile," Assoc, du Museum d'llist. Nat., xiv. 

 Packard, A. 8., 1898, Text-book of Entomology, Macmillan & Co. 

 Pkytoureau, A., 1895, Morph. de VArmure genitale des Insectes, Paris. 

 ScmdDTB, J. C, 1861-3, "De metamophosi Eleutheratormn Observationes. Bidrag til Inseckternes 



Udviklings-histoiie," Naturliistorisk Tidsskrift, Kjobenhavn. 



