218 



COLEOPTERA 



CHAP. 



like structure is provided with a little mast, which is supposed by 

 some to be for the purpose of securing air for the eggs. Hclo- 

 chares and Spzrclieus (Fig. 100) carry the cocoon of eggs attached 



to their own bodies. Philydrus constructs, 

 one after the other, a number of these 

 egg-bags, each containing about fifteen 

 eggs, and fixes each bag to the leaf of 

 some aquatic plant ; the larvae as a rule 

 hatch speedily, so that the advantage of 

 the bag is somewhat problematic. 



The larvae of the aquatic division of 

 the family have been to a certain extent 

 studied by Schiodte and others ; those of 

 the Sphaeridiides the terrestrial group 

 of the family are but little known. All 

 the larvae seem to be predaceous and 

 carnivorous, even when the imago is of 

 vegetable - feeding habits ; and Dumeril 

 FIG. 100. Spercheus emar- gtates that in Hydrous carciboidcs the 



ginatus 9- Britain. A, 



Upper surface of beetle ; alimentary canal undergoes a great 

 B, under surface of abdo- c h ange afc the period of metamorphosis, 



men, with the egg - sac _ ' 



ruptured and some of the becoming very elongate in the adult, 

 ;s escaping. though in the larva "it was short. The 



legs are never so well developed as they are in the Adephaga, 

 the tarsi being merely claw-like or altogether wanting; the 

 mandibles are never suctorial. The respiratory arrangements 

 show much diversity. In most of the Hydrophilides the process 

 is carried on by a pair of terminal spiracles on the eighth 

 abdominal segment, as in Dytiscidae, and these are either 

 exposed or placed in a respiratory chamber. In Berosus the 

 terminal stigmata are obsolete, and the sides of the body bear 

 long branchial filaments. Cussac says that in Sperclieus (Fig. 

 101) there are seven pairs of abdominal spiracles, and that the 

 larva breathes by presenting these to the air ; l but Schiodte 

 states that in this form there are neither thoracic nor abdominal 

 spiracles, except a pair placed in a respiratory chamber on the 

 eighth segment of the abdomen, after the manner described by 

 Miall as existing in Hydrobius. No doubt Cussac was wrong in 

 supposing the peculiar lateral abdominal processes to be stig- 



1 Ann. Soc. cnt. France, xxi. 1852, p. 619. 



