2l8 



COLEOPTERA 



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

 some to l)e for the purpose of securing air for the eggs. Helo- 

 chairs and Sperelieus (Fig. 100) carry the cocoon of eggs attached 

 to their own 1 lodies. PhUydrus constructs, 

 one after the other, a number of these 

 eo-g-bags, eacli containing about fifteen 

 eggs, and fixes eacli bag to the leaf of 

 some aquatic plant ; the larvae as a rule 

 hatch si)eedih', so that the advantao;e of 

 the bag is somewhat problematic. 



Tlie 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 

 states that in Hydrous carahoides the 

 alimentary canal undergoes a y-reat 

 change at the period of metamorphosis. 



Fig. 100. — ,'>jierrhciis cmar- 

 giiuUus ?. Britain. A, 

 Upper surtiu-e of beetle ; 

 B, under surface of abdo- 

 men, with the egg - sac 



ruptured aud some of the becoming veiy elongate in the adult, 

 eggs escaping. though in the larva it was short. The 



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

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

 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 

 exY)osed or placed in a respiratory chanilier. In Brrusus the 

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

 long branchial filaments. Cussac says that in S-pcrcheus (J'ig. 

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

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

 states that in this form there are neither tlioracic nor al)domiiial 

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

 eighth segment of the abdomen, after the manner described by 

 Miidl as existing in Hydrohius. Xo doul)t Cussac was wrong in 

 supposing the pecidiar lateral abdominal processes to be stig- 

 ^ Ann. Soc. cat. France, xxi. 1852, p. 619. 



