280 COLEOPTERA 



CHAP. 



inside the stems of Dioscorea batatas, in swellings ; the group 

 Sagrides, to which it belongs, is a very anomalous one. 



i. EUPODA. The beetles of the genus Donacia are of special 

 interest. They form, with the genus Haemonia, a peculiar group, 

 w r ell represented in Europe, and also in our own country. They are 

 all connected with aquatic plants, the species of Haemonia living 

 entirely under water, while the Donacia, live in the imago-state 

 an aerial life ; though many of them enter the water with great 

 readiness, and, it is said, are able to take wing from the surface. 

 The larvae live 011 the roots of aquatic plants, and derive not only 

 nutriment but air therefrom ; they pass several months as pupae 

 (or as resting larvae waiting for pupation), under water in cocoons 

 which they construct, and which, incredible as it may seem, are 

 filled with air, not water. Exact details as to the construction 

 of these cocoons are wanting. It was formerly absurdly supposed 

 that the larva swelled itself out to the size of the cocoon it was 

 about to make, and so served as a mould, subsequently con- 

 tracting. The observations of Schmidt-Schwedt l make it, however, 

 more probable that the plant itself furnishes the air which, under 

 pressure of the water (so he supposes), fills the cocoon ; the larva 

 wounds the root, piercing to an air-vessel and then constructs 

 the cocoon on this spot, leaving to the last moment an orifice, 

 according to Schmidt, as an exit for the water. The larva uses 

 a similar artifice for obtaining air; it has no gills, but is pro- 

 vided near the extremity of the body with two sharp chitinous 

 processes which it drives into the root of the plant till it 

 penetrates an air-vessel. Schmidt thinks the processes serve as 

 conduits to conduct the air to the tracheae, but Dewitz thinks 

 the air enters the larva in a more normal manner, by means of a 

 stigma placed at the base of the piercing process. A similar 

 larva exists in Haemonia ; which genus is additionally interesting 

 from the fact that the imago lives entirely submerged. It is 

 not known how it breathes. This genus is the only member of 

 the Chrysomelidae that does not possess the structure of the 

 feet that is characteristic of the Phytophaga. The late Professor 

 Babington about sixty years ago found H. curtisi at Cley on 

 the Norfolk coast on submerged Potamoycton pectinatus, but it has 

 not been met with there for a great many years. 



The larvae of Criocerides are of two kinds, in one of which the 



1 JJ.Tliti. ent. Zdt. 1887, i>. o25, and 1889, p. 299. 



