80 THE ENTOMOLOGIST. 



2. C. AFFiNis, Leach {=: atomaria in Saunders). Generally 

 distributed. Variable in size and pattern. 



Fam. NoTONECTiD^. 



The Notonectidse have also sprung apparently from a Nau- 

 coroid stem, and are usually placed in classifications between 

 the Naucoridfe and the Corixidae, an absurd position. They are 

 perhaps of all insects the most perfectly adapted for an aquatic 

 existence, their structures being very interesting 



They have been recently investigated systematically by my- 

 self.* They are characterized b}'' the rostrum being composed 

 of from three to four segments, the antennae of four, the in- 

 sertion of the anterior legs on the ijosterlor margin of the 

 prosternum, &c. 



There are two British species, each belonging to a sub- 

 family : — 



1. Posterior tibife and tarsi ciliate ; sternites keeled 

 and ciliate ; rostrum with four evident segments. 

 Eyes large. Size over 13 mill. . . . Notonecta. 



la. Posterior tibiae and tarsi not ciliate ; sternites 

 neither keeled nor ciliate ; rostrum with three 

 evident segments. Eyes small. Size under 

 3 mill Plea. 



Notonecta, t Linn6. 



The species of this genus are properly called " water-boat- 

 men," though of late years American authors have termed them 

 "back-swimmers," transferring their true title to the Corixidae. 

 In France they are named " Punaises a avirons," and in 

 Germany " Ptuderwanzen," both referring to their oar-like 

 posterior legs. 



The head is rounded and very declivous ; the eyes very large, 

 the boatman thus being able to look out, both above and below, 

 for " inside-fares." It is carnassial, feeding on any living thing 

 that it is strong enough to surprise or overpower, particularly 

 other waterbugs, larvae of Ephemerids, &c. The rostrum is stout 

 and the setae sharp, inflicting a burning smart when the bug is 

 heedlessly seized ; so severe, indeed, that it is supposed that 

 some poisonous matter must be injected simultaneously from the 

 salivary glands. 



The method of respiration is very remarkable. The boatman 

 is very buoyant, owing to the quantity of air taken in reserve 

 and its position along the sternites (which of course are upper- 

 most), so buoyant indeed that the insect is compelled to use 

 considerable exertion to remain submerged. They are fond, 

 especially during hot weather in the daytime, of remaining 



- Trans. Ent. Soc. Lond. 1897, pp. 393-426 ; and Wien. Ent. Zeit. 1904, 

 pp. 93-135. 



f From Greek noton, a bade; nehho, I swim. 



