296 THE ENTOMOLOGIST. 



16 per cent. A crossing with luctuosa ? resulted in some weakly 

 larvae, the converse being unfruitful. 



Spilosoma hybr. inversa, Car., was the name I gave originally 

 to a very rare black-and-white spotted $ var. of standfussi. Last 

 year, however, such quantities of an insect, named inversa by 

 me, the offspring of standfussi ? and rustica $ , came into the 

 market, that at present no large collection can be without it. 

 The name inversa may therefore lapse for the rare form of 

 standfussi, and stand for the offspring of standfussi ? and rustica 

 $ ; a pair of this hybrid are shown at figs. 12 and 13. 



The forms figured at 14 and 15 are from a combination of 

 mendica $ and inversa 2 . This new mixture is very similar in 

 colour to the dark form of standfussi which I named var. mus., 

 and I have been able to cross it further successfully with rustica 

 and inversa. 



A GUIDE TO THE STUDY OF BRITISH WATERBUGS 

 (AQUATIC RHYNCHOTA). 



By G. W. Kirkaldy. 



(Continued from p. 204.) 



(y) Gerris, Fabr. (restricted). 



= Limnotrechus, Stal, 1868. 



In this section, the typical one of the genus, there are seven 

 British species (one of which is, so far as our islands are con- 

 cerned, restricted to Scotland), separable by the accompanying 

 table : — 



1. Intermediate tibiae not more than 2^ times 



(rarely more than twice) as long as the tarsi;* 

 posterior lobe ("disk") of pronotum nearly 

 always more or less rufescent ... 2 



— Intermediate tibiae rarely (if ever) less than three 



times as long as the tarsi ; posterior lobe of 

 pronotum not rufescent .... 4 



2. Abdomen longitudinally channelled beneath ; 



submarginal flavescent line of pronotum con- 

 tinued on the anterior lobe .... 4. (?) asper, Fieb. 



— Abdomen longitudinally keeled beneath ; sub- 



marginal flavescent line not continued on an- 

 terior lobe of pronotum ..... 3 



3. Robust ; very wide across intermediate coxae ; 



abdomen shallowly depressed on each side of 



central keel . . . . . . .5. costce, Schaff. 



* The intermediate legs are so long that the difference between " 2^ " 

 and " 3 times" is easily recognisable. 



