Revision of the Notonectide. 399 
varying from almost stramineous to full rich green; after 
death the green fades, and these parts acquire a sordid 
stramineous or even brown hue. ‘The apical rostral 
segment appears to be constantly piceous. 
Great hopes were entertained by me that the 7 
genitalia would furnish a reliable diagnostic character, 
but in the few species (N. glauca, N. lutea, N. trrorata 
and N. undulata), of which suitable material was avail- 
able, these hopes have not been realized. 
Geographical Distribution. 
The genus Notonecta is distributed practically over the 
world, though its home seems to be in North America ; 
it is very difficult to define any special regions, as water- 
bugs admittedly have no respect for such limitations. 
N. glauca is distributed throughout Europe, N. Africa, 
Siberia, Persia, N. India, and probably Brazil; the 
allied species, N. undulata, N. americana and N. varia- 
bilis occupy practically the whole of America, while 
N. mexicana and N. insulata occur plentifully in North 
and Central America and in the northern states of South 
America; N. montandoni has been found in China and 
Burma, 
Only one species, N. lactitans, has been found as yet in 
Africa south of the Sahara, but it extends from Guinea 
to the Cape of Good Hope.* 
Throughout this paper the localities derived from 
specimens seen by myself are alone given, unless other- 
wise stated. 
SpecirerumM TABULA. 
1 (2) Pronoti basis latitudo pronoti longitudine duplo atque 
dimidio major; metanotum scutello fere duplo longius. 
(America bor, et merid.) 1 mexicanu, Am, Serv. 
2 (1) Pronoti basis latitudo pronoti longitudine duplo atque 
dimidio minor (plerumque fere duplo major) ; meta- 
notum scutello paullo longius. 
3 (4) Vertex synthlipsi amplius quinquies latior, 
(America bor.) 11 whler/, Kirk. 
* T shall be greatly indebted to any South American or South 
African entomologist who will send me the Notonectw of his 
country. 
