On Aquatic Carnivorous Coleoptera or Dytiscidee. 245 
pigment, and has besides large sharply defined patches of nearly black pigment. 
In Pelobius the basal portion of the wing is pigmented with yellow, while the 
outer portion is smoky. 
The wings of the Dytiscide in their neuration vary very little and are extremely 
similar to those of the Carabidee and Cicindelide so that no certain character can 
be pointed out as distinctive. Usually the anal area is larger in the Dytiscidee than 
it is in the Carabide, but in the Noterides this part is quite as small as in the Cara- 
bide. The oblong pigment mark near the middle of the hind margin appears to be 
wanting in the Carabide, but is also frequently absent in the water beetles 
(Bidessus, Eretes). In Amphizoa the pigment mark is very largely developed, but 
the anal area is rather small ; in Pelobius the pigment mark is absent, and the 
anal area is small as in the Carabide, 
I have already mentioned that in one species of the family (Colymbetes bifarius 
No. 757 Agabus) the wings are rudimentary : on careful examination of this species, 
the costal, subcostal, and median veins are found to exist, as does also the accessory 
vein between the subcostal and median veins, and even the flexuous adjunct to the 
latter ; and the pigment mark is largely developed ; the interior portion of the 
wing is however scarcely represented, a portion of the submedian vein is indeed 
present and forms the boundary of the wing, but the parts that should lie internal 
to this are quite undeveloped. 
Although the Dytiscide live in water, they are only adapted for aquatic life by 
modifications almost confined to their external structure. As however, owing to the 
modifications of their legs for swimming, they are very ill adapted for walking, it is 
highly important to them that they should possess wings to transport them to fresh 
localities when, as very frequently happens, the pools of water in which they have 
been living dry up. That these dwellers in the water should possess highly developed 
wings is not therefore so peculiar as it at first sight appears; but it certainly is 
2 remarkable fact that their wings should be so extremely similar to those of the 
Carabidee and Cicindelidee. The Cicindelide especially are very rapid runners, and 
take very frequent short flights, opening their wings with extreme haste, to enable 
them to pounce on their prey ; the Dytiscide on the other hand, only very rarely 
fly, their flights are then probably for long distances, and the msect only takes to 
flight at all with difficulty and after a laborious preparation of itself for the purpose ; 
it is then certainly a most remarkable fact that the wings in these two families 
should be so extremely similar. 
The development of an elegant pigmentation on the wings of certain species of 
the family (especially Hydaticus flavolineatus No. 1024) is specially worthy of the 
attention of those who may be engaged in considering the origination of colour in 
insects ; the wings in the Dytiscidee are completely withdrawn from all the external 
influences that may be supposed to regulate the development of colour and pattern, 
and yet they show extreme differences in the development of pigment, and when 
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