190 



THE EVOLUTION THEOKY 



tant in this case, since the already existing sucking apparatus only 

 required to be a little altered. 



Again, in the order Hemiptera (Bugs) the suctorial proboscis does 

 not owe its origin to a diet of flowers, for no member of the group is 

 now adapted to that mode of obtaining food. 



The proboscis of the Lepidoptera, on the other hand, depends 

 entirely on adaptation to honey-sucking, and we may go the length 

 of saying that the order of Lepidoptera would not exist if there were 

 no flowers. This large and diverse insect-group is probably descended 

 from the ancestors of the modern caddis-flies or Phryganidse, whose 

 weakly developed jaws were chiefly used for licking up the sugary 

 juices of plants. But as flowering plants evolved the licking 



apparatus of the primitive butter- 

 flies -developed more and more 

 into a sucking organ, and was 

 ultimately transformed into the 

 long, spirally coiled suctorial pro- 

 boscis as we see it in the modem 

 butterflies (Fig. 47). It has taken 

 some pains to trace this organ 

 back to the biting mouth-parts of 

 the primitive insects, for nearly 

 everything about it has degene- 

 rated and become stunted except 

 the maxillae {mx'). Even the 

 palps (|J77i) of these have become 

 so small and inconspicuous in 

 most of the Lepidoptera that it 

 is only quite recently that re- 

 of them have been recognized in a minute protuberance 

 among the hairs. The mandibles (md) have quite degenerated, 

 and even the under lip has disappeared, and only its palps are 

 well developed (B, p^.). But the fii-st maxillae (ma;'), although 

 very strong and long, are so extraordinarily altered in shape and 

 structure that they diverge from the maxillae of all other insects. 

 They have become hollow, probe-like half -tubes, which fit together 

 exactly, and thus form a closed sucking-tube of most complex 

 construction, composed of many very small joints, after the fashion 

 of a chain-saw, which are all moved by little muscles, and are sub- 

 ject to the will through nerves, and are also furnished with tactile 

 and taste papillae. Except this remarkable sucking proboscis there 

 are no peculiarities in the body of the butterfly which might be 



F1G.47. Head of a Butterfly. ^,seenfrom 

 in front, au, eyes, la, upper lip. md, rudi- 

 ments of the mandibles, pm, rudimentary 

 maxillary palps, mx', the first maxillae 

 modified into the suctorial proboscis, pi, 

 palps of labium or second maxillse, cut off 

 at the root, remaining in B — which is a side 

 view, at, antennae. Adapted from Savigny. 



mams 



