570 Insects and Flowers 



very different from the broad-ended labellum of a house-fly. But it is in 

 the Lepidoptera that this specialization of the mouth structure in connection 

 with the nectar-feeding habit reaches its widest application and the extreme 

 of its specialization. Almost no other food than nectar is taken by the whole 

 great host of moths and butterflies (Lepidoptera), and throughout the order 

 the mouth-parts are greatly modified, so as to form a perfect flexible, often 

 very long, slender sucking proboscis (Fig. 510). (Some moths and butter- 

 flies, however, take no food at all in the imago (winged) stage and these 

 mostly have only rudimentary mouth-parts.) This proboscis is composed 

 of the two greatly elongated maxillae with their grooved inner faces so opposed 

 and locked together as to form a closed perfect tube open at its two ends, the 

 tip of the proboscis and its base, the mouth (see p. 361). By means of an ex- 

 pansion of the pharynx, to whose upper wall muscles running to the dorsal 

 wall of the head are attached, an effective pumping arrangement is obtained, so 

 that when the proboscis is thrust down a flower-cup into the nectary a stream 

 of nectar may be drawn up into the throat. The proboscis of some moths 

 is very long so as to enable them to drink from the deepest tubular corollas; 

 for example that in our larger sphinx-moths, like the common tomato-worm 

 moth (five-spotted sphinx), is 6 inches long (Fig. 509) ; in Brazil there lives a 

 sphinx-moth, Macroxilia cluentius, with proboscis 8 inches long. An orchid 

 grows in Madagascar with nectary 12 inches long, with almost an inch of 

 nectar in the bottom, but the sphinx-moth, which almost certainly exists, 

 with a proboscis long enough to reach this sweet store has not yet been found. 



The following few examples, showing varying degrees of specialization, 

 illustrate specifically many of the already generally described adaptations 

 due to the reciprocal relation between flowers and insects. 



The simpler entomophilous flowers, such as those of the apple, cherry, wild 

 rose, ranunculus, etc., brightly colored and fragrant, are mostly wide open and 

 accessible to a large variety of insect visitors. They are all abundant pollen 

 providers and some secrete nectar which is easily got at. But to get either 

 nectar or pollen the insects have to scramble over and among th: many 

 crowded stamens of the center, dusting themselves well during the process 

 with pollen, which is carried on to the next flower visited and there probably 

 rubbed off on to the stigma. In such simple forms the stigma of the first 

 flower visited is likely to be fertilized with its own pollen by the scrambling 

 visitors, if both anthers and stigma are coincidently mature (which in many 

 of these flowers is not the case). But even then if the stigma is also pollinated 

 by foreign pollen grains, it seems to be more strongly affected by them than 

 by its own pollen. Experiments have demonstrated the superior potency 

 of the foreign pollen in actually effecting fertilization. 



Open flowers of more specialization in general botanical relations, 

 although of little more as concerns the particular one under discussion, are 





