THYSANOPTERA AND HEMIPTERA 189 



a decided preference on the one hand for flowers with immediately visible nectar 

 (E, EC), and on the other hand for social flowers (S), which are remarkably con- 

 spicuous and rich in booty. It is also apparent that among beetles, as generally 

 among all insects at a low stage of adaptation (wasps, lower Diptera), the frequency 

 of visits Aymim&hts part passu with the better concealment of nectar. 



With regard to colour-preference among beetles, it is to be noted that they 

 always like white and yellow flowers best. The opinion expressed by Hermann 

 Mailer (' Befruchtung,' p. 103) that beetles do not like dull yellow colours, but only seek 

 out flowers of a brilliant yellow, was withdrawn by him later (' Weit. Beob.,' I, p. 305), 

 because he found beetles visiting dull yellow flowers, an observation which was also 

 confirmed by Loew (' Beitrage,' p. 28). 



E. Other Insects that visit Flowers. 



The Thripidae of the order Thysanoptera (or of the division of Orthoptera 

 known as Physopoda) are easily distinguished from all other insects by their feet, 

 which in all the species are devoid of claws and end in a large vesicle. The species 

 of the genus Thrips barely attain at most a length of i mm., and their breadth is very 

 much less than this, so that they can easily make their way into flowers. ' Probably,' 

 says Hermann MtiUer (' Fertilisation,' p. 44), ' few of our indigenous flowers, if any, are 

 altogether exempt from their occasional or frequent visits, and though these minute 

 and extremely active little creatures certainly only convey pollen to stigmas by chance, 

 yet on account of their great abundance their value for pollination must not be 

 underrated. It must be almost impossible to keep out these guests when we try to 

 exclude pollinating insects by placing nets over plants. They seek out both pollen 

 and nectar, obtaining the former by seizing the individual pollen-grains and con- 

 veying them to the mouth by a pincer-like grasping movement of the horny 

 mandibles. They obtain nectar by apposing the mandibles and maxillae, so as to 

 form a short, conical suctorial apparatus. According to Westwood (" Introduction 

 to the Modern Classification of Insects," II, p. 4) they avail themselves also of 

 other plant juices. In all these respects their habits agree with those of the 

 Diptera.' 



MtiUer (' Fertilisation,' p. 45) supplements his account of the Thysanoptera by 

 speaking of ' the young larvae of Meloe [an oil beetle], called by Kirby (" Monogr. 

 Ap. Angl.," No. II, PI. xiv. Fig. 10), Pediculus Melitiae, and by Dufour Triungu- 

 linus, which resemble the Thysanoptera in the activity of their movements, and in 

 their minute size and slendemess, which permit entry into all flowers. Although 

 these triungulin larvae visit flowers only to attach themselves as parasites to bees, 

 they feed for the time on pollen and nectar, and not infrequently become dusted 

 with the former, so that they play a part similar to, but even less important than, 

 that of the Thysanoptera.' 



Among the Hemiptera a few bugs (Hemiptera heteroptera Latr>, regularly 

 visit flowers. The species of the genus Anthocoris (so named from their fondness 

 for flowers) are fitted, according to Miiller (' Fertilisation,' p. 31), by their small size to 

 creep into and suck nectar from flowers of very various kind. Several Capsidae and 

 Anthocoridae are found on flowers of Compositae, Umbelliferae, Cruciferae, Salix, and 



