OF WASHINGTON. 249 



discoloration of the bai'k which results from the entrance of the 

 very fine, almost microscopic, setae. If punctured by the beak 

 itself comparatively large holes would be at once apparent. 



If observations on this point were wanting, the structure of the 

 beak itself would at once indicate that it could not be employed 

 as a piercing organ. The beak or labium of all hemipterous 

 insects, so far as I have examined them, is clothed to and on the 

 very tip with numerous hairs projecting anteriorly, which would 

 make the piercing of any hard substance quite impossible with 

 out tearing of and rupturing the hairs ; and what is more, the 

 beak is never very sharply pointed, or smooth or chitinous at the 

 tip. Nearly every collector, also, has experienced the sting of 

 some large hemipterous insect, and has doubtless mistaken the 

 quick. thrust of the maxillary setae for an actual puncture by the 

 beak. 



Dr. Gill asked as to the true function of the beak. Mr. 

 Marlatt stated that it was simply a support for the setae. Dr. 

 Gill asked whether, with the Heteroptera, as with Rediivius and 

 Nepa, it is not the beak which pierces. Mr. Marlatt thought 

 not, and was of the opinion that in these cases, while it is 

 generally supposed that the beak actually penetrates, in reality 

 the puncture is made by the setae contained in the beak. Dr. 

 Riley said he would much like to know how the Homoptera 

 draw up their nourishment, particularly in the case of the 

 Coccidae. He agreed with Mr. Marlatt that, in the Homoptera, 

 the beak does not penetrate, but he thought that with the 

 Heteroptera it does puncture. How the setae work in the 

 Homoptera is a puzzle. Mr. Marlatt replied that the four 

 bristles are probably closely applied to form a sucking tube. 

 The suction is probably the reverse of the operation of oviposi- 

 tion with Thalessa and other long-tailed Ichneumonids. 



Mr. Howard stated that Mr. Marlatt's demonstration convinced, 

 him fully of the incorrectness of Dr. Smith's views in considering 

 the beak to be the homologue of the galea of the maxillae. Dr. 

 Smith had evidently been misled by his own conclusions from 

 the study of the dipterous mouth, and had begun the study of 

 the homopterous mouth with the preconceived idea that the 

 beak must be a galea. He said that while Mr. Marlatt's proof 

 was perfect as regards the Hemiptera, it by no means neces- 



