«b EXTERNAL ANATOMY OF INSECTS. 



approach to Diptera ; and on this account the examination of 

 their mouth is not unimportant. The insertion is a small 

 triangular piece, on which the disk and feeler-bearer are 

 seated. Their union is usually by a distinct longitudinal 

 suture. The feeler is slender, five or six-jointed, and situated 

 close to the base of the blade. The blade is long, slender, 

 flexible, and elastic ; it unites with the ligula, and labial- 

 feelers in forming a honey -sucking tube. In all these re- 

 spects, excepting the union with the ligula, the feeler-jaws 

 of the bees very closely resemble those of Lepidoptera. In 

 Nomada the feeler and the blade are of equal length. In 

 Saropoda the feeler is about one-fifth as long as the blade. 

 In Bombus it is scarcely one-fifteenth the length. In Mclecta 

 the disk and blade are of nearly equal length : the feeler is 

 about one-third their length. In Andrena, Halictus, Dasy- 

 poda, Colletes, Hylceus, and Sphecodes,^ the length of the 

 blade is much diminished. The division of the other parts is 

 in these genera much more manifest. Vespa, Odyneriis, &c. 

 display a greater change : in these the feeler is much longer 

 than the blade. In Hedycrum the feeler-bearer is longer 

 than the insertion and stalk together : the galea, or helmet, 

 also reappears in a large oval form ; the blade is short ; the 

 feeler is long.*^ Passing through the Fossores, the Pupivora, 

 and the Tenthrediniles, we arrive very nearly at the mouth of 

 Coleoptera. In all these the helmet of the feeler-jaw is present 

 under some of its various modifications : it is the terminal 

 portion, and its variations are of the greatest importance as 

 distinguishing characters. 



In Coleoptera, the feeler-jaws have assumed much more the 

 appearance of the mandibles, than in any class through which 

 we have traced them. Still it is far from certain whether they 

 are, even in this class, employed for mastication. Kirby has ex- 

 cellently suggested that, under their present form, they are the 

 holders or retainers of the food, while the mandibles are em- 

 ployed in masticating it. Their form and situation certainly 

 favour this idea. Dumeril supposes they also assist in masti- 

 cation, f The insertion of the feeler-jaw in this class is but 



^ With the exception of S. monilicornis, before noticed. 



^ The description is from the dissections of Hedychrum in Curtis's British 

 Entomology. 



' C'est avec les mandibules que Tinsectc coupe, arrachc ou retient les ahmens ; 



