MICROSCOPIC OBJECTS. 76 



Fig. 151. Tongue of Blow -Fly (Musca vomitoria), x 20. 



One of the most marvellously constructed instruments 

 with which insects are furnished is the proboscis, or tongue, 

 of the Blow-Fly, to thoroughly describe which would take 

 many pages. The broad part at the top of the drawing 

 represents the two lobes of the ligula; these lobes contain 

 a number of minute tubes, kept partially open by rings ; and 

 through these fine channels the fluid sugar is thoroughly 

 filtered before it enters the mouth. A duct, which serves to 

 convey a fluid with which to soften sugar and other sub- 

 stances, also runs into the tongue. Both of these necessary 

 parts are kept in action by the muscularity of the pharynx, 

 which part is at the bottom of the drawing. The contraction 

 of this sends the salivary fluid to the food to moisten it, and 

 the dilatation of the same forms a suctorial power, with which 

 the liquid food is conveyed into the mouth. 



The proboscis must be dilated by pressing the thorax of the 

 Fly, then cut off with a fine pair of scissors (the Fly having 

 been previously killed in alcohol), next placed gently in its 

 natural position, squeezed flat, dried under pressure, soaked 

 in turpentine until transparent, and mounted in balsam ; or 

 it may be mounted, without preparation, in glycerine. 



Fig. 152. Lancets of the Female Mosquito (Culex mosquito), 



xlO. 



Another form of tongue is found in the Gnats, of which 

 this drawing may be taken as a type. It consists of a labrum 

 or tongue, which is the largest part (see drawing) ; another 

 part, slightly smaller, called the labium, forms a kind of 

 sheath for the mandibles and maxillae, which in this case 

 are generally called the setae or lancets; they are four in 

 number ; three of them have been separated from the labium, 

 or sheath, so as to show their structure, two of them being 

 furnished with fine teeth, while the other two terminate in a 

 fine sharp point. In addition to the irritation caused by the 

 action of these setse, a drop of poison is instilled by them into 

 the wound, so as to render the blood more liquid for the 

 suctorial action of the labium. The other parts represented 

 in the drawing are the long pilose antennae, and the two short 

 and thick bodies called the maxillary palpi; the eyes are also 

 shown. 



These objects simply require to be placed in their natural 

 position, dried under strong pressure, and mounted in balsam 

 as usual. 



