72 NOTES ON THE "SCOTS GRAY " MOSQUITO 



pJiari/nx, is described as tubular, but I do not think it is so. 

 Like the rest of the lancets it is a longitudinal section of a tube, 

 and with the others clasps the central one closely so that the 

 whole appears like one organ, and as such is inserted into the 

 skin ; but when separated in dissection its elastic sides roll 

 together into a tubular form, and if immersed, by capillary 

 attraction th^e liquid will find its way into the interior, but if it 

 is traced down to its root its flat or slightly curved character 

 will be apparent. The other two pairs of lancets, the two 

 maxilhe and the two mandibles, differ also in structure. The 

 former are strong stylets armed at the point with a dozen saw- 

 like teeth, and having a strong central rib like a feather. The 

 sides of these lancets h ive also a wavy appearance, the lines 

 running at right angles to the rib. The mandibles are much 

 finer, almost transparent, and so delicate that it is difficult to 

 move them on the slide without damage. One is perfectly plain 

 but the other is pierced by a fine tubule, to which reference will 

 be made when dealing with the poison glands. In fig. 12, the 

 lancets partially separated at the base of the lahruta epiphari/nx 

 are seen. The flat ribbon-like form of the separated organs is 

 apparent. 



The Vacuum Pump. 



It is interesting to trace the ingenious method by which 

 blood or plant juice is drawn into the stomach. When the 

 lancets have been inserted a vacuum pump, placed in the middle 

 of the head, is brought into play. A view of it, with its connec- 

 tion with the lancets is seen in fig. 13. The organ or fesophagial 

 bulb, as it is called, lies just below the lobes of the brain. Fig. 

 14 is a longitudinal section of the head, showing the actuas 

 disposition of the parts. This pump is separable into three 

 longitudinal sections, as in fig. 15. These sections have hard 

 chitinous walls, but thin down at the edges where they curl away 

 from each other, and are there united by elastic tissue. Broad 

 ligamentous bands unite the plates to the upper and lower parts 

 of the head. By their contraction the bulb of the pump is 

 dilated, and the blood rushes up to fill the vacuum. On relaxa- 

 tion the walls close and force the fluid into the gullet, which is 

 surrounded by ringed muscles, and so it is passed into the stom- 

 ach. This pumping work is evidently an enjoyable one to the 

 insect. While it proceeds the hind legs are elevated and move 

 in the air with at first a quivering motion, as if thrilled with 



