HEMIPTERA. 



173 



Fig. 144. — Cicada tibicen. 



it has been improperly termed) and to the Dog-day Harvest-fly 

 (Fig. 144) to give an idea of the more striking characters of this 

 family. 



The species are generally of large size, with a subconical body. 

 The head is wide and blunt, with prominent 

 eyes on the outer angles, and three bead-like 

 ocelli arranged in a triangle on the vertex. 

 "The mesothorax is the largest segment, and 

 the metathorax is reduced to a narrow scale. 

 A very conspicuous feature in all of them is a 

 cross-like prominence on the hind end of the 

 former, which adds great firmness to this im- 

 portant part of the chest. The wing-covers 

 are nearly elliptical, longer than the body, 

 parchment-like, but generally transparent, and 

 with a series of eight areoles at the tip ; but the 

 hind wings are more membranous, scarcely ex- 

 ceeding half the length of the former, and with 

 an apical series of six areoles. Their legs are short and stout, not 

 fitted for leaping, the fore-thighs quite thick, armed with two or 

 more thick teeth ; also, the hind shanks are bristly, and have a series 

 of sharp spines on each side. 



" But the most distinctive peculiarity, which has no parallel in 

 any of the other groups, appears in the organs of sound (of the 

 males). These consist of two large parchment sacs, ribbed and 

 gathered into numerous plaits, furnished with powerful muscles, and 

 situated in large cavities at the base of the abdomen. When in 

 action, the air is driven in great force against the ribbed surfaces, and 

 vibrations are set up which produce the sound in accordance with 

 the number and form of the fluted spaces and ribs." (Uhler.) 



The Dog-day Harvest-fly, or Lyerman, Cicada tibicen. — The 

 shrill cry of this species, which is the most prominent of the various 

 insect sounds heard during the latter part of the summer, has 

 brought its author into prominent notice. This insect varies both 

 in size and colors. It commonly measures 50 mm. (2 inches) to the 

 tip of the closed wings; it is black and green, and more or less 

 powdered with white beneath. The transformations of this insect 

 are similar to those of the following species, except that it requires 

 only two years for its development. It differs also in seldom, if ever, 

 occurring in sufficient numbers to be of economic importance ; but a 



