EXPLANATION OF PLATES. Vll 



indicating the direction in which I moves on the ahdomen when the beetle creaks. 

 (Magnified.) 



Fig. 2. Acalles misellus, a minute stridulating weevil. (Natural size.) 



Fig. 3. Locusta viridissima, the Great Green Leaf-cricket, sm, Mirror of the 

 organ of stridulation ; t, mouth of the prothoracic spii-acle ; a, slit or rima on 

 the tibiaj. 



Fig. 4. A, Magnified view of Elaphrus riparius, right elytron and wing 

 removed, left elytron and wing expanded ; I, musical lima, b, Under surface of 

 right elytron, showing a protuberance, s, that acts as clasp to /. 



Fig. 5. A, Abdomen of a male cicada dissevered from the thorax and magni- 

 fied. The species [Cicada Plobeja, Oliv.) being cryptotympanous, or having its 

 drum-covers concealed by a lap of the dermis, this skin lap, c, has been cut 

 away from the left drum, so as to expose the ribbed membrane, t. To the 

 point indicated, p, the tendon t of the motor muscle m is attached, and by this 

 means the membrane is drawn inward during the music, the sound resulting 

 from its vibration on each rebound, d, Shows the diaphragm separating the 

 large internal air cavity ; s, the opening of the first abdominal spiracle ; m, 

 miiTors of the cicada, showing an iridescent spot of various colours centrally, to 

 which a little styliform thickening proceeds from their margin. The internal 

 aspect of this part, which has the essentials of an insect ear, is shown on Plate 

 VI., Fig. 5. B, Cicada Pleheja singing on an acacia spray at the foot of the 

 Superga Hills, near Turin. Motion of the abdomen indicated by a blur. Sketch 

 from nature, with the Alps in the background. 



Fig. 6. A magnified representation of iVi;'c?-oji)/?-o?vMV6'S7;J(!t^^o, a common Grave- 

 digger Beetle, with the left elytron removed. I, The lima ; s, the extremity of 

 the elj'tron that acts as clasp. 



Fig. 7. l-i A magnified view of the lima of Necrophorus vcspitillo (after Lan- 

 dois). 



Fig. 8. Illustration of the biology of the grasshoppers. 6, Males stridulating 

 in rivalry ; 9, female attracted by their music ; a, shows the lunate opening of 

 the organ of audition of Miiller and Siebold. (Sketched in the fields at Maida 

 Vale.) 



Fig. 9. Mutilla Eiiropea,&T[msiC3l^6\iidLrY A.vA. c5, Winged male ; 9, apterous 

 female. 



PLATE IV. 



ORGANS OF STRIDULATION AND AUDITION OF THE LEPIDOPTERA, ETC. 



Fig. 1. Organs of instrumental music of Vanessa lo, the Peacock Butterfly 

 I, The submedian or anal vein of the fore wing, or that nearest its inner margin. 

 Its filed aspect at the under surface of the wing when submitted to a strong 

 magnifying power is indicated, s, Costal vein of the hind wing, over which the 

 vein I plays its lima when the insect rubs its wings together in stridulation ; it 

 is prominent on the upper surface of the wing, sm, Shows a raised pucker at the 

 base of the hind wing devoid of scales, probably serviceable in impressing the 

 vibrations caused by the friction of the veins on the ambient air. Fig. 12 

 shows how the wings overlap at the basal point of friction, and illustrates the 

 contrast in the dark under and brilliant upper surface of the wings of this 

 butterfly. 



