646 



ZOOLOGY 



rubbing of the femur of the last pair of legs over a series of ridges 

 on the anterior wing, and that of the Locust by the rubbing against 

 one another of the roughened basal parts of the first pair of wings. 

 In other cases the sound results from the rapid vibratory move- 

 ment of the wings ; this is the case with the buzzing of many 

 Diptera and Hymenoptera. Again, the humming sounds charac- 

 teristic of many of the last named order are produced partly by 

 the vibrations of the wings in flight, partly by the vibration of 

 leaf-like appendages in the tracheae set in motion by strong 

 expiratory currents of air. The loud shrill note of the Cicada is 

 produced by the rapidly recurring contractions of the fibres of a 

 muscle inserted into a stiff chitinous membrane, the result being 



Fio. 526.—^, female and S, male sexual apparatus of the Honey-bee ; atl, accessory glands ; 

 de, c jmiuon ejaculatory duct ; ffd^ poison-glands ; gb, poison-vesicle ; ks, bulb of the stinging 

 apparatus ; i/W, rectum, twisted back and cut off ; nva, accessory sac of the vagina (bursa 

 copulatrix) ; od, oviduct ; ou, ovary ; p, penis ; rs, receptaculum seminis ; sd, colleterial gland ; 

 t, testes ; va. vagina ; vd, sperm-ducts. (From Lang's Comparative Anatomy.'} 



a series of crackling sounds, which follow one another so rapidly 

 as to give rise to a continuous note. 



Reproductive organs. — The sexes are always separate in 

 Insects, as in Arthropoda in general ; and the males and females 

 are very commonly distinguishable from one another by various 

 modifications of form and of coloration. There are two ovaries 

 each of which consists of a greater or smaller number of narrow 

 tubes or ovariolcs ; in each of these the ova are arranged in a single 

 row- — the early stages in their formation being situated at the 

 anterior end, the more mature ova towards the posterior extremity. 

 Each group of ovarian tubes opens into a lateral oviduct, and the 

 two lateral oviducts, right and left (Fig. 626, A, od.), in most cases 

 unite behind to form a median oviduct or vagina {va.), which 

 opens towards the posterior end of the abdomen. Connected with 



