SENSE-ORGANS IN Till': H'lXf.'S AND BALANCERS 293 



ulty of the perception of the direction of sound more highly devel- 

 oped than in any other class of animals." (Also see Child's work.) 



Special sense-organs in the wings and halteres. Organs of a special sense, 

 which Hicks supposed to be those of smell, were found by him near or at the 

 base of the wings of Diptera, Coleoptera, and less perfect ones in Lepidoptera, 

 Neuroptera, and Orthoptera, with a trace of them in Hemiptera ; but these 

 were considered by Leydig to be auditory organs, since he found the nerves to 

 end in club-shaped rods, like those of Orthoptera. 



Hicks found, as to the halteres and their sense-organs, that the nerve in the 

 halter is the largest in the insect, except the optic nerve ; and that at the base 

 of the halteres is a number of vesicles arranged in four groups, to each of 

 which the nerve sends a branch. Afterwards Bolles Lee discovered that the 

 vesicles, undoubtedly perforated, contain a minute hair, those of the upper 

 groups being protected by hoods of chitine. He regarded them as olfactory 

 organs, while Lubbock seems inclined to consider them as auditory structures. 

 Graber also regards the vesicles of Hicks as chordotonal organs. 



In his elaborate account of the balancers, Weinland concludes that the 

 organs of sense of varying structure occurring at the base of these appendages 

 allow the perception of movements which the halteres perform and which 

 enable the fly to steer or direct its course. The halteres can thus cause differ- 

 ences in the direction of the flight of a fly in the vertical plane. If the bal- 

 ancers act unequally, there is a change in direction. 



' . The sounds of insects 



Insects have no true voice ; but sounds of different intensity, 

 shrill cries, and other noises are produced mechanically by insects, 

 either being love-songs to attract the sexes, to give signals, to com- 

 municate intelligence, or perhaps to express the emotions. The 

 loud, shrill cry of the Cicada, or chirp of the cricket, is evidently a 

 love-call, and results in the mating of individuals of separate broods 

 more or less widely scattered, thus preventing too close inter- 

 breeding. 



The simplest means of making a noise is that of the death-watch 

 (Anobium), which . strikes or taps on the wall with its head or 

 abdomen. Longicorn beetles make a sharp sound by the friction 

 of the mesoscutellum against the edge of the prothoracic cavity, the 

 head being alternately raised and lowered. Burying-beetles (Necro- 

 phorus) rub the abdomen against the hinder edges of the elytra. 

 Weevils make a loud noise by rapidly rubbing the tips of the abdo- 

 men on the ends of the elytra. 



Landois offers the following summary of the kinds of noises produced by 

 beetles : 



1. Tapping sounds (Bostrycinse, Anobium). 



2. Grating sounds (Elateridse). 



3. Friction without special rasping organs (Euchirus longimanus). 



