46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



wings. Quenther believes that the sense scales are wind tactile organs, 

 used in orientation. With the aid of them Freiling believes that night- 

 flying Lepidoptera in their rapid movements are able to avoid obstacles. 

 In regard to tactile hairs on the codling moth, all parts of the 

 integument were not searched for them and in most cases where found 

 they were identified from external appearances. Most of the tactile 

 hairs on the wings seem to be ordinary sense hairs (fig. 4, A, St), but 

 a few sense scales (Ssq) were seen. On the legs, maxillae, and labial 

 palpi sense hairs (fig. 5, A and D, St) and sense bristles (Sea) are 

 more or less numerous. On the antennae are found numerous sense 

 hairs (fig. 3, St), sense bristles (Sea), and end pegs (Ss). The large 

 non-innervated scales (fig. 3, G, SJi) overlap one another like shingles 

 on a roof and on some segments they cover nearly all the sense organs. 

 The peculiarly shaped pegs found on the maxillae (fig. 5, D, Pg and I) 

 are also to be classified as tactile organs. Some of the tactile hairs 

 on the antennae and mouth parts of codling-moth larvae are shown in 

 figures 9 and 10. 



V. GEORECEPTORS 

 I. BALANCING ORGANS 



When an animal responds to gravity a special static or balancing 

 organ is not necessarily involved, but such organs are known in four 

 Phyla — Ccelenterata, Mollusca, Arthropoda, and Vertebrata. Semi- 

 circular canals occur in the vertebrates, while otocysts or statocysts 

 are found in certain medusae, molluscs, and crustaceans. A statocyst 

 may be an open or closed cavity, lined with sense hairs. In the center 

 of the cavity may be one or more concretions of carbonate or phosphate 

 of lime, called otoliths or statoliths. In the shrimp a statocyst is found 

 in a segment of the claw. It is an open sac in which the shrimp 

 places grains of sand. As the animal moves about in all directions, 

 the grains of sand fall against the sense hairs thus enabling the shrimp 

 to keep its equilibrium. A statocyst, therefore, is nothing more than a 

 special touch organ, and the same may be said about the semicircular 

 canals in which the liquid in them takes the place of the statoliths. 

 A good review on this subject is by Dahlgren and Kepner (8, pp. 207- 



215)- 



Insects so far as we know do not have organs similar in function 

 to the semicircular canals and statocysts ; nevertheless, they certainly 

 have great balancing powers. The only case in which such organs 

 have been surmised is in the Diptera. The so-called balancers or 

 halteres were formerly considered organs of equilibrium, but flies can 

 fly just as well without them. 



