1919] Mclndoo: Olfactory Sense 77 



none on the tarsi of 2 species (Nos. 14, 15). The number of 

 pores found on the first thoracic segment varies as follows: 

 Six on each of 2 species (Nos. 7,8); 4 on each of 2 species 

 (Nos. 20, 22) ; 3 on each of 2 species (Nos. 9, 23) ; and 2 on each 

 of 5 species (Nos. 10, 12, 24, 26, 27). Two pores were found on 

 each of the last abdominal segment of 3 species (Nos. 7, 8, 13). 

 The number of pores on both anal prolegs varies as follows: 

 One for each of 3 species (Nos. 5, 22, 23) ; 2 for each of 2 species 

 (Nos. 12, 13) ; and 4 for the army worm (No. 8). 



The total number of pores found varies from 61' to 102, but 

 no conclusion in regard to the comparative sensitiveness of the 

 various species can be drawn, owing to the fact that only one of 

 the species listed was critically studied. 



In these examinations no attention has been paid to the 

 size or age of the larva being examined and at first thought one 

 might think that the disposition of the pores would vary 

 according to the instars, but Mr. Busck informs me that he has 

 found no such variations. 



Discussion. According to the earlier papers concerning 

 lepidqpterous larvae, some of the entomologists have observed 

 the more conspicuous pores on the heads of these larvae; they 

 have called these organs sensory pits and punctures, but knew 

 nothing about their internal anatomy. Within the past few 

 years, systematists have been making comparative studies of 

 the setae and punctures present on the integuments of lepidop- 

 terous larvae and have used these characters successfully for 

 classifying the larvae. 



Forbes (1910) seems to have presented the first comparative 

 paper on this subject. He appears to have found some punctures 

 on all of the larvae examined; he has mapped the frontal 

 punctures on 33 species and adfrontal ones on 28 species, but 

 represents only a few of those present on the epicranium and 

 mouth parts. The same author (1911) mapped 3 pairs of punc- 

 tures on the labrum each of 4 sphingids. 



Tsou,(1914) mapped 2 pairs of punctures on the dorsal sur- 

 face of the prothorax of two genera. 



Fracker (1915) mapped the frontal and adfrontal punctures 

 of several species. 



Heinrich (1916) named and mapped most of the punctures 

 present on the head capsule of a micro-lepidopteron, and the 



