NORTH AMERICAN LEPIDOPTERA. 103 



very much lengthened, becoming nearly or quite ten times as long as 

 the end memjier. More rarely the end member is lengthened, so as 

 to be nearly as long as the middle member. The shape of these 

 members also varies ; generally the middle member is flattened, cy- 

 lindrical, even ; sometimes, however, it is more or less triangular, 

 considerably flattened, and often grooved on the inner side. The 

 end member is ordinarily filiform, cylindrical, but it is often oval, 

 sometimes oval conical. The vestiture of these oi'gans varies in the 

 quantity and length of the scales, differing very much in the different 

 species. There is also some, but not very decided variation in these 

 oi'gans, in the sexes of the same species, though generally the sexes 

 nearly agree. 



Maxillary Palpi. — The maxillary palpi are very variable in 

 form and ornamentation. There are also often very marked 

 sexual differences. Ordinarily, if not always (I have found no ex- 

 ceptions so far as my studies have gone), they are four-jointed, the 

 basal joint being small and difficult to make out, except in well 

 bleached specimens, and with a compound microscope. The maxil- 

 lary palpi are generally comparatively small, more or less concealed 

 by the labial palpi, generally projecting forwards between the labial 

 [)alpi, rarely rising above them. In many species the last two mem- 

 bers are clothed with long hairs, giving a brush-like appearance. 

 These are capable of expansion, but ordinarily lie concealed in a 

 groove on the inner side of the second member of the labial palpi. 

 So far as my observations go, the maxillary })alpi are always present, 

 though often very small. In properly bleached specimens, and with 

 the use of a compound microscope, I have never found them absent 

 in the many species I have examined. My examinations, however, 

 owing to a lack of material, have not covered as yet all the American 

 species. 



The shape of the maxillary [ialpi varies oftentimes in the different 

 .sexes. When they do not differ, and in the female ordinarily, the 

 basal joint is short cylindrical, the last three oval cylindrical, each 

 one being on the extreme end or point of the one next below. In 

 the case of the brush tufted maxillary ])alpi these are found fully 

 developed in the males onl}', though there is generally in the females 

 of the same species a more or less apparent tendency in the same 

 direction. In the full development the first and second members 

 are long, filiform, elbowed with each other when at rest, capable of 

 being extended in a line with each other at the will of the insect. 



