NO. 1361. REVISION OF AMERICAN SIPHON AFTER A— BAKER. 369 



find fieiis of the o;cnu8 PkLx niuch iiioro nciirl}' rcljitcd to 1\ irritmis 

 than cvcMi the eat and dog- flea, livinj^' on rats and mice and other .small 

 rodents. Dr. Diiges had found, a number of years ago, one such 

 species to be abundant on a spermophile in Mexico. Later I liad 

 several letters relative to this matter from Dr. Lutz. director of the 

 bacteriological laboratoiy at Sao Paulo, Brazil. He outlined briclly 

 the importance of the facts to be determined, and sent material of tlu^ 

 greatest significance — t3'pical Pule.i' from rats and mice. We shall 

 look with great interest for the full elucidation of this subject hy the 

 exptn'imental Avork from Dr. Liitz's lal)<)ratorv. 



As to the other tropical regions we know practic-ally nothing. 1 

 have no records of fleas from India. However, from Asia noi-th of 

 India come true PuJex from the smaller rodents, and from the island 

 of Socotra we have Pulex padldus described as occurring on Jfun 

 albipes, so that we may expect to find true Pulex on rats in the Indian 

 region. 



ANATOMY. 



The classical works of Karsten, Landois, and Berte covered the 

 gross anatomy of the Siphonaptera very fully. It has remained, how- 

 ever, for Wagner and Rothschild to examine into the more minute 

 details and more especialh' from the comparative point of view. 

 Indeed, in comparative anatomy the work has just begun. The 

 facts relative to the anatonn^ of fleas will not ])e recapitulated here as 

 they are referred to extensively in the accounts of families, genera, 

 and species. It may be well, however, to refer to cei'tain special 

 usages in the classification of the group. 



Kolenati paid almost no attention to cha^totaxy in his works, some- 

 times scarcely giving a clear account of the ctenidia. Taschenberg 

 was far clearer in that respect. Wagner and Bothschild have attached 

 to it an importance equaling that it bears in the Diptera. and \-erv 

 properly so. Jn the present paper the term "spines" is applied to 

 the ctenidial armature, and to the larger members of the leg and 

 body armature; those of medium size are termed l)ristles and this 

 includes most of the body armature; the finest and flexi})le ones are 

 termed hairs. A few minute teeth often occur on the hiiul margins 

 of some of the doi-sal segments. Some of the bristles ai-e, in geneial, 

 very constant in position, notably those on the gena', hind margin of 

 head, and abdominal segments, except the last. Others are very \ aii- 

 able in position among the \arious species and conse<|uently very use- 

 ful in classification, especially those on hind margin of antennal groove, 

 vertex (this term here applied to that portion of head buck of antennal 

 grooves), last abdominal segments, genital organs, femora, lil)ia'. and 

 last joints of tarsi. The numl)er of ctenidial spines on the head is 

 usually very constant in any one species, while the number of spines 



