C, H. TYLER TOWNSEND — BIOGEOGRAPHY OE MEXICO, ETC. 61 
• 5. Gymnosoma fuliginosa Desv. — Six specimens taken in the Mesilla 
Valley, at or near Las Cruces, at various times, in March and from Au- 
gust to October. On flowers of Prunus (March), Solidago canadensis 
(August), and Bigelovia wrightii (September and October). This species 
has never before been recorded from ISTew Mexico, or in fact from any 
part of the arid region; nor have the genus, or even the family, Gymnoso- 
matidae , to which it belongs. It was taken in the Sacramento Mountains 
(Rio Tularosa, 6200 feet), as already stated. It is comparatively rare in 
New Mexico, but is characteristically common in the humid Uppe r 
Austral — the Carolinian , which corresponds in the East to the Upper 
Sonoran. It is very common at Washington, D. C. It also occurs com- 
monly at Constantine, Mich., which is just in the northern edge of the 
Carolinian. I believe that it ranges well into the Austroriparian. Its 
especial abundance at Washington would indicate this, since that locality 
partakes largely of the Austroriparian fauna. 
On Trombidium. — It may appropriately be mentioned here, as bear- 
ing on the biogeographical position of the Mesilla Valley, that the pres- 
ence or absence of the irritating larval forms of Trombidium will be 
found to furnish data of much use in connection with the determina- 
tion of life zones. These mites, as. well as causing intense suffering to 
sensitive persons, are themselves very sensitive to climatic influences. 
Their comparative abundance when present, coupled with their seasonal 
duration, indicates much from a biogeographic point of view. They are 
commonly known to Americans as “redbugs” and “jiggers” (or “chig- 
gers”); to the French as “bete rouge”; and to the Mexicans as “colora- 
dillas.”* They are particularly bad in the Tropical , in green portions 
of the Lower Sonoran, and in the Austroriparian. They are present, 
but much less numerous and troublesome, and of much shorter seasonal 
duration, in the Carolinian and green spots of the Upper Sonoran. In 
tropical and semitropical latitudes, their seasonal duration lasts through- 
out the year, in the absence of frost and drouth. Farther north, their 
season begins from May to July or August, according to climatic condi- 
tions and latitude. From my own experience, I can furnish the follow- 
ing data: They are present at Constantine, Michigan, in August, but 
are not numerous. At Washington, D. C., they are very numerous and, 
in J uly and August at least, seemingly quite as bad as I have ever known 
them in the tropics; their season there lasts from May or June till frost. 
These facts alone show the strong tinge of the Austroriparian in the 
fauna at Washington (D. C.). They are very bad in southern Texas, 
southern Louisiana, Florida, Jamaica, the whole Atlantic coast region 
* These must not be confused with the pinolillos of Mexico, which are the 
minute newly-hatched ticks (Ixodidae).— C. H. T. T. 
