156 
Biology of Dermacentor 
sheep and sent to Dallas, Texas, were kept in a sack on the scrotum of 
an angora goat for three days, but neither became attached; but 
when they were placed upon a guinea-pig they attached themselves 
immediately. 
Seasonal History. 
All the information which we have regardiog the seasonal history 
of this tick is our records of collections, all of which were made by 
Mr George S. Hutson, of Quartzsite, Arizona. These lots were collected 
in July, August, September and December. The collections indicate 
that most of the females become engorged and drop off the hosts 
during the fall and winter. All the following records were made at 
Quartzsite, Arizona : 3 </ (a dozen or more specimens, probably not 
engorged, were collected, but not sent in), July 8, 1910 ; 16 </, 1 $ 
(unengorged), August 10, 1910 ; 5 J 1 , 2 $ (unengorged to en ' 
gorged), August 20, 1910; 18 13 $ (unengorged to fully engorged), 
December 1, 1910 ; 23 f , 12 $ (unengorged to engorged), September 
2, 1911. Several specimens, mostly males, escaped when the last col¬ 
lection was being made. 
Life History and Habits. 
Oviposition: No records have been made under natural conditions 
on the pre-oviposition period. Two females Q and well engorged) 
taken from a host December 1, 1910, were received at Dallas, Decem¬ 
ber 7, and put into an incubator at a mean temperature slightly above 
90° F. These began to oviposit about December 11, and completed 
oviposition in nine days, having deposited about 1000 and 2500 eggs 
respectively. The eggs are deposited in masses as in other species of 
Ixodidae. 
The process of oviposition was not observed, but an engorged female 
was seen extending and retracting the vesica biloba 1 , though no eggs 
were laid. She afterwards died without ovipositing and with the vesica 
biloba extended. This organ does not differ materially in structure or 
appearance from that observed in other ticks. When the lobes are 
extended they appear like tapering fingers, the tips being curved 
ventrally so as to rest on the dorsal surface of the basis capituli or palpi, 
according to the distance they are extended. They are transversely 
wrinkled. The basal part of the organ is distinctly bilobed dorso- 
1 Termed Gene's organ by Nuttall 1908; see also Robinson and Davidson (iv. 1913), 
Parasitology , vi. 34, and their paper appearing in the next number.—Ed. 
