170 LIFE HISTORY OF NORTH AMERICAN TICKS, 
to hatch from the first eggs deposited some time before deposition is 
complete. 
Ordinarily larve attach within a very short time after they are 
applied to a host. However, we have observed them to remain 
unattached for three days when kept in close proximity to a host. 
The majority of the larve attach around the head and ears of the 
hosts. They are, however, frequently found on the back, especially 
between the shoulders. Larvze when removed from a host when 
slightly engorged were found to attach to another host several days 
or even weeks later. ; 
In a number of instances larvee which had awaited a host for 
two months were found to attach when placed on a host, but many, 
and in some cases all, died without engorging owing to their weakened 
condition. 
The shortest period required for the engorgement of larve was 
two days. The greatest number drop from the host on the third, 
fourth, and fifth days after attachment. In two cases larve 
remained on the host for 8 days. 
TaBLE LXXVII.—Engorgement of larve of Dermacentor venustus. 
Larve dropped engorged—days following appli- 
cation. 
Date larve applied. Host. pias Sihck ve NET SSE EM eee: ly eee ae number 
1 2 3 4 5 6 7 8 i Ree 
1908. 
Marebig0c vac. tae c ce eee nee Bovine........ 0 0 0 1 2 0 0 0 3 
BAST! iiss ee ets od ore Penal els ee Goes sas. 8 0 0 23 27 17 13 3 1 84 
IMA VSS Re Sos AesSicrcie cabin crenatera] SSeS GOtescweee 0 0 0 15 10 0 0 0 25 
ULV SSS eee Lae Sats se ese Goh. 2 bee 0 0 2 3 0 0 0 0 5 
Afiat vga) DSSS ee Me eaten Rae eels | Sees do. 0 0 76 64 12 4 0 0 156 
1909. 
DO ys28 2 see ot ate ccetee ae Guinea pig.... 0 0 0 0 6 2 2 0 10 
DWVi20 een saeees tace sae eae COOnn ee ciate 0 0 0 0 6 5 0 0 ll 
| DY ae Sas ae Bovine.......- 0 0 0 2 1 0 0 0 3 
HANI Din So etek So oe aE Rapbits.4-.\.-< 0 0 0 0 3 0 0 0 3 
UE. 4. occo eee sees cece eens Guinea pig 0 0 0 0 2 0 0 0 2 
Ondeet Ps aasess ces Eh. Bovine: c: 0 0 0 1 2 0 0 0 3 
PRUE S Lie. oes fine: oo eee eesleseos Gos: St se. 0 0 0 1 0 0 0 0 1 
1D 0 ha Sena Repeat en Se Guinea pig 0 0 0 0 0 1 0 0 1 
INE Dols Sew noe oeeee stats o's Ss Lee dOseaonaece 0 0 0 0 23 23 2 0 48 
AUP DT. LEO Aes ss. S54] ees Gor Fe yt: 0 13 26 58 56 23 5 0 181 
When the mean temperature was about 83° F. larve were found 
to become quiescent in from 24 to 60 hours after dropping. Immedi- 
ately after becoming quiescent the tick begins to take on a light 
color at the anterior end. 
Larve which dropped September 1, 1909, began molting on the 
sixth day thereafter. This was the shortest molting period observed. 
The mean temperature during the period was 88.29° F. and a total 
effective temperature of 272° F. was accumulated. The longest 
period from dropping to molting observed by us was 19 days. The 
mean temperature during this period was 70.5° F. The effect of 
temperature on the length of the molting period is marked. When 
the mean temperature was about 70° F. molting began between 
