186 LIFE HISTORY OF NORTH AMERICAN TICKS. 
The nymph (Tables LXXXV-LXXXVIT).—The longevity of the 
nymphs of this tick is shorter than that of any other species of Der- 
macentor studied by us with the possible exception of those species 
which molt on the host. The records made indicate that during the 
hot summer months the longevity ranges between 40 and 60 days. 
The greatest longevity observed was between 76 and 108 days. This 
record was made in the fall months. These nymphs were kept in glass 
tubes with cotton stoppers on moist sand in the laboratory. It is 
probable that during cool weather a somewhat greater period of 
longevity would occur. 
TaBLE LXXXV.—Longevity of nymphs of Dermacentor occidentalis. 
Number 
Date larve molted to nymphs. Number. nel on All larve dead. gate 
ost. ; 
1910. 1910. Days. 
TMNG ABE oe Ne oASo eek ees see eeeeee 37 Onl tulyTSitoyAueraee see cess 40-61. 
MUITNO 2124 Me cee eoceeies seaman dee 18 0} Aug. 4to Aug. 12............| 41-52. 
AFL gel WE 0 pele eae iies Sree etme ee Aa 300 230 | Aug. 12 to Sept. 24.......... 23-69. 
July/SUto re ie ee at nce eemee es 4 0) ‘BeforeiOch26 2 5--255---4--- Less than 75. 
PANTO il {ian Se me eee eee. ee 1 On Sarre GOS ers edenee csc eeemeee Less than 70. 
NODES GLO ie Hae oo etic ccs eects 10 0" | Nov, 200 Dees 23)... 2252 eee 76-108. 
TABLE LXXXVI.—Engorgement of nymphs of Dermacentor occidentalis. 
By uphs ed Dette fol- | Total 
owing application. num- 
D hs Num- 
pete els S Host. ae re State of engorgement. 
3 | 4°)-50) 6.127 1|-8.) 90 | meee 
1910. 
Sly Qo pe see Guinea pig..-.} (?) Sal Sal oul seaal eee sales 20 | Fully. 
Suiliy: 2655 ees Ses (Meee dome sec SOUS. eaeeilectes Cha Pain Tat es Lat 10 | One-fourth to fully. 
Tulys0s waseeeeeteee Bovine... ---- AP eee eel sic 1 ees bere ete 1 | One-third. 
PANTER GSTS. See abbit.s-e- ase 200! | Sa eLD aS 2e ELS) | Sates 2 72 | One-half to fully. 
PANTIE. Ould ee ae 2 Guiness, pigs = SiG?) lee neleeee DEN RS ANS Shieh all ap eS 2| Fully. 
1 These lots were accidental infestations, hence the exact date of attachment is not known. 
The shortest period of engorgement accurately observed was 4 days; 
the longest, 9 days. In the last instance the nymphs were still only 
about one-half engorged and were probably scratched off by the host. 
The weighted average engorgement period of all nymphs upon which 
accurate records were made is 5.56 days. Attachment was observed 
to take place, in most cases, almost immediately after the ticks had 
been placed on the host. 
