I 



ECONOMIC ZOOLOGY ENTOMOLOGY. 255 



During the summer months all of the larvae hatching from a mass of eggs 

 usually die within 1 mouth after the first eggs hatch; in one instance, how- 

 ever, a period of 117 days elapsed from the beginning of hatching of the eggs 

 until the death of the last larva. Those larvse which succeed in finding an 

 animal engorge and drop from the host between the third and eighth days; 

 from 6 to 21 days then pass before they molt. Unfed nymphs have been found 

 to survive a period of more than 300 days. The nymphs, which require from 

 'I to 9 days for engorgement, emerge from about the middle of July to the 

 beginning of cold weather. Some of the nymphs which transform during the 

 summer find hosts and engorge. A few of these are thought to molt to adults 

 before cold weather begins, these individuals being the only ones which com- 

 plete their life cycle in a single season. 



Those larvae which hatch from eggs deposited by females that do not find 

 hosts until late in the spring become engorged during July and August and do 

 not molt to nymphs until shortly before winter. These nymphs begin to appear 

 in the spring, shortly after the adult ticks become active, the last individuals 

 not securing hosts until early in July. These individuals molt to adults during 

 the latter part of the summer, and the resulting adults pass the winter before 

 feeding. Thus it appears that although a few of the ticks may complete their 

 life cycle, from nymph to nymph, or adult to adult, during one season, the ma- 

 jority require 2 years. 



In considering the host animals of these ticks, tables are given which show 

 the results of examinations made of wild maihmals in the Bitter Root Valley 

 during 1910 and 1911, with the number and stages of D. venustus found 

 thereon, and of the animals on which D. venustus has been found in the adult 

 stage. Other species of ticks found in regions where Rocky Mountain spotted 

 fever occurs, species of ticks which might play an important part in the dis- 

 semination of the disease should it be introduced into new regions, and the 

 practical control or eradication of the spotted-fever tick are considered at some 

 length. 



Under methods of destroying this tick the authors discuss dipping, including 

 details of vat, construction, handwork, etc. The necessity for expert super- 

 vision in the work of controlling this tick is emphasized. 



A bibliography of the more important writings on the spotted fever tick, 

 consisting of 28 titles, is appended. 



The life history of a parasitic nematode (Habronema muscae), B. H. Ran- 

 som (Science, n. ser., 34 (1911), No. 881, pp. 690-692) .—This nematode parasite 

 of the house fly, first reported by Carter from Bombay, India, in 1861, was 

 recorded by Leidy in 1874 as occurring in 20 per cent of the house files examined 

 at Philadelphia. During the summer of 1910 the author found it to be fairly 

 common in house flies caught at "Washington, D. C-, and in 1911 to be com- 

 monly present in house flies in Colorado and Nebraska. 



Investigations which led to examinations of the stomachs of 2 horses in 

 1911 resulted in the finding of a complete series of stages in the development 

 and growth of this parasite from larva to adult. The embryos, which are 

 excreted in the feces, enter the bodies of fly larvae, developing therein from 

 eggs deposited by house flies. " During the development of the fly larvae and 

 pupae, the worms with which they have become infested also undergo a process 

 of growth and development, reaching their flnal larval stage at about the time 

 the files emerge from the pupal state. Further development of the worms 

 waits upon the swallowing of the infested flies by a horse, in which event the 

 life cycle becomes completed by the growth of the worms to maturity." 

 24971°— No. 3—12 5 



