OF WASHINGTON, VOLUME XI, 1909. 109 



Dr. Dyar stated that while the larvae of the species of Hylo- 

 taina were distinct, the adults were hard to distinguish, and re- 

 ferred to an article by himself (Journ. N. Y. Ent. Soc., v. 

 IS, 1X07), in which five different types of Hylotouia larvae pro- 

 duced a jumble of different adults. Further study of tin- 

 species is badly needed. 



Dr. Hopkins thought that this species might become a serious 

 pi-st, especially if it should work on other species of willow, 

 such as the basket willow. * 



Mr. Hooker presented the following paper: 



NOTE ON AN EXTRA NYMPHAL MOLT OF ARGAS 



MINIATUS. 



[Acarina, Argasidae.] 

 BY W. A. HOOKER. 



As an introduction to the observation which I wish to record, 

 a brief account should be given of the molting habits of the 

 ticks. As is generally known by entomologists, in order to 

 develop it is necessary for ticks to engorge blood. Immature 

 ticks molt following each meal of blood. Ornithodoros sai'ig- 

 nyi and O. moubata, two African species, the latter of which 

 transmits human tick fever, are exceptions, however, as both 

 are inactive in the larval stage and pass the first molt before 

 ingesting blood. While there is no evidence that ticks develop 

 through feeding upon plant juices, as do some of their near 

 relatives, the possibility of which has even recently been con- 

 sidered by one investigator, .it is undoubtedly true that they 

 (at least the Ixodid ticks) imbibe more or less moisture. With 

 the exception of Ornithodoros mcunini, it appears to be neces- 

 sary in order to oviposit that blood be engorged following the 

 last nymphal molt. 



While the Txodid ticks pass but two molts (larval and nym- 

 phal) during their life, there appears to be a difference in the 

 number passed by the Argasids. In the genus Ornithodoros, 

 while nicgniiii passes but two molts before arriving at the adult 

 stage and none afterwards, sark/nyi and moubata appear to 

 have three or more, and the latter is reported to continue molt- 

 ing as an adult. Whether there is a variation in the number of 

 nymphal molts in each of these two latter species, however, 

 does not appear to have been determined. The species of the 



