The morphology of the sensory receptors on tarsus I and on the mouthparts of the cattle tick Boophiitis ~~i c r o p h r s were examined by means of scanning electron microscopy. Features not resolved by light microscopy were revealed. The number of seiisilla and their morphology are unique to B. tnicrophrs though similar to those of other tick species already described. The sensory setae found include mechanoreceptors, contact and olfactory chemoreceptors. Of s p e c~l interest, on each inner cheliceral digit, is a denticle beuriiig a papilla at its tip and a pit at its base. The functions of these two newly describcd features are not known but it seems likely that they may include contact chcmoreceptors capable of tasting host tissue chemicals. These observations provide the foundation for transmission electron microscopy of the receptors. which is the subject of the third paper in this series.
IntroductionScanning electron microscopy (SEM) has been used to study the morpholog: of sensory receptors on the lone star tick A171h/yo171171~1 C I M Z~Y~C C I I Z~~~W (L.) (Bruce 1C 71, Foelix and Axtell 1971, Foelix and Chu-Wang 1972, Chu-Wang and Axtell 1972, 1973, 1974) and on other Ixodid and Argasid species (Axtell et 01. 1971, Sixl et (11. 1971, Roshdy et a/. 1972. Sixl and Nosek 1974. Apart from the brief account of Chow and Wang (1975) this technique has not been used for detailed studies on the sensory receptors of the cattle tick Boophiliis micwplus (Canestrini) Ixodidae. A simple scheme for naming and numbering the sensillti of B. nzicruplrrs has been presented (Waladde 1976). In this study the scanning electron microscope has been used to show their structure in greater detail, thus indicating more clearly their possible functions and providing a basis for transmission electron microscopy and electrophysiological studies. The ultimate purpose of this work is to reveal the functions of the sensory iieuroiies innervating each sensillum. This information will facilitate a rational interpretation of tick behaviour.
