Dr. Stafford Tick Management Handbook - Newtown, CT

StaffordThe capitulum in hard ticks is visible dorsallyin all stages. The capitulum holds the mouthpartsconsisting of a base (basis capituli), two palps,paired chelicerae, and the median ventralhypostome, which is covered with denticles orrecurved teeth. The shape of the basis capituli,length of the palps, number of denticles, and othercharacteristics of the mouthparts are used to helpidentify tick genera and species. While the adultsof some common ticks can be easily identi. ed witha little training because of distinctive markingsor color, the identi. cation of most ticks and theimmature stages requires the services of a trainedentomologist and the use of keys developed bytick taxonomists. These keys are designed tospeci. cally identify adults, nymphs or larvae.Above right: Mouthparts of I. scapularis nymphsshowing hypostome with rows of denticles (center) andtwo pair chelicerae (palps are partially visible).The Connecticut Agricultural Experimentation Station13How a Tick FeedsThe term tick bite may be misleading as ticksdo not bite and depart or feed rapidly like amosquito. Ticks attach and feed gradually overa period of several to many days. Once a tickhas found a suitable place to feed, it grasps theskin, tilts the body at a 45-60° angle, and beginsto cut into the skin with the paired chelicerae.The palps lay outwards on the skin surface. Afterthe chelicerae and hypostome penetrate the skin,they become encased in “cement” secreted by thetick. The cement serves to hold the mouthparts inplace while the tick feeds. Mouthparts on larvaland nymphal ticks are small with less penetrationand produce a smaller host reaction. Adult Ixodesand Amblyomma ticks have long mouthparts thatcan reach the subdermal layer of skin, producea larger reaction, and make the tick harder toremove. Insertion of the mouthparts often takesaround 10-30 minutes, but can take longer (1-2hours). The reaction to a feeding tick may makethe tick appear imbedded, but only the slendermouthparts actually penetrate the skin.1415Scanning electron micrographs of the mouthparts of the blacklegged tick (top) and American dog tick(bottom). On the top picture the two palps are spread apart showing the upper two chelicerae and the lowerhypostome bracketing the oral cavity.Bulletin No. 1010 7