Summary: Attachment sites, phenology, and growth of larvae of Eylais sp. (Acari) on Dytiscus
alaskanus J.Balfour-Browne (Coleoptera: Dytiscidae)
R. B. AIKEN
Department of Entomology, Universih of Alberttr , Edmonton, Alttr ., Cantrdtr T6G 2E3
Received July 16, 1984
AIKEN,R. B. 1985. Attachment sites, phenology, and growth of larvae of Eyltris sp. (Acari) on Dvti.sc~u.sa1a.skcrnu.s J.
Balfour-Browne (Coleoptera: Dytiscidae). Can. J. Zool . 63: 267-27 I.
Larvae of aquatic mites are common ectoparasites of aquatic beetles. A population of Dyti.sc*u.scr1tr.skanu.s (Coleoptera:
Dytiscidae) studied in a central Alberta lake was parasitized by members of the genus Evlais (Acari: Hydrachnellae). Mites
attached preferentially in the costal-subcostal region of the ventral surface of the hindwings. Afferent blood flow in the costa
and subcosta and the numerous blood sinuses in this region provide an abundant food source. The smallest (=youngest) larvae
were taken on the first beetles caught in early spring, indicating that some mite larvae overwinter on the host. Mites grow
rapidly, reach maximum size in late June and July, and then enter the nonparasitic phase of the life cycle. Rates of parasitism
(proportion of beetles with parasites) was highest in early spring, declined throughout the summer, and rose again in the fall.
In this way, the parasitic phase of the mites life cycle occurs at the same time as the peak in the population of adult beetles.
'There was constant recruitment throughout the year into the population of larval mites indicating asynchronous cohorts or more
than one mite species.
AIKEN,R. B. 1985. Attachment sites, phenology, and growth of larvae of Eylcris sp. (Acari) on Dvti.sc~u.so1n.skanu.s J.
Balfour-Browne (Coleoptera: Dytiscidae). Can. J. Zool. 63: 267-27 I.
Les larves d'acariens aquatiques sont des ectoparasites communs chez les colCopttres aquatiques. L'Ctude d'une population