ABSTRACT
The viruses are always observed in the cytoplasm where they have circular outlines 60 nm in diameter. Many viruses have been discovered in Arachnida but most of them, present in bloodsucking Acarina (ticks), are transmitted to a vertebrate host and belong to Arbovirus groups. Only six nonoccluded viruses are strictly associated with other Arachnida. Development of baculovirus-like particles takes place in large ovoid nuclei while morphogenesis of icosahedral virus occurs in regularly spherical nuclei. Morphogenesis of virions takes place principally inside viroplasms but some viruses appear on the surface of the virogenic stromata. These external viruses regroup to form an accumulation of regularly packed viruses. In the same way, viruses regroup in crystalline arrays inside viroplasms. The icosahedral virus is probably related to the Adenoviridae based on its morphology, size, and cytopathology in infected nuclei of susceptible tissues. A few icosahedral or rod-shaped virus-like particles have been observed in the European red mite and in the citrus red mite.
