FNZ 4 - Eriophyoidea except Eriophyinae (Arachnida: Acari) - Life Cycle
Manson, DCM 1984. Eriophyoidea except Eriophyinae (Arachnida: Acari). Fauna of New Zealand 4, 144 pages.
(
ISSN 0111-5383 (print),
;
no.
04.
ISBN 0-477-06745-X (print),
).
Published 12 Nov 1984
ZooBank: http://zoobank.org/References/C249A0E0-4F66-431B-9DB6-5C01ACA8CF65
Life Cycle
Two main types of life cycle occur in eriophyoid mites. The first, sometimes called a simple life cycle, involves only one type of female. The female lays eggs, there are two nymphal stages, and finally the adults develop. The nymphs differ from the adult in being smaller (although the second nymph reaches adult size before moulting), in lacking external genitalia, and in the extent of body microtuberculation.
Ramsay (1958) studied the life cycle of Aceria victoriae, a species causing bud galls on Haloragis erecta. The sizes of the respective stages were: first nymph, 100-110 µm long; second nymph, 126-164 µm; and adult 170-220 µm. Ramsay pointed out that the microtubercles of the first nymph are somewhat irregularly arranged and widely spaced, becoming more regularly arranged and more closely spaced in the second nymph. The first nymph has 60-64 dorsal rings, reduced ventrally to about 35; the second nymph has 65-70 dorsal rings, reduced to 54- 60 rings ventrally; and the adult has about 70-80 closely spaced and regularly arranged dorsal rings, reduced to about 65-72 ventrally. Another feature he noticed was the differing position of the dorsal shield setae in the three stages. In the first nymph these are directed anteriorly; in the second nymph they are directed posteriorly and upwards; and in the adult, posteriorly. The duration of the life cycle was not stated. Hall (1967) states that a simple life-history cycle takes from 10 days to 2 weeks to complete.
The second type of life cycle, sometimes called a complex life cycle, involves two types of female: the protogyne or primary form, which is associated with males and structurally is very similar to them; and the secondary female or deutogyne, which is not associated with males and is quite different in appearance to the protogyne. Protogynes frequently occur on the leaves of the host plant, whereas deutogynes usually appear in response to leaf hardening or the onset of winter, and hibernate in bark crevices or lateral buds, emerging the following spring to lay eggs on the new foliage. These eggs give rise to protogynes and males. Deutogynes preserve the species during less favourable times of the year when food is not freely available.
Deutogynes and protogynes of a species may differ from each other so much that in the past they have been placed not only in separate species but even in separate genera. It is important both taxonomically and from a pest management standpoint to realise that deutogynes do exist, and that they usually have different habits from the protogyne.
In the New Zealand fauna there are species that are known to be deuterogynous, and where material has been available both protogyne and deutogyne are described. In the keys to genera and species, however, deutogynes have been ignored; only the protogyne form is referred to. The keys will not function for deutogynes.
In general, deutogynes can be distinguished from protogynes in the following respects:
- they usually have reduced microtuberculation or, where microtuberculation is complete, the microtubercles differ in shape from those of the protogyne;
- the dorsal shield usually has less ornamentation, and the anterior lobe is thinner and more downturned;
- rust mite deutogynes usually have narrower tergites and are without ridges, furrows, or other body projections.
Until recently it was considered that deutogynes occurred only on deciduous or partially deciduous host plants, but Keifer (1976) has described Phytoptus adenostomae as an eriophyid living on an evergreen host (Adenostoma fasciculatum) in California and yet having the two female morphs characteristic of deuterogyny.
Ten species of eriophyoid mite are known to have deutogynes in New Zealand, and two of these are from the evergreen Nothofagus menziesii - Aceria simonensis n. sp. and A. waltheri. In addition, Aceria titirangiensis is suspected of showing deuterogyny, and both Acalitus lowei and A. morrisoni are variable in structure, to a quite considerable extent in A. lowei.
Keifer (in Jeppson et al. 1975) states that the probable life span of an active protogyne is about a month or 5 weeks, and that new protogynes continue to develop as long as conditions are favourable.
There has been no study of the life cycle of deuterogynous forms in New Zealand.
I have made no detailed investigations of males in the course of this work, and simply state whether they are known to occur for each species. The keys deal solely with adult females.
The mechanics of fertilisation in the Eriophyoidea were not understood until recently, when work by Oldfield et al. (1970), Sternlicht (1970), and Sternlicht & Goldenberg (1971) showed the occurrence of spermatophores and the phenomenon of female self-fertilisation. Sternlicht & Griffiths (1974) studied the emission and form of spermatophores in Aceria sheldoni. Males lay down stalked spermatophores where females can find them; the female moves up over the sperm sac, and presumably squeezes the sperm from it by using the hinged coverflap (Sternlicht & Goldenberg 1971, Oldfield et al. 1972). There is no transfer of sperm by direct contact between male and female.