OVARIOLE NUMBERS IN SCARABAEOIDEA (COLEOPTERA: LUCANIDAE, PASSALIDAE, SCARABAEIDAE)^ Paul O. Ritcher Department of Entomology, Oregon State University, Corvallis, Oregon 97331 Charles W. Baker Department of Biology, Boise State University, Boise, Idaho 83725 ABSTRACT — Ovariole numbers were determined for 4 genera of Lucanidae, 4 genera of Passalidae, and 65 genera of Scarabaeidae. Lucanidae had ovariole numbers of 6-6 and 12-12; Passalidae had only 2 ovarioles in each ovary. The most common ovariole number in Scarabaeidae was 6-6. Ovariole numbers ranged from 1-0 in Scarabaeinae to 14-25 in each ovary in Pleocoma, thought to be a relict form. An ovariole number of 12-12 occurred in one or more genera of Dynastinae, Rutelinae, and Cetoniinae. Although ovariole numbers usually rep-resent a derived condition associated with egg laying habits and special features of each species' biology, there is still considerable indication of relationships between the groups. In 1961, Robertson published a summary paper dealing with ovariole numbers in Coleoptera which combined his original findings with those of previous workers. He reported that within 329 species in 45 families ovariole numbers varied from one to several hundred. Robert-son mentioned the single ovariole characteristic of Scarabaeinae (Cop-rinae) but concluded that there was remarkable uniformity in ovariole number in the Scarabaeoidea which usually had 6 ovarioles in each ovary. His data, however, shows 12-12 ovarioles in Lucanidae and 2-2 ovarioles in Passalidae, based on observations of only one species in each family. Halffter and Matthews (1966), attributed the extreme ovarian re-duction found in Scarabaeinae to nidification behavior. They reported that a single ovary with one ovariole was also present in Canthon virens Mann, and in two species of Onthophagus. There is considerable information in the literature concerning grass-hoppers (Orthoptera) and Drosophila (Diptera) that ovariole num-ber is controlled by genetic factors ( Blackith and Blackith, 1969; Rob-ertson, 1957; and Tessier, 1963 ) . For example, Robertson ( 1957 ) found that artificial selection in a strain of D. melanogaster for low ovariole numbers led to about a 14% reduction; selection in the other direction increased ovariole number by more than 50% and was still increasing after 10 generations. There is also evidence that ovariole number in ^ This investigation was supported in part by Grant GS-31129 from tlie National Science Foundation. Oregon Agricultural Experiment Station, Technical Paper No. 3895. 480
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