Aggregation of lady beetles on the shores of lakes (Coleoptera: Coccinellidae).By Lee, R.E., Jr.
Lee, R.E., Jr. 1980. Aggregation of lady beetles on the shores of lakes (Coleoptera: Coccinellidae). American Midland Naturalist, 104(2): 295-304.
ABSTRACT: Aggregations of lady beetles, predominately Hippodamia convergens
and H. tredecimpunctata
, were commonly observed on the shores of lakes in the Upper Midwest during the autumn and spring. The beetles remain on the shore for only a short time, usually dispersing within 2-3 weeks. Lady beetles from autumn shore aggregations and overwintering aggregations are characterized by the presence of large amounts of fat, reproductive inactivitiy, empty digestive tracts, a skew in the sex ratio favoring females and the behavioral tendency to form aggregations. Hippodamia convergens
, the most commonly observed coccinellid in shore aggregations, undergoes long migratory flights to and from overwintering sites in California. It is suggested that similar migratory activity occurs in the Upper Midwest and that during these flights the beetles may be blown into the water and washed ashore, thus forming the aggregations. However, in contrast with the overwintering aggregations in California, the shore aggregations reported in this study appear to be temporary shoreline collections and not the overwintering site.