Randal Latta.
The Effect of the Extreme Temperature of Dec. 7, 8, and 9, 1927 on Hibernating Crioceris asparagi L. and Hippodamia convergens Guér. at Ames Iowa.
Psyche 35(4):229-231, 1928.

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19281 Effect of Extreme Temperature on Criocerus 229 THE EFFECT OF THE EXTREME TEMPERATURE OF DEC. 7,8, AND 9,1927 ON HIBERNATING CRIOCERIS ASPARAGI 1,. AND IYIPPODAMIA CONVERGENS
GTJER. AT AMES, IOWA
BY R,AXDALL LATTA
Ames, Iowa
During the early winter of 1927 at Amcs, Iowa, the tem- perature dropped suddenly on Dec. 6 from 26OF to7' the follow- ing day, to -25' on the 8th and then rose again to -8' on the 9th. A small amount of snow had previously fallen, but was mostly in drifts, leaving many places exposed. Field observations following this period proved that Hippo- damia convergens Guer., a common cowinellid and CGxeris as- paragi I,. the asparagus beetle, were not able to withstand this unusual temperature.
Hippodamia convergens is probably the most common cocci- nellid in the vicinity of Ames, Iowa. Large numbers of them, as well as lesser quantities of other species of ladybirds, gathered in late summer at a turnip patch on a truck farm at the outskirts of Ames, to feed on the aphids there. As fall advanced the beetles hibernated in the sod fencerow at the edge of the turnip field. In the latter part of December the above mentioned fence- low was examined and a 100% mortality found. In a space 6 feet long and one foot wide immediately bordering the turnip patch 26 dead H. convergm were counted. An open crevice of a fencepost held 50 dead ladybirds of this species, and between 50 and 75 dead specimens were removed from beneath a stone at the same place. At the same time living specimens of H. parenthesis, H. 13-punctata and CoccineRa 9-notata were found active among the dead H. convergezs.
Other observations made later supported the above findings. At a highland prairie northwest, of Gilbert, Iowa, nearly 40 dead H. comwgew were uncovered beneath stones, and at the time living H. 13-punctata and H. parenthesis were collected. In the spring of 1928, Hippodamia 13-punciata and H. pa-



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230 Psyche [December
renthesis were very common while H. comergens were scarce enough to be almost rare.
At the same truck farm, a large asparagus bed was heavily invested with Crioceris asparagi. These beetles hibernated early in such shelter as they could find: in the sud of the fencerow, hollow asparagus stalks thruout the bed, hollow weed stalks, in the burrows of the grape cane borer, smartweed borer, and even in company with a strawberry leaf roller larva in a folded straw- berry leaf.
After Dec. 10th an exhaustive survey of the asparagus bed revealed an almost total mortality, only six beetles being revived when warmed out of several hundred collected. The six were hi- bornating in a hollow asparagus stalk.
In the sod fencerow the beetles had hidden in the layers of decayed organic material found at the surface of the ground in most blue grass sod; but were never found in the ground. The first 12 or 14 inches of sod next to the asparagus sheltered the majority of the beetles that had thus wintered. As high as 83 specimens were counted in an area one foot square. The asparagus beetles had not been observed to bore into a stalk, nor had any evidences of frass been seen in the stalks ex- amined. Beetles had entered, usually, by the path of some pre- vious insect, or at a broken internode.
A number of stalks in lots of 50 were examined to dekrmine the number of beetles that had used such shelter, and in four lots the infestation ran 32%, 32%, 22%) and 52% with as high as 46 specimens in a single stalk.
Two species of Anthicida, Anthieus cervinus Laf. and A. amosnus Casey, were often collected in company with the as- paragus beetles and always showed activity upon being disturbed. Sanderson (Journal of Economic Entomology, Vol. I, 1908, pp. 245-262) plots on a map of the United States a series of iso- therms showing the average annual-minimum temperatures and the relation between the nort.hward limitation of certain forms and these isotherms. The average annual-minimum for central Iowa is -10'. The -25' of the past winter is therefore an ex- ceptional drop for this locality.




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19281 Effect of Extreme Temperature on Criocerus 23 1 The average annual minimum isotherm of -lQO bisects Iowa, crosses northern Illinois, cuts thru Michigan and includes the region of Ontario influenced by the lakes, cuts thru New York state and the center of New England. Allowing for seasonal de- viations of warm winters, etc., the beetle has hovered along this invisible barrier during its westward spread.



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