E:\TO~LOLOGlCAL SO('. OF BRITISH COLl; :.\Wi.\, PROt:. (1946), VOL. 43, FEll. 4, 1947

LOCAL ABUNDANCE OF THE WASPS ATRATUM AND MEGASTIZUS UNICINTUS (: and Bembicinae) 1

H UGH B. LEECH Dominion Forest Laboratory, Vernon, B.C.

On August 22, 1945, a small box con­ groups of from six to twenty, mostly on taining live wasps was received from Frank the seed heads, but extending for some dis­ Choveaux of Okanagan Landing, B.C. It tance down the upper stem. At 7 :30 p.m. contained two species, one a black bembi­ they were quiet, and easily captured. When cid with all orange-red band across the picked up in the fingers the male M egasti­ abdomen, the other a blackish sphecid. 'Zus gave a most realistic show of stinging; These were subsequently identified b~' G. the long spikes of the trident at the end of S. Walley as .114 egastizus unicinctus (Say) the abdomen were extruded, and the center and C Morion (Priononyx) ntrntu ill (Lt:: · one pressed against my skin strongly Peletier), respectively. enough to be felt-and what was worse, According to an interesting account of it looked just like a sting. The simulated the habits of these species by H. E. Smith attack was psychologically effective and I (1915. The grasshopper outbreak in New found it hard not to drop the insect hur­ Mexico during the summer of 1913. U.S. riedly. Dept. Agric. Bu!. No. 293, 12 p., 2 figs.), The wasps were often 'in mixed lots, C. (P.) atrntum is an important grasshop­ though in anyone group each species per parasite, stocking its nests with nymphs. showed a preference for its kind, e.g., Many of the burrows are re-opened by l11. where M. unicinctus were present they unicinctus females, which destroy the usually made up at least 75% of the total CMorions' eggs and replace them with on that grass head. Howe\'er, in all, the their own. Despite extensive outberaks of C hlorion outnumbered the M egastizw by hoppers in British Columbia, there is no nearly three to one. Of several hundred record of the wasps occurring here in num­ M egnstizus examined, all were males. bers. Only a single female was present in a ran­ Mr. Choveaux reported hundreds of the dom sample of 230 C. atratum: this de­ wasps to be congregated on heads of grain spite the lateness of the season, shown by and grasses each night, and he wondered if the fact that the wings of many of the they might damage the seeds. That eve­ Chiorion were faded and had ragged edges. ning we visited the area concerned, a field Indeed on September 5, by which time the about 3 miles from Vernon, just below wasps were scarce, the proportion of the the upper Landing road and west of its two species was still nearly three to one, junction with the Commonage road. and again all M egastizus were males and Grasshoppers were abundant; 1945 was only a few CMorion females were found. the third successive year of an outbreak of I did not discover where the females of M elanoplus mexicanus mexicanus (Sas­ the two species spend their nights. They sure) (det. 1. J. Ward). Mr. Chouveaux were not on the ground or under stones said that though the blue Chlm'ion was and trash; neither were they roosting on present but rare in previous years, the /11 c­ grasses or bushes within a quarter of a mile gastizus had not been on his farm before. of where the males congregated. Perhaps A few strips of tall grasses had been left the heavy clay in the field was unsuited for when the seed crops were cut, and 011 the burrows, and the actual nesting site was in tops of these grasses black clusters of the wasps could be seen from a distance of lighter soil some distance from the roosting several hundred yards. They were in grounds. A few male wasps were seen in tall weeds aloiIg the fence line and road­ 1 Contribution :\0. 2417, Division of Entomology, Science Servjce. Department of Agriculture. Ottawa, side bordering the field, but no other roost­ Canada. ing ground was visible.