VOL. LIII. GUELPH, MAY, 1921. No. 5 A. G. POPULAR and PRAC
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- - -- - -- _ --- -- -- - A -- - -- VOL. LIII. GUELPH, MAY, 1921. No. 5 - -- ------- - - - - - - - - -- -- -- - - _ --_- JOHN MXCOUN ME;\IORIAL. At the request of natulalists generally throughout Canada, the Ottawa Field-Naturalists' Club has decided to receive subscriptions for a permanent lne~llorialin honor of the late Prof. Jol111 SIacolul~.Naturalist of the Geological Survey of Canada, who died at Sidney, R. C., on July 18, 1920. The wide field of natural hisiory 1~0rlito which John Macoun devoted his life is well known, II~Lonly throughout Canada but in other countries as well. He specialized particularly in botal~yand was the founder of the Canadian Ka- tional herbarium. Other sciences, however, especially zoology, were also greatly enriched by him; he will always he remembered as a great pioneer in Canadian natural history. Many friends of the late John Macoun, particularly ill Toronto and Ottawa, have thought that the ~nemorialshould take the form of a painted por- trait to be hung in the Victoria Aleinorial J!Iuseuln. Such a inelnorial has now been decided upon and a painiitlg will be n~atleby Mr. Franklin Rrownell of Ottawa, the well-known portrait painter. Expenses in connection therewith wlll he about $70. Subscriptions to this fund should he forn~ardeclto Mr. Arthur Gibson, Dominion Entomologist, Ottawa. Should the ltst be oversubscribed arrangeinents may be made whereby those subscribing above a certain stun, which now cannot be defined, will receive a reproduction of the painting. A. G. POPULAR AND PRAC'STCXL ENTOMOT,OCY. PARASITESOF t17~r: PALE: \VI+S*I~~RN CUTWORRT IN AI,RERTA. BY F:. H. STRTCKL4ND, Entomological Branch, Ottawa." The pale western cut worn^, Porosngrotir orlliogop~iaMorr., has been, since 1911, the most destructive insect pest of grain crops in southern Alberta and in a small area of south western Sasltatchewan. The damage in some years amounts to con<iderably over a million dollari, and all control measures so far employed have provcd to be unsuccessful when they are applied to large areas of infestation. For this reason natural control is of superlative importance. The larvz of this specie; are almost entirely whterranean in their habits, and they are never seen above ground by daylight. Hence they are practically immune from destruction by the all too scarce prairie birds. Some fall prey to prexors such-as Calosolrza friyidum Kby and A~~~~i~o~lzilaspecies, but these re- present a very small percentage. No signs of diseaje have been observed, the *Contribution from the EntomologicaI Branch, Dept. of Agriculture, Ottawa 97 9 8 THiE C&NAI)IAN ENTOMOLOGIST winter is passed in the egg stage which appears to be little affected by freezing, and the larvz cannot be drowned, even with excessive irrigat,ion. Although the species occurs throughout the Great Basin region of the United States, in which it is recorded from five States, it has never appeared :here in destructive numbers. Receiltly it has increased in Montana to an alarrn- ing extent. I11 the hfontana iigricvltural Station Circular No. 94, (1920) the state- ,,lent is lnade the "pale .,ve;tel-n cut\vorin, remaining as it does below the face of tile grou1~d,is protected from the attacks of parasitic insects." The ab- selice of parasite; in this qxcies in Moi~tanahas been commented upon in cor- respolldeilce to the writer both by Professor Cooley, ant1 Mr. J. R. Parker. 'I'his colldition is very much at variance with that experienced in Alberta, where parasites are of great il~q~ortance,and significance. We are able, in most seasons, to predict the of outbreaks 11y a sttldy of the parasite conditions oi the previous year in iilfested districts. Extel~sivellotcs have been made on tllc biology of several of these parasites, but they are still too il~completefor pub- cation. 'Ithe follolvi~ig species have beell bred in considerable lumbers :- ADULT CLIMATIC HYMENOPTEPA YEAR MOTHSCONDITIONS Bonneto comta 2.5% 1913 Zele Sp. 1. Specimen. ? Gonia capitata 39.0% Medium - 7 --- zele SP. 2.0% G. capitata 1914. 43.0% 5.0 % ' Drought -!vet. .dimicj7iatus 2.0% (minimum) -- I Met. dimidi:rtus 2 0 % G. capitata (min)7.5% 1915 13.0% Wet - (estimated) B. comta(min) 11.0% No record. Gonia I919 !Met. dimidiatus 10.0% ? Dry - capitata about 5.0% 1920 &at.climidiatus50.0% Records incomplete ? Dry --- - The figures given for Hymenoptera are those obtained by dissection, as are those for 'rachlnids other than in tlle years 1914 and 1915. During these years full grown larvae were placed in breeding cages in Julie and records were kept of the adult moths and parasites that emerged in the fall and following Spring. Froin the low nunlbers of cutwornis accounted for in these breeding cages,-j2S/c and 33% respectively,-it can he assumed that the actual parasitism was considerably higher than the figures i~ldicate. Other species bred in sniall numbers are:-Peletcria robusta, Wried. 1913 arld Erlzesfin radicz~~lzFab. 1916. Both are Tachinids. 'I'he habits of the more important parasites are briefly as follows:- THE: CANADIAN ENTOM~O!L~OCTlST 9 9 Meteorus diwzidiatus Cress. (Teste Rrues). Two generations per annunl. Hibernate as iarvae i11 overwintering cut- worms, such as Buxoa tristicula Morr. Adults emerge in May, ant1 parasitize P. orthogonia and other Noctuidae. 'l'he fenlale lays about twelve eggs in each host. Our records of the date of appearance of the second generation adults indicate a considerable variation from year to year, but the majority have emerg- ed in July. On account, it is thought, of the underground hahits of P. ortlzogo~ziathe percentage of infestation by this Braconid is never as high as it i's in the Euxoas, but it is of interest to note that we have bred it from Sidevzia devastator Brace, a species of cutworm that has never been recorded as coming to the surface. Gonia capitata DeGeer, and other Species. ('l'este Tothill). At least two closely allied species of 'l'achinidae, with similar habits, art included here. The oiily differences that we have been able to detect are slight variations in larval and adult structures. We have found three types of stage 1 larvae. All of the species have one generation per annuin. They hibemate as ?uparia. The adult emerges in May, and lays thousands of minute eggs on vege- tation. When eaten by cutworms these eggs hatch and the escapillg larvae ma- ture at about the time that the host pupates. They transform into the hiber- nating ~upariumeither in the soil, or in the dead larva or pupa of their host. The selection of vegetation by the fly, and the location of the eggs on selected plants, plays an important role in the value of the parasite. We have found the most abundant oviposition on the blades of Blue-joi:it (Agropyron Smithii.) though it is frequent on other native grasses, and to a slightly less extent on imported graminae, including grain crops. Native dicoty. ledons may carry a few eggs, but we have never found them on introduced plailts Leloilging to this class. Unfortunately P. orthogonia does not feed readily upon ~lue-jointand we did not find that G. capitatu selected the lower ~ortionsof the plallts for ovi- l.,osition ill preference to the upper. The high percentage oi parasitis111 is rather since P. orthogo~ziafeeds almost entirely below the groulld. Tt would appear, however, that periods cf drought are beneficial to this parasite sillce the P reduced growth of vegetatioll necessitates a more ab~uldantoviposition 011 avail- able plants. Bonneta comta Wied. (Teste Tothill). Very little is known of the life history of this species. The adult appears in !uly and August, and it belongs to the group of Tachinidae that are larvi~ar- ous. Tt is probably, therefore, double brooded, though it has not been bred fro111 overwinteriilg species of cutwoi-ms. Regarding the selection of plants for the supposed larviposition the followiilg figures, obtained in 1915, are of interest. P. orthogonia larvae co.llected from Spring LVheat were 21% parasitized P. orthogonia larvae collected from Fall Wheat were 2% parasitized. P. orthogonia larvae collected from ,Alfalfa were 0% parasitized. )1 1his suggefsts a similar habit to that of Golzia cupitata in the selectioil of plants. With a more complete lcnowledge of the habits of these parasites? particu. 100 TBE CANADIAN ENTOMlOLOGIST larly of the 'l'achinids, it may be possible to encourage their increase by the selec tion of favorable crops, and a consideration of the illost advarltageous dates o4 seeding. PSITHYRUS LABORIOSUS FABR. IN THE NESTS OF BUMBLEBEES (EIYM). BY THEODORE: H. PRISON, Urbana, Illinois. Of the nine or possibly terl species of the genus Psithyrus occurring irr America, North of Illexico, only two have ever been recorded from the nests of Ijun~hlebees. \;\'hen Franklin's work on "'I'lhe Bombidae of the New World" appearetl in 1913- there had not been recorded a single authentic instance of a Psitl~~vltshaving been taken in a bumblebee's nest in this country. The fact that tl?any -4merican writers had mentioiled the iilquiline habits of Psithyrus was entirely due to the ilLlillerous European records on the subject. Mr. F. IT:. L. Sladen in the Canadian Eiltomologist for March, 1915, wa: the first to record the finding of a species of Psithyru,p in a Brevvtus (Bombus) nest ill the lUearctic region. In this article he reports the discovery of Ysitlzyrz~~ i~zsz~lavisSm. in the nest of Brcnzzu (Bonzbz~s)flavifvo~zs Cress. on July 7, 1914 at Agassiz, British Colun~bia. In April, 1916 in the Bulletill of the Brooklyn Entomological Soc'iety, the writer recorded the presence of Psitlzyrus variirbilis Cress.