^ATi iSi BO. E-460 December 1938 United States Department of Agriculture Bureau of Entomology and Plant Quarantine TECHNIQUE AND EQUIPMENT FOR HANDLING TWO HYMENOPTEROUS PARASITES OF THE EUROPEAN CORN BORER, WITH PARTICULAR REFERENCE TO PROLONGING THEIR HIBERNATION By K. D. Arbuthnot and W. A. Baker, Division of Cereal and Forage Insect Investigations* Introduction The synchronization of liberations of a parasite with the occurrence of its host in stages suitable for attack sometimes necessitates manipula- tions of the parasite in order that it may be available for colonization at the desired time. This problem has been encountered with Microgaster tibialis Nees and Eulimneria alkae Ell. and Sacht., two hymenopterous parasites of t"he European corn borer f Pyrausta nubilal is (Hbn.)). v/hen they have been imported into the United States from Europe and the Orient (2, 4, 5, 6, 7). The equipment, constructed to handle the emergence of these species, has been found readily adaptable to other parasites. Equipment The manipulation of the parasites was accomplished in the following two phases: (1) Storage from the time of their receipt at the laboratory until the time for starting development to provide for synchronized field releases, and (2) development of the material following storage, including emergence of adults and their transfer to cages for transportation to the field location. The facilities provided for these activities and the equipment utilized are described in the following paragraphs. The emergence cage (fig. 1) is 7 by 7 by 15 inches, with wooden top, bottom, and ends, and with open sides to form the front and back of the cage. 1 These data were accumulated at the Monroe, Mich., field laboratory for European corn borer research from 1928 to 1932, as a part of the program for colonization of parasites of the European corn borer in the Lake States area. The assistance of fellow workers in this project is acknowledged as follows: G. T. Bottger, who conducted the work in 1928; Philip Luginbill and E. W. Beck for the photographs; and Arl.o M. Vance for helpful suggestions in the preparation of the manuscript. - 2 - The edges are smooth and even to facilitate close fitting of the front and back. Wooden strips (§■ by -g- inch) are fastened flat along the front and back edges of the bottom. The front and back are 7 by 15 inches. Each consists of a frame, constructed of f by f inch wooden strips, over the inside of which 40-mesh copper screen is stretched and tacked to the outside of the frame, presenting a smooth screen surface which fits tightly against the edges of the cage. (An extremely close fitting of these surfaces is necessary to prevent the escape of chalcid hyperparasites. ) The front and back are held in place by four No. 105 rubber bands, which are fastened to the corners of the back, stretched across the cage, and each one fastened to the proximal corner of the front. The migration cage (fig. 2) consists of four wooden frames of 1 by 1 inch material, over the inside of which two thicknesses of a good grade of cheesecloth are stretched and tacked to the outside of the frame. These frames are fastened together by screws, to form the back, top, and ends of the cage, the inside dimensions of which are 15 by 20 by 34 inches. This cage rests on a plain wooden table having a top dimension of 24 by 40 inches which serves as the bottom of the cage. The migration light consists of a metal reflector constructed to concentrate the light and having an 18-mesh wire screen front to prevent the entrance of parasites into the reflector. A 40-watt frosted bulb sup- plies the light. This unit is mounted on an adjustable tripod, 1 foot behind the back of the migration cage. The suction unit is adapted from a small hair drier, with all parts except the motor, handle, and fan casing removed. A brass collar,- 2 inches in diameter and 1 inch deep, is soldered to the fan casing, around the suction opening of the fan. The collecting cage is a celluloid cone, with a base 2 inches in diameter, with 80-mesh copper screen cemented to the inner edge of its base, and an apical opening j inch in diameter. A ring of celluloid, I inch wide, is cemented to the base of the cone to increase the friction surface coming in contact with the brass collar when the cone is inserted into this ring. The parasite cone is 10 inches and the hyperpar- asite cone 6 inches in length. This cage will accommodate 50 Eulimneria alkae or 100 Miorop;aster tibialis. The liberation cage is of the same construction as the migration cage (wooden frames covered, inside, with cheesecloth, and screwed together), except that one end has a removable composition wallboard cover, held in place by rubber bands which are fastened to the wooden frame and stretched over the cage end. A hole in this end, 1^ inches in diameter, is stoppered by a cork and provides the opening through which the collecting cage is inserted when parasites are transferred from the migration cage into the liberation cage. The cage is 8 by 10 by 16 inches inside dimensions and will accommodate 2,500 Eulimneria alkae or 5,000 Microgaster tibialis. A series of rooms were designed to facilitate efficiency in handling the parasites during emergence and preparation for liberation in the field. - 3 - and, at the same time, to provide maximum precautions against the escape of hyperparasites. The arrangement of the rooms and equipment in them is shown in figure 3. A basement room 11 by 13 feet (143 square feet), with cement and stone block walls, and a ceiling of composition wallboard, 6 feet high, was divided by double wallbcard partitions into three rooms of the desired dimensions. The emergence room, having 66 square feet of floor space (6 by 11 feet), is the most remote from the laboratory entrance. It has the natural earth floor left after excavating, since the native clay was found to pack firnly enough to form a satisfactory floor. Temperature and humidity are controlled by equipment previously described by the authors (1) . Racks which hold the emergence cages are built along the walls of this room. The workroom and trap room floors are of solid cement construction, since they must withstand considerable wear and also must be dried and cleaned when they have become wet or littered as a result of activities incident to parasite handling. The walls and ceiling of the workroom are painted white to facilitate detection and collection of insects which escape from the migration cage. An opening from the ceiling of this room to the out of doors, 16 inches square and covered with 80-mesh copper screen, has an adjustable trapdoor closure, which permits temperature control of the workroom by ventilation. Without the ventilating arrangement, the escape of heat from the emergence room into the workroom, through the communicating door, often raises the temperature of the workroom above 75° F. A temperature of 70° to 75° allows sufficient parasite activity for the migration of the insects but does not allow excessive activity, such as occurs v/ith higher temperatures and inter- feres with the handling of the parasites. All manual operations incident to emergence and preparation of the adult parasites for release in the field, except the wrapping of shipping containers, are conducted in this room. The trap room is for the purpose of preventing escape of insects, especially hyperparasites, from the work and emergence rooms. Its principal feature is a lighting arrangement consisting of a 40-watt frosted bulb inside a depressed wall section which is 2 feet square and 6 inches deep, covered by a single-glazed glass, set flush with the wall. The light is operated by a switch outside the door communicating with the laboratory basement. This door is located in such relation to the light that it does not receive any direct rays. When any equipment or person passes from the workroom to the laboratory proper, a thorough brushing, to dislodge any clinging insects, is administered in the trap room. Liberation cages, con- taining parasites ready for field releases, are retained in this room until they are removed from the laboratory for transportation to the field. Emergence Technique Since Microgaster tibialis and Eulimnerla alkae are collected in the cocoon ctage in Europe and the Orient during the winter months, shipped to - 4 - the United States, and reared in this country, the logical means of securing adults later than the normal time of occurrence apparently is to delay emergence. The practical application of this method has been discussed in a previously published article (2). To evaluate properly the storage methods used for cocoons, it was important to establish a suitable standard emergence method. Experience with other parasites served as a guide for this work. Three environments were used in this preliminary study, (1) outdoor cages, having wooden sides and 80-mesh hardware cloth tops and bottoms, exposed to all prevailing weather conditions, as representative of as natural conditions as possible, with a definite precaution to prevent escape of hyperparasites; (2) cages having wooden tops, bottoms, and sides, and 80-mesh hardware cloth fronts and backs, in a cellar room, cooled by circulation of outdoor air when low temperatures prevailed out of doors, and relative humidity maintained at above 85 percent, a partially controlled condition, modifying natural con- ditions; and (3) controlled incubator conditions, 80° F. and 80 .o 85 per- cent relative humidity. The results of test emergences in these environ- ments are summarized in table l. Table 1, — Emergence of Microgaster tibialis and Eulimneria alkae under three environmental conditions Environment Out of doors, exposed to natural conditions Microgaster tibialis 1930 Eulimneria alkae 1931 Period Number Percent Period Number Percent of emer- of emer- of emer- of emer- gence cocoons gence gence cocoons gence May 1 to 12 526 91.80 May 15 to 25 50 91.7 Cellar room, cooled by outdoor air, relative hu- midity above 85 percent May 11 to 24 952 92.13 May 8 to 25 Incubator, 80° F. , 80-85 percent relative humidity Feb. 28 to Mar. 15 152 88.06 Feb. 15 to 26 53 50 80.2 91.5 The results shown in table 1 indicated no great difference in the percentage of emergence secured by the various methods. Accordingly, the la-:', method (emergence under incubator conditions) was used as a basis for comparison of all storage methods studied. - 5 - A temperature of 80° F. was used for emergence, since this was being utilized generally in the laboratory for other purposes and was, therefore, practical from the standpoint of equipment and space. General observations on emergence in the years 1929 and 1930, however, showed a need for more accurate information on the effect of humidity and contact moisture. In 1931 experiments were conducted to determine practical moisture conditions on parasites in cocoons for securing the greatest numbers of healthy adult parasites. Tables 2 and 3 contain the summarized results of these experi- ments for Mlcrogaster tibialis and Eulimneria alkae, respectively. In these experiments all emerged adults were collected from the emergence cages daily, and their condition noted. Table 2. — Emergence of Microgaster tibial is at 80° F. , with varying con- ditions of relative humidity and contact moisture Percent Sprayed Number Percent Pe rcent of relative moisture of emerged adults deadi humiditv applied cocoons 35 none 350 48.79 71.07 daily 350 59.60 58.78 70 none 350 88.61 14.00 daily 350 88.88 12.41 85 none 350 87.35 13.58 daily 350 94.55 6.87 95 none 350 89.06 11.45 daily 350 89.51 14.39 1 Emerged from CQCoong but died prior to removal at daily intervals Table 3. — Emergence of Eulimneria alkae at 80° F. , with varying relative humidity and contact mojsture conditions Percent Sprayed Number Percent Observations on vitality relative moisture of emerged of adults at time of humiditv applied cocoons emergence 35 70 85 95 none daily none daily none daily none daily 152 161 159 158 150 159 164 159 83 .45 82 .40 89 .40 92, ,21 87. 68 90, ,85 86. 71 93. 46 Many weak, not able to free themselves of cocoon. A few weak individuals. Many weak individuals. A few weak. A few weak. Good condition. Good condition. Good condition. - 6 - Examination of table 2 shows the desirability of a relative humidity of 85 percent with contact moisture applied daily for securing the great- est numbers of Microgaster tibialis for liberation purposes. Table 3 does not show marked differences in rate of emergence occurring with Eulimneria alkae such as appear with M. tibialis. However, the observations of the condition of adults in the last column of this table serve as an index of the desirability of the various conditions. The higher percentage of emergence at 95 percent relative humidity with sprayed moisture applied was undesirable because of mold, which quickly developed on the cocoons and in some instances interfered with the emergence. Also, a few adults were hampered by free water, which collected on the smooth surfaces of the emergence cages and stuck them to the cage sides. When weak individuals appear at the time of emergence, mortality at the time of release in the field is greater than when all adults are strong at the time of emergence. For practical purposes a relative humidity of 85 percent with daily sprayed moisture proved the most satisfactory. Storage of Cocoons The emergence condition utilized for the determination of successful cold-storage manipulation was a temperature of 80° F. , relative humidity 85 percent, with daily application of sprayed contact moisture. In 1928 and 1929 commercial storage plants in Toledo, Ohio, were utilized. In 1930 and subsequent years a storage room at the Monroe, Mich., laboratory equipped with a commercial storage unit was used, Manipulation of Microgaster tibialis With only one exception, v;hich is mentioned later, all Microgaster tibialis cocoons received in the early February shipments contained prepupae. Each year the rates of emergence resulting after retention of prepupae in cold storage from the time of receipt until removal from storage and place- ment in emergence conditions during the latter part of June (to produce adults for colonization from July 8 to 16, which is the desired time for making liberations) have been satisfactory. The percentages of emergence obtained each year and the numbers of cocoons utilized are shown in table 4. The storage temperatures in 1928 and 1929 were maintained below 40° F., but accurate records of the conditions were not obtained. In the other years the temperature was maintained between 33° and 37° F. and the relative humidity above 90 percent. In 1932 one lot of cocoons, received in February, contained pupae and adults as well as prepupae. Some of these cocoons were placed in the incubator for emergence, without being subjected to cold storage, and the remaining ones were placed in cold storage with the other cocoons, Sam.ple lots were removed from storage, some dissected and others placed in an incubator for emergence, at intervals until the time when the cocoons con- taining only prepupae were placed in the incubator (June 25) for emergence for colonization purposes. The only change noticeable in the dissections during this period was the death o^ the adults that werp contained in the - 7 - cocoons, after approximately 2 months in storage. The emergence from cocoons placed in the incubator on different dates was as follows: February 18, 67.86 percent; March 16, 39.04 percent; May 10, 19.07 percent; and June 25, 16.54 percent. An increasing number of deformed adults appeared in the later groups. Further reference to these Microgaster tibialis adults is made in the discussion of Eulimneria alkae . Table 4. — Numbers of cocoons of Microgaster tibialis and percentages of emergence in incubators after retention in cold storage from February to June Number Year of cocoons 19281 300 1929 2 900 1930 2 12,500 19313 19,600 1932 3 14,000 Rate of emerf gence (percent) 74. ,0 89 .3 86 .2 87. 1 88 .4 1 An insectary room with no heat control; high humidity maintained by evaporation from cotton bats. 2 Controlled temperature of 80° F. and relative humidity above 70 percent. 3 Controlled temperature of 80° F. and relative humidity of 85 percent. Manipulation of Eulimneria alkae In 1929 the first attempt to delay the emergence of Eulimneria alkae by cold storage was made, and the summarized data for each of the years 1929 to 1932, inclusive, are shown in table 5. The results obtained in 1929 were very unsatisfactory, the emergence from the 230 cocoons on July 1 being only 35 percent, as compared with approximately 70 percent from 300 cocoons in April. A greater number of cocoons were placed in storage in 1930. Dissections of cocoons, made at the time they were placed in storage, showed that they contained larvae and prepupae. Groups of cocoons were removed from storage at intervals and placed in incubators (80° F. , 85 percent relative humidity) . The percentages of emergence are shown in table 5 . - 8 - Tcible 5. — Numbers of cocoons of Eulimneria alkae and percentages of emer- gence in incubators after retention in cold storage from February to the time indicated • Time when cocoons were Rate of placed in Number emergence incubators of cocoons (percent) 1929 April 300 70.0 July 230 35.0 1930 May 200 93.5 June 6,500 59.5 July 250 38.2 1931 February 125 84.0 March 150 92.5 April 150 93.9 May 150 91.3 June 225 92.1 September 225 75.5 1932 June 6,500 82.4 Dissections of the cocoons which failed to produce adults and the condition of certain adults which emerged showed an increasing number of individuals in the later groups having a type of deformity that had previous- ly been observed (3, p. 15) in Exeristes roborator (F.), an imported parasite of Pyrausta nubilalis, during laboratory rearings. This condition, in E. roborator, was caused by cold-storage temperatures applied to the para- sites while they were in stages other than a true hibernating condition and was the same type of deformity seen later in Microgaster tibialis, as heretofore mentioned. The observations made throughout 1930 indicated that E- alkae responded favorably to the cold-storage treatment applied when the stored cocoons contained only larvae which had not voided the meconium. The voiding of the meconium apparently indicated a resumption of development following hibernation. All the Eulimneria cocoons received in February 1931 contained larvae, none of which had voided the meconium. These cocoons were placed in cold storage at a constant temperature of 35° F. and relative humidity of from 90 to 100 percent. They were removed from storage, and emergence was secured under the standard emergence conditions. Dissections of cocoons throughout the storage period showed that no larvae had voided the meconium, except in the last group, which was dissected on September 9. In this group 8.3 per- cent of the larvae had voided the meconium. Adults emerging from cocoons which were, removed from storage during the last part of June were available - 9 - for colonization during the second week of July, which was the time desired for making liberations in 1931. All the cocoons received in 1932, contain- ing suitable larvae, were handled by this method, and an emergence of 82.4 percent was obtained for colonization. Prolonged Retention of Adults Very few of the cocoons of Microgi;aster tibialis received at the laboratory have contained stages other than prepupae, and no effort has been made to find a method by which this species could be handled when received in other stages. However, each year a considerable portion of the Eulimneria alkae cocoons received have contained stages other than larvae which have not voided the meconium. Since these stages do not respond favor- ably to the cold storage treatment previously discussed, tests of some pos- sible means of retaining adults after emergence fro.m their cocoons were attempted in 1931 . Experience with various other species of parasites, in confinement, had led to the generalization that an insect which does not hibernate in the adult stage will have the greatest longevity in conditions that prevent flight but permit enough activity to allow free feeding. Accordingly, the nearest available approach to these conditions was used as a starting point. A basement storage room was selected for the experiments. For practical purposes, arbitrary limits of mortality, from a minimum of 25 percent to a maximum of 75 percent, were selected as a test of efficiency, the former being considered "good" and the latter as too high. Adults which had emerged after storage from cocoons at 80° F. and 85 percent relative humidity were used in this experiment. Sugar solution and water on absorbent cotton were available to the insects at all times. Table 6 contains the summarized results obtained. Table 6. — Longevity of adults of Eulimneria alkae in confinement, under various conditions of temperature, at relative humidities above 85 percent, and with sugar and water available for feeding* Date Date on Days from Mean tem- Date on Days from Mean tem- of which the emergence perature which the emergence perature from emer- accumulated to 25% from accumulated to 75% emergence gence mortality mortality emergence mortality mo rtality to 75% was 25% to 25% mortality 39.5° F. was 75% Apr. 12 mortality Feb. 22 Mar. 21 27 49 41.5 Mar. 7 Apr. 1 25 40.0° F. Apr. 14 39 42.0 Mar. 19 Apr. 10 22 42.5° F. Apr. 21 33 45.0 Mar. 31 Apr. 23 24 47.0° F. Apr. 28 29 47.5 Apr. 14 May 3 19 48.5° F. May 7 23 49.5 Apr. 28 May 15 17 50.1° F. May 19 21 51.5 May 25 June 18 23 58.5° F. June 23 28 59.0 I Seventy-five males and seventy-five females were used in each date group. ATE Pl-^NT BOARD QT/ -10- Various other groups of adults were supplied with conditions ranging from low temperature, which induced complete inactivity, to temperatures in which flight was frequent. Water, sugar solution and water, granulated sugar and water, and honey and water were used as foods. Under each of the conditions utilized the rates of mortality were similar to those shown in table 6, Cocoons containing stages unsuitable for subjection to cold storage are known to produce adults in numbers from approximately April 1 to May 15. If these adults were retained under the above conditions, few, if any, would be alive at the time desired for making liberation (July 8 to 13). Dissections of individuals, during the time they were retained in the above conditions, showed a rapid decrease in their fatty tissues after 7 to 10 days, with a corresponding lack of vigor as evidenced by decreased activity. These data indicate that parasites received at the laboratory in stages not suitable for retention in cold storage are of little, if any, value for colonization, Outline of Standard Procedure By utilizing the information procured from the observations presented in previous sections of this circular, a standard procedure has been es- tablished for handling cocoons of hymenopterous parasites of the European corn borer which have been imported for release in infested areas of the United States, in order to insure their release in the field during the optimum period. The procedure is briefly outlined in the following para- graphs. Cocoons of Eulimneria alkae containing larvae which have not voided the meconium and those of Microgaster tibialis containing prepupae can be successfully subjected to cold storage for the necessary prolongation of the hibernation period. The condition of the parasites in their cocoons is determined by dissection of a sample from each group of cocoons when they arrive at the laboratory. If at that time the cocoons have a temperature near that which is to be utilized for storage purposes, care is exercised to maintain it during such handling as is necessary before they are placed in storage. High temperature of cocoons upon receipt (45° F. or above) is rectified by gradual reduction to the storage temperature, rapid changes in temperature being avoided. A high relative humidity is maintained in the packages of cocoons. This is usually insured by introducing moisture on wet cloth wrappings. Lots of cocoons collected from different localities, or at different dates, are kept separately, since different groups of cocoons sometimes show considerable differences in the numbers of contained hyperparasites, in vitality, etc. Thus, if differences do appear, the data are not con- fused by mixed groups. When the individual lots are large (500 cocoons or more), a small group (25 to 50 cocoons) from each lot is placed in the emergence environ- -11- ment, and emergence is secured sipproximately 1 month before the d.ate of emergence for colonization purposes. This serves as an index of the num- bers of adult parasites which will be available for colonization by showing the contained percentage of hyperparasites, presence of other species which cannot be detected except in the adult stage, sex ratio, and rate of emer- gence. Cocoons suitable for storage are placed in containers which allow them some air space. Nonrusting metal cans (3 by 5 inches) with screened openings for ventilation have been used successfully for this purpose. These cans containing the cocoons are placed in storage at a temperature of 35° F. and relative humidity of 90 percent. When cocoons are removed from storage for emergence, they are ex- posed to a rise of 8° (from 35° to 43° F. ) during the first 6 hours and a rise of 35° (from 45° to 80° F. ) during the next 12 hours. (This is the tem.perature inside of the package, determined by inserting a thermometer among the cocoons, with its upper end (scale) projecting from the package.) High humidity is maintained by wrapping the cans, containing cocoons, with wet cheesecloth covered by an outer wrapping of three layers of heavy wrapping paper, before the cocoons are removed from the storage chamber. The usual means of accomplishing the temperature change just mentioned has been to place the wrapped package of cocoons in a mechanical refriger- ator, operating at a temperature of 42° F. . and allowing the cocoons to attain this temperature. Refrigeration is then shut off and the chamber allowed to warm gradually, the temperature rising as indicated. If this rise in temperature proceeds too rapidly, refrigeration is restored for short periods to retard the rate of temperature increase. When the temper- ature has risen to the highest point that can be attained in the refrigera- tor (depending on surrounding conditions), usually 70° to 75° F. , the pack- ages are placed in the emergence room at 80° F. until the temperature of the cocoons has risen to at least 75° F. 7/hen the cocoons have reached this temperature, the packages are unwrapped and the cocoons are scattered in a single layer on the bottom of the emergence cages. These cages are placed in the c:iergence room, where a temperature of 80° F. and relative hum.idity of 85 percent are maintained. Contact moisture is applied daily as a fine stream from a special nozzle through the cage front. The amount applied is that which leaves no free moisture on cage wal.ls or bottom, but which gives each cocoon a small amount of sprayed water. During emergence all adults are removed from the cages once each day by the follov/ing method: The emergence cages are removed singly to the work- room and water is sprayed into the back of the migration cage and libera- tion cage until the cheesecloth is well dampened and serves to hold granu- lated sugar when it is sprinkled over these surfaces. A light is placed 1 foot behind the back of the migrat.ion cage and all other lights are extinguished. Migration is accomplished by placing the emergence cage just inside the open front of the migration cage, opening it, and allowing the adults to proceed toward the light to the back of the migration cage. Those adults which fail to respond to the light's influence are disturbed -12- with a camel 's-hair brush to induce activity. When all the parasites have left it, the emergence cage is closed and returned to the emergence room. All hyperparasites are collected in the special collecting cage and killed immediately in a cyanide jar. Primary parasites are collected in the collecting cage by placing its open end close to each parasite, which is then disturbed with a camel 's-hair brush to dislodge it from the cheese- cloth, the air current from the suction unit drawing it into the cage. Fifty Eulimneria alkae or 100 Microgaster tibialis is the maximum capacity of the collecting cage. The suction is then stopped and simultaneously a hand is placed over the open end of the collecting cage to prevent escape of parasites. The collecting cage is examined carefully for possible hyper- parasites or other species of parasites which may have entered. The stopper of the liberation cage is removed, the open end of the collecting cage inserted, and its side tapped to dislodge the contained parasites, thus causing them to fall into the liberation cage. The collecting cage is then removed and the stopper replaced in the liberation cage. All colonies remain in the liberation cage for at least 24 hours, at temperatures from 70° to 80° F,, to permit them to feed before being re- leased in the field. Literature Cited (1) Baker, W. A., and Arbuthnot, K. D. 1931. An incubator room. Jour. Econ. Ent. 24: 444-449, illus. (2) and Arbuthnot, K. D. 1933. The application of artificially prolonged hibernation of parasites to liberation technique. Ann. Ent, Soc. Amer. 26: 297-302. (3) and Jones, L. G. 1934. Studies of Exeristes roborator (Fab.), a parasite of the European corn borer, in the Lake Erie area. U. S. Dept. Agr. Tech. Bull. 460, 25 pp., illus. (4) Jones, D. W. 1929. Imported parasites of the European corn borer in America. U. S. Dept. Agr. Tech. Bull. 98, 27pp., illus. (5) Thompson, W. R., and Parker, H. L. 1928. The European corn borer and its controlling factors in Europe. U. S. Dept. Agr. Tech. Bull. 59, 62 pp. , illus. (6) and Parker, H. L. 1930. The morphology and biology of Eulim- neria crassifemur, an important parasite of the European corn borer. Jour. Agr. Research 40: 321-345, illus. (7) Vance, A. M. 1932. Microgaster tibialis Nees as a hymenopterous parasite of Pyrausta nubilalis H.ibn. in Europe. Ann. Ent. Soc. Amer. 25: 121-135, illus. t I Figtire 1, — Emergence cage with front open to show cocoons of Eullmnerla alkae. Figure 2* — View of workroom showing eqtiipraent in usej (a) ceiling ventilator with operating cord, (b) migration cage, (c) migration li^t, (d) emergence cage with front open, (e) cyanide Jar for killing fayperparaeites, (f) collecting cage attached to roctlon vmit, (g) work table, and (h) liberation cage. m TRAP FJOpM 6-0 X 6-6 WORJSROOM 5-0>G-6" T RACK FOR EMERGENCE CAGES la. HUMIDIFIER EMERGENCE ROOM ©Vxn-o* HEATING UNIT RACK FOR EMERGENCE CAGES A. i^ l> l> i> l> f> l> i> ^-^ Figure 3, — Plan of rooms and the contained equipment, UNIVERSITY OF FLORIDA 3 1262 09224 6650