H. Pinkus.
The Life History and Habits of Spalangia muscidarum Richardson, a Parasite of the Stable Fly.
Psyche 20:148-157, 1913.

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148 Psyche [October
his first specimens on March 23, and on the 30th observed many visits to the flowers of Salii. On March 31 a female was seen looking out from the mouth of nearly every burrow, probably waiting for a warmer temperature, for on April 6, when there was a severe snow squall, no bees were seen flying about the burrows; and a few which had ventured to fly to the willows were numbed by the cold.
Swenk states that he examined a female from Durham, N. H., taken Oct. 5, 1899, and has also seen a few other autumnal speci- mens of C. incequalis. He regards them as individuals appearing prematurely, which normally would not have come out until the following spring1
Colletes compactus flies in New England from about the first of September to the middle of October. I most commonly find it on the inflorescence of the goldenrod, but have one specimen taken on the flowers of Aster puniceus.
THE LIFE HISTORY AND HABITS OF SPALANGIA MUSCIDARUM RICHARDSON, A PARASITE OF THE STABLE FLYS2
BY HARRY PINK US.^
Bureau of Entomology, United States Department of Agriculture. During the summer of 1912, while assisting in the study of the life history of the stable fly (Stomoxys calcitrans Linn.), at least two species of parasites were found breeding in large numbers in the puparia of this fly. These parasites belong to the family Pter- omalidse. One has been determined by Mr. C, H. Richardson as Spalangia muscidarum Richardson; the others have not been definitely identified. S. muscidarum was found most abundant while the other species appeared in smaller numbers. They ap- pear to have similar breeding habits, although little has been done on the undetermined species.
During the investigation of the stable fly a lot of oat straw, placed in a pan and kept moist, was placed in the laboratory yard '("~;ecific Characte-s in the Bee Genus Colleies," Contributions from the Dept. of Ent., Univ. Neb, No. 1, p. 32.)
2 Published by permission of the Chief of the Bureau of Entomology. Deceased August 27, 1913, at Dallas, Texas.



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19131 Pinkua-History and Bat-its of Spdangia Mvscidurum 149 near the stable. When the straw began to decay stable fie% visited it in large numbers, depositing thousands of eggs. In ad-
dition to the stable fly, a number of other species were found to be breeding in this rotting straw, such as Phorid~e, Chironomidse and Anthomyidie. No house flies (Musca domestics. Lim.) or any other species of flies which commonly, breed in dung were found although Musca hesiica was present in the vicinity in consider- able numbers. In a few weeks great numbers of Stomoxys larvae of various sizes, as well as pup, were found in the straw. At this time a screened cage was placed over the pan in order to collect the flies as they emerged. Numbers of flies appeared daily for some time but the number was observed to diminish noticeably later. Upon examination of the straw the majority of the Sto- moxyspupae were found rather dark in color, some being almost black. "When the cephalic ends of these pup= were broken off in some eases the pup* of parasites were found to be contained within, and in others the adult parasites came out as soon as; the pup= were broken. Considerable numbers of the Stornoxya pup= were dead but no parasites were found within them. These pup= were in the form of a soft, whitish, malodorous mass. The death of these pupae appeared to be due, in part at least, to the par- asites, as will be explained later,
Spdangits, mu~cidarum Richardson appears to have a wide distribution. It has been bred from the house fly by Mr. C. H. Richardson, Jr., near Boston, Mass., as well as by Doctor L. 0. Howad at Washington, D. C., from the same host. During this investigation, adults emerged on October 7,1912, from Stomoxys pupae collected by Mr. F, C. Bishopp at Gainepville, Texas on September 6, 1912. Other adults began emerging on October 36, 1919, from puparia colleited by F. C. Bishopp and E. 0. G. Kelly at Wellington, Kansas, on September 21, 1912, and others appeared on January 15, 1913 from puparia collected October 85, 1912 by F. C. Bishopp at Addis, Louisiana, Numbers have also been bred from pup collected at Denison, Texas, December 6, 1912. As has been pointed out, the parasite is undoubtedly very common in the vicinity of Dallas, Texas. At Dallas the breeding was conducted both in the laboratory and out of doors. In the latter situation some adults emerged at



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150 Psyche [October
different times during the winter.
These adults were killed when
a temperature of 28' was reached on January 2,1913. The imma-
ture stages, however, remained in perfect condition throughout the cold weather, and undoubtedly large numbers will emerge in the spring. In the laboratory, emergence continued through- out the winter. The greatest number appeared from pupae kept in glass tubes in a well heated room. In another room, in which the temperature ranged somewhat lower, emergence was less rapid. At temperatures from 55 to 60' F. the adults became inactive. Breeding progresses well at 70' and somewhat higher temperatures increase all activities.
Adults kept at 110' (in the dry atmosphere of an incubator) died very quickly.
The adult parasites are scavengers in habit. In cages no pre- pared food is necessary for them. They prefer to feed on the re- mains of the host, and very often crawl back into the puparium and stay there for some time. While within the puparium they have been observed to feed upon the remains of the dipterous pupae although honey and water were at hand. In no case did the adults pay much attention to artificial foods. They are seldom found anywhere except in and around the breeding places of their hosts. In flight the body is held in a vertical position with head up and wings extended horizontally. When disturbed, both sexes have the habit of "possuming." The legs are drawn together and the insect drops for a few seconds and then quickly resumes activity in order to escape. It appears that the parasites remain in one place as long as they have plenty of fly pupae to parasitize. Probably dispersion takes place when the parasites become nu- merous and they do not have a sufficient number of hosts. It has been found that each female requires a considerable number of pupae in which to deposit her eggs.
After the adults emerge from their pupal skins they have the habit of remaining within the puparia of the host for some time. During this period they gnaw more or less regular, circular holes through the puparia, but in many cases do not issue for some time after the emergence holes have been made.



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19131 Pinkus~History and Habits of Spalangia Muscidarum 15 1 Copulation takes place very shortly after emergence. The males
are ever ready for mating. They seize the females and cling to their backs, caressing them with their antennae for some time until the female exposes the ovipositor and copulation takes place.. This act has been observed to take place a number of times at short intervals. Often two or three males endeavor to secure the atten- tions of the female at the same time.
Spalangia muscidarum is a simple parasite1 and does not usually deposit a second time in a single host. When a female finds a pupa she first makes a thorough examination with the antennae and then fixes herself firmly on the pupa. She then begins to feel about on the pupa with the tip of the ovipositor, sometimes changing her position if the first spot attacked is too hard for penetration. The
ovipositor is usually inserted near the cephalic end of the puparium, generally on a suture. While ovipositing, the female is not easily disturbed. In some cases the puparium may roll over and yet the parasite retains her position. The accompanying figure (Plate I fig. 1.) of the female in act of depositing was drawn from a photograph taken by Mr. H. P. Wood. About ten or fifteen minutes are required for the deposition of an egg. Repeated efforts to induce the female to deposit an egg in a puparium which had already been deposited in were unsuccessful. In every case the female quickly recognized the fact that the pu- parium had already been attacked, and left it in search of other hosts.
A female which was supplied with fresh pupae as fast as oviposition took place was observed to deposit in fifteen different pupae in succession. She would have, undoubtedly, deposited in many more pupae had they been supplied, as she appeared strong and active after having laid these eggs. Subsequent examination of these fifteen puparia showed that immature parasites were developing in four and all of the others were dead, probably as the result of the insertion of the ovipositor. When numbers of puparia were supplied to parasites in cages, in only one case did an adult -
fly emerge, the others having succumbed to the attack of the parasites.
1 Pierce: On some phases of parasitism displayed by insect enemies of weevils. Journ. Econ.
Ent., vol. 3, p. 452, 1910.




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152 Psyche [October
The female will readily oviposit in many species of dipterous pupae. Evidently it has no preference. In addition to Stomoxys calcitrans the following species have been parasitized experimen- tally: Musca domestica Linn., Hoematobia serrata Desv., Helicobia quadrisetom Coq. and Pseudopyrellia cornicina Fabr. In one test a number of puparia of different species of flies were mixed with those of Stomoxys calcitrans and all were put under a glass bell jar in the laboratory. A number of parasites were introduced and observations made in order to ascertain if any preference was shown. In this case, as well as when different pup= were placed in small tubes with parasites, no discrimination between the dif- ferent species was apparent.
In nature the stable fly is undoubtedly the principal host of the parasite. This is evidently due to the breeding habits of this fly. As has been stated, the stable fly breeds largely in rotting straw or manure which contains much straw. The loose texture of this material allows the parasites to gain access to the puparia with ease. On the other hand, the breeding habits of the species which have been found experimentally to act as hosts of this par- asite, are quite different . For example, Musca domestica, Hcema- tobia serrata and Helicobia quadrisetosa breed mainly in dung or other matter which is of compact texture. By the time the larvse are ready to pupate the material in which they are breeding becomes quite compact. This prevents, to a great extent, the adult parasites from entering the substance in order to reach the host, except when the mass of breeding material is accidentally scat- tered or if some straggling specimens happen to pupate so as to be partially exposed. In nature this condition is not the rule, hence we find the parasite attacking most commonly those species which are readily reached.
The length of the developmental period of the parasite varies greatly, according to the temperature experienced. An egg (see Plate I fig. 2) which was probably of this species has been re- moved from the body of a fly pupa. A number of observations have been made to determine various points in the developmental period of the parasite.




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PSYCHE, 1913.
VOL. XX, PLATS I-
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Fig. 1.
Spalangia muscidarum Richardson.
Adult female ovipositing in puparium of Stomoxys cal- citrons Linn. F'ig. 2. Egg of Spalangia muscidarum. Fig. 3. Larva of Spalan~ia muscidarurn. Fig. 4. Pupa of Spalangia muscidarum.




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19131 Pinku *History and Habits of Splangia Muscidarum 15 3, In one series, eggs were deposited on November 7, 1912 within the puparia of Stomoxys calcitrans.
On November 12 one fly pupa
was observed to have a minute larva feeding on its eye. On De- cember 9 full-grown parasite larvae (see Plate I, fig. 3) were found feeding on the exterior of fly pupae within the puparia. One para- site pupa (see Plate I fig. 4) was also found on this date. January 30, 1913, one adult parasite emerged, thus having a total devel- opmental period of 84 days. During this period the average mean temperature was 56.58' I?.
A number of puparia of Musca domestica were exposed to Spalangia adults November 3,1912. On November 9 the parasites were observed to be ovipositing. In at least two of these the par- asites were observed to have pupated when examined December 6. When again examined, on January 9, 1913, the pupae were becoming black. Three adults had issued on or before February 20, 1913. In this test the total developmental period was less than 109 days. In another experiment, in which Musca domestica was used as a host, parasites were placed with the pup= on Novem- ber 12, 1912. Oviposition occurred at noon on this date. Full grown parasite larvae were found on January 5, 1913, and on January 30, some had begun to pupate, thus having occupied 79 days in developing to the pupal stage at about the same tempera- ture which prevailed in the above experiment where Stomoxys pupas were used. One female parasite issued February 26, 1913, after a total developmental period of 106 days. Parasites developed from the egg to the adult in 100 days in puparia of Hcematobia serrata. In this test deposition took place on November 12, 1912. Pupation began January 30, 1913 and the first adult emerged February 20, 1913. This experiment was also conducted in the same room as the preceding experiments. In another room in the laboratory, where the temperature was considerably higher, a number of puparia of various species were exposed to parasites on November 30, 1912. Pupation had begun January 30,1913, or 61 days after eggs were deposited. This shows that the period from deposition to pupation was shortened 18 days by the higher temperature in which the developing parasites were kept. One adult female and one male emerged February 26, 1913 from a Hoematobia serrata puparium. The total develop- mental period is therefore about 88 days.



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154 Psyche [October
Examinations of puparia kept out of doors during the winter of 1912-13 showed that a few adults emerged during warm weather but the majority of the immature stages appeared to continue developing very slowly and will probably not emerge until the advent of spring.
As has been shown, the habits of the female parasites enable them to destroy a great number of fly pupa. Many of these pupae are destroyed by the development of the young parasites and others died, apparently from injury caused by the insertion of the ovi- positor. Circumstantial evidence also indicates that many fly pupae are pierced by the ovipositor to cause juice to exude from the punctures for food for the parasites. This view is strengthened by the finding in nature of numerous Stomoxys puparia, the con- tents of which have completely dried up. It would seem that if an adequate number of these parasites are present early in the season they would be quite effective in the con- trol of the stable fly. However, under natural conditions it is reasonable to assume that in general there is seldom a sufficiently great number of parasites present to cope with Stomoxys, despite the fact that the fly generally occurs in small numbers early in the spring. The development of the stable fly is considerably slower than that of the house fly and as a consequence it seldom becomes sufficiently abundant to be very injurious until in the fall. The development of the parasites is slower than that of the stable fly, hence under natural conditions the parasites are unable to control it. However, late in the fall the parasite also becomes very abundant as breeding is facilitated by the great abundance of its hosts and the high temperature which prevails at that season, With the advent of cold weather the breeding of both the parasite and host is checked to a great extent and when fatal temperatures are reached nearly all of the adult parasites are killed without having had an opportunity to deposit in the fly puparia which are still present in rotting straw and other places. This condition allows many stable flies to continue to develop through the winter and appear as adults the following spring. Those which were in



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19131 Pinkus-History ani Habits of Spalangia Musdiarum 155 the larval stage at the time the adult parasites were destroyed would be entirely exempt from attack as well as some of the pup= which had not been reached up to that time. Of course the parasites which are in the immature stages would be protected by the same conditions which protect the host and they would pass the winter successfully and emerge along with the flies in the spring. However, their numbers would be much smaller than the stable fly at that time.
By artificial means it is possible to propagate these parasites in large numbers throughout the winter and liberate them early in the spring. By this procedure it might be possible to cut down to a great extent the first generation of flies and the continued development of the parasites during the spring and summer would tend to control the flies throughout the year. In addition to the destruction of the stable fly, house flies and other injuriousspecies would also be attacked whenever the parasites are able to reach them.
Since Spalangia does not discriminate between various species of fly puparia the work 'of artificial propagation is greatly facili- tated, The writer has found it best to collect the larvae together with the manure or other substances in which they are breeding and after pupation has taken place to separate the pupae and supply the parasites with them.
The writer has modeled a parasite breeding cage (Fig. 1) which he finds quite practical for the breeding of these parasites. In the construction of this cage an empty honey box (the con- tainer of comb honey) size 8 x 14 x 9% inches in height is used. Glass is closely fitted in the front and top and a hole four inches in diameter is cut in either end. Around the inside edge of each of these holes is tacked one end of a cuff of soft muslin cloth. These cuffs should be about nine inches in length, the outer end being gathered with an elastic so as to closely fit around the wrist of the operator when the hands are inserted into the box. When not in use the cuffs are closely tied with a string to prevent the escape of parasites. At the center of the bottom of the cage a hole one inch in diameter should be cut. The entire bottom of the cage, with the exception of the circular hole, is then covered with oil cloth to protect the wood from the moisture. On top of the oil cloth a



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156 Psyche [October
layer of white blotting paper is placed, completely covexing the bottom of the cage. A narrow strip of this paper should be sewed to the large blotter in such a position as to extend through the hole- in the bottom of the cage into a vkel beneath which contab Fig. 1. Pararite breeding box (original). water. The strip of blotter takes up the water from the container and keeps the large blotter which lies in the bottom of the cage moist at all times. Four legs of a convenient height are attached to the corners of the cage and placed in cups to keep away ants and mites. These legs were 3$ inches long in the cage used in this work. A small amount of damp straw is then placed in the cage- on the blotter,
When the cage is in readiness the parasites, either in the adult or pupal stage, are introduced. If adult parasites are put into the cage the pup from which they emerged should always accom- pany them in order to furnish protection and food. Unparasitized



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