Clancy, D.W.

Marucci, P.E.

Proceedings of the Hawaiian Entomological Society

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Vol. XIV, No. 3, March, 1952 525The Biology and Laboratory Culture of Thyreocephalus albertisi(Fauvel) in HawaiiBy P. E. MARUCCI and D. W. CLANCY1BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE, AGRICULTURAL RESEARCHADMINISTRATION, U. S. DEPARTMENT OF AGRICULTUREIn 1947 the Territorial Board of Agriculture and Forestry of Hawaiisent Q. C. Chock to Luzon, in the northern Philippines, to search fornatural enemies of the oriental fruit fly, Dacus dorsalis Hendel, a seriouspest which had recently appeared in Hawaii. Numerous adults and larvaeof Thyreocephalus albertisi (Fauvel) 2, a common staphylinid predator offruit fly larvae in rotting fruits in Luzon, were shipped to Honolulu.Efforts to propagate the predator by the Territorial Board of Agricultureand Forestry were successful and widespread releases were made in Hawaiiduring the next three years.T. albertisi is known to occur in Australia, New Guinea, the Aru Islands,Ternate, in the Moluccas, and the Celebes. Nothing concerning its lifehistory and habits has ever been published.The work reported on in this paper was the outgrowth of a need foreven greater numbers of the predator for field release, and for orientationin methods of handling staphylinids in anticipation of additional shipments from parasite and predator explorers. The studies were made inthe quarantine laboratory of the Pineapple Research Institute in Honolulu.ADULT STAGEThe adult beetles are striking in appearance, having coal-black, iridescent bodies and gold elytra. The males can be distinguished by theirbroader heads, which average 2.74 mm. in width, as compared with 2.19mm. for the females, and by their slightly shorter bodies—about 11.6 mm.long, as compared with 12.4 mm. for the females.The adults are active, strongly negatively phototropic, and they donot fly readily. They emit a repugnant musty odor when handled ordisturbed. As shown in table 1, they were rather long-lived in the laboratory when kept in moist soil with an abundance of fruit-fly-infested fruits.The females lived longer than the males, their adult period averaging157 days, as compared with 109 days for the males. Mating has not beenobserved, but a single male can apparently mate with several females,since the number of fertile eggs laid in breeding jars was not influencedby the male ratio. This species apparently is not parthenogenetic, sinceunmated females isolated in separate jars laid only a few undersized infertile eggs.1 Ably assisted by Satoru Shimono.2 Determined by R. E. Blackwelder, of the U. S. National Museum, Washington, D. C.526 Proceedings, Hawaiian Entomological SocietyFigure 1.—Egg and second-instar larval characters of Thyreocephalus albertisi (Fauvel).1. Egg, 2. Urogomphi region. 3. Antenna. 4. Nasale of second-instar larva.(Drawn by J. R. Holloway)Throughout the laboratory rearings there was a very favorable femaleratio, which averaged about 2.3 to each male. No apparent seasonal variations in the s£x ratio have been observed under laboratory conditions.The adult females of T. albertisi have a rather long and variable pre-oviposition period, which ranges from 11 to 30 days with an average ofabout 19 days (table 1). The eggs were laid singly, usually under the fruit.Although the adults constructed terrestrial channels 6 inches deep, mostof the eggs were laid at or near the soil surface. In a series of weeklycounts 154 eggs were found in the first inch of soil, 46 in the second inch,and none below 2 inches.The abundance of prey seemed to have a direct effect on the numberof eggs laid, the greatest number being deposited when food was plentiful.Table 1. The longevity, preoviposition period, and egg production of Thyreocephalus albertisi*Breedingjar No. $AdultpopulationLongevity of adults (days) Egg productionFemales MalesIndividual records Ave. Individual records Preovipositionid (d)Ave. per od days) TotalAverage Week ofper maximumfemale production£fCOoOi10101113Average281479, 169, 176,197, 225, 223,250, 30761, 125, 149,156, 177(2), 184,198(2), 25325, 116, 172,239, 179, 232,246(2), 260(2)31, 55, 104(3),132(2), 139(2),187, 19516, 79, 107(2),114(2), 135,142(2), 149(2),156, 16315720316819811912136, 94, 128,169, 21861, 77, 111,184, 253239, 25321, 35(2), 55,70, 111, 153(2)16, 30(2), 44(2),51, 107(2), 114,121, 128, 149(3)109129137246798930231418111942523785165094062053248559725919th16th24th8th3rd* The variations shown in this table were partially the result of seasonal temperature fluctuations in the insectary.IO528 Proceedings, Hawaiian Entomological SocietyThe presence of fruit also seemed to stimulate oviposition. A total of388 eggs were deposited in one week by 131 gravid females supplied withheavily infested fruits, but they laid only 18 eggs the following weekwhen provided with fruit fly larvae only. When infested fruits were againadded during the third week, oviposition increased to 237 eggs.A test was made to determine how long the gravid females can retaineggs in the absence of fruit, and to estimate more precisely the importanceof the presence of fruit in egg production. Twelve gravid females of equalages, which had just begun to lay eggs, were divided into two equal lots.One group was supplied with large numbers of fruit fly larvae withoutfruit, while the other received infested guavas containing an equal number of larvae. In the first week the predators caged with both guavas andoriental fruit fly larvae deposited 40 eggs. Those in the cage withoutguavas laid only 18 eggs. In the second week, however, the staphylinidsin the cage with fruit laid only 24 eggs, as compared with 40 eggs produced by the staphylinids in the cage without fruit. The number of eggslaid during the third and fourth weeks was 29 and 9 for the beetles inthe cage containing fruit, and 32 and 7 for the females without fruit.These results indicated that gravid females are able to retain their eggsfor no more than a week in the absence of favorable conditions. Duringthe 4-week period, the staphylinids supplied with fruit deposited a totalof 102 eggs, while the beetles in the other group laid 97 eggs.The fecundity of T. albertisi is rather low. As shown in table 1, theminimum number of eggs per female was 24, the maximum 85, and theaverage 59. The adults generally required a long time to reach maximumoviposition rates, but they continued to deposit fertile eggs until death.In most of the breeding jars maximum oviposition did not occur untilafter the fifteenth week. Several females produced fertile eggs after theywere 7 to 10 months old.IMMATURE STAGESThe records on the periods required for the various developmentalstages are summarized in table 2.Egg Stage: The egg (fig. 1,1) is milky white in color, with a thin, faintlysculptured and relatively opaque chorion. la shape and appearance itresembles a very large ant egg and measures 2.26 mm. in length and 1.29mm. in width. Infertile eggs, of which there are usually very few, areconsiderably smaller and have a yellowish tinge. About 80 per cent of theeggs hatched when kept in moist soil.Larval Stage: The hatching first-instar larva cuts a neat slit throughthe chorion, which it never consumes, and almost immediately begins anamazingly active and vicious life. One newly hatched larva was observedto kill four small melon fly larvae within 4 minutes. These young predators are able to subdue fruit fly larvae of any size, and will attack pupariawhen active larvae are not available. They are also cannibalistic, eatingeggs, pupae, and even active larvae of their own kind. They are generallyfound within the first inch of soil, and often within infested fruits on theVol. XIV, No. 3, March, 1952 529soil surface. The campodeiform newly hatched larvae average 6.67 mm.in length, the head being about 1.18 mm. wide by 1.40 mm. long.Newly moulted second-instar larvae are about 13.33 mm. long. Thehead is about 1.56 mm. wide and 1.75 mm. long. Except for their largersize, they bear a general resemblance to those of the first instar. T. albertisiappears to have only two larval instars.Table 2. Duration of egg, larval, and pupal stages of Thyreocephalus albertisi.Length of Stage (days)Stage Number Lange4- 64- 88-248-18Average561311Number551312Egg 15First-instar larva 148Second-instar larva 154Pupa 127The morphological characters generally used in the identification oflarval Staphylinidae (Mank 1923), namely, the nasale or "upper lip,"the pygopod and urogomphi, and the antennae, are illustrated in figure 1.During the first half of their existence, second-instar larvae are asactive as those of the first instar, but they later become sluggish as theirbodies increase in size. They are generally found deeper in the soil andare less often seen in fruits. The full-grown larva has a greatly distendedabdomen about 17 mm. long, and in this stage it constructs a cell where itmay remain as long as 10 days, apparently without feeding, until itfinally pupates. The quiescent prepupal stage is very easily injured, andoften a slight disturbance of the earthen cell or of the larva itself mayresult in an aborted pupa or death.Pupal Stage: The pupa ranges in color from light yellow to almostbrick red, and measures about 3.65 mm. in width and 8.25 mm. in length.The head and thorax are fused, but the abdomen is capable of vigorousside-to-side and circular motion. Should the cell wall collapse, the pupacan restore its shape with abdominal movements. The pupal cell alsoprovides ample aeration, which probably prevents the growth of harmfulmolds often associated with pupae in imperfect cells. The emerging adultdoes not consume the pupal case. Its first activity is that of constructingterrestrial channels.FEEDING POTENTIAL OF THE PREDATORA series of laboratory feeding tests were conducted with both larvaeand adults of T. albertisi, to determine their potential capacities as fruitfly predators. Individual first and second-instar larvae and adults wereplaced in pint jars half-filled with soil and supplied at weekly intervalswith papaya sections containing known numbers of half-grown orientalfruit fly larvae. Similar units were held without the staphylinidjs, to serveas checks. Predation was then estimated by comparing the surviving fruitfly populations in the different series of jars. The indicated destructionof prey by each stage of T. albertisi is shown in tables 3 and 4.530 Proceedings, Hawaiian Entomological SocietyAs noted in table 3, about 11 fruit fly larvae were apparently killedper predator in 6 days by first-instar T. albertisi, as compared with 15 in12 days per second-instar predator. An average of approximately 26 fruitfly lavae were thus destroyed by each larva of T. albertisi.With regard to adult predation (table 4), each mature gravid femaledestroyed about 28 Dacus dorsalis larvae per week, as compared with only10 per week by mature males of the same age. Young females consumedfewer larvae than did older ones, and predation was greatest at the peakof oviposition. An average female may therefore theoretically consumeor destroy from 500 to 600 oriental fruit fly larvae during her entirelarval and adult life span.In separate tests both larvae and adults of T. albertisi were successfullyreared on oriental fruit fly larvae and puparia in the absence of fruit,indicating that this species is very largely or entirely carnivorous.Table 3. Destruction of third-iristar oriental fruit fly larvae by first- and second-instarlarvae of Thyreocephalus albertisi.First-instar larvae Second-instar larvaeJar No.12345678910TotalAveragePeriod(days)5855567677616Fruit flydestroyed915910613131015810811Period(days)16132016138787711512Fruit flydestroyed219 -221417131414131315015Total302431242326272428'2125826Table 4. Destruction of third-instar oriental fruit fly larvae by adultThyreocephalus albertisi.Predator adults • Larvae destroyedSex and age (days)Females, 70Males, 70Females 2 -Males, 2Number212211115221stweek1115310245151016226224322dweek311216650*6183dweek37159i7i4thweek352i30Averageper adultper week26.826.729.510.19.010.016.017.312.410.516.0Vol. XIV, No. 3, March, 1952 531LABORATORY CULTUREHeretofore staphylinid larvae have been reared in individual salvetins—a laborious method—to prevent cannibalism. This method greatlyrestricts the number of adult insects that can be produced for fieldrelease. It was therefore hoped that cannibalism might be largely eliminated in community cultures by supplying the predators with excessnumbers of prey upon which to feed.Promising results were obtained in preliminary experiments utilizingvarious numbers of newly hatched 7". albertisi larvae in battery jar andbeaker units supplied with heavily infested fruits. About 50 per cent ofthe predators survived to the pupal stage when their average density wasone per cubic inch of soil. Weekly examinations showed an average of 8to 10 oriental fruit fly larvae and puparia per cubic inch of soil in theseunits.The need for an abundant food supply made it desirable to find a suitable host insect that would be easier to obtain and to rear in large numbers throughout the year than the oriental fruit fly. Tests were conductedusing house fly maggots. They proved to be an excellent source of foodfor the predators, which developed normally until they reached the quiescent prepupal stage, when the ravenous house fly maggots reversed theirintended role and attempted to attack the prepupae. The continual disturbance by the burrowing maggots caused a high percentage of abortedpupae, and in several tests the maggots actually consumed the staphyli-nids. Subsequent tests with house fly puparia and with inactivated maggots that had been killed by immersion in hot water were also unsuccessful.The possibility of using larvae of the melon fly, Dacus cucurbitaeCoquillett, was then investigated. Eggs were readily deposited in cucumbers that had been punctured with a dissecting needle, and when themelon fly larvae were nearly mature the cucumbers were split open andplaced on the soil in the breeding units. It was soon noticed that, despitethe use of sterile soil, many of the staphylinid larvae were infested withsmall brownish mites, which sometimes almost completely covered thelarval epidermis. When numerous they prevented the normal moulting ofT. albertisi larvae, causing high mortalities and many aborted pupae.These mites were identified by I. M. Newell, of the University of Hawaii,as the hypopi, or migratory nonfeeding stage of Anoetus (Histiostoma)sp., a common soil-inhabiting scavenger.Tests with several acaricides showed that the mites could be effectivelycontrolled by lightly spraying the cucumbers with a 5 per cent solutionof benzyl benzoate and mixing about 1 gram of DMC3 with each 1,000cc. of soil. Neither material was fully effective when used alone, andhigher concentrations were toxic to the predators.An attempt was then made to mass-culture T. albertisi in standardmetal holding boxes of the type in use at the Oriental Fruit Fly Laboratory. The boxes were 17 inches long, 13 inches wide, and 6 inches deep,and each contained about 314 inches of sterile soil covered with a 1-inch3 Dimethylcarbinol.532 Proceedings, Hawaiian Entomological Societylayer of peat moss, to absorb excess moisture from the infested cucumbers.Acaricides were applied as indicated above, and from 200 to 400 staphyli-nid eggs were evenly distributed beneath the layer of peat moss in eachbox. New heavily infested cucumbers were added each week until thepredators had pupated (about 30 days later), when the boxes were dismantled and the pupae were removed and placed in ice-cube-tray compartments on moist sand under glass, to await adult emergence.Even with an excess of food, the predator larvae tended to congregatein the corners of the large holding boxes where they sometimes attackedone another. Removable metal baffles forming 3 and 6-cubic-inch compartments were placed in the boxes, but these failed to increase the survival rates and were later discarded. About 38 per cent of the staphylinidssurvived to the pupal stage in these units, as compared with approximately 75 per cent in the individual salve tins. However, this loss wasmore than offset by the saving in labor and greater overall efficiency ofthe mass-culture method.Stock.supplies of adult beetles of T. albertisi were kept in large batteryjars half-filled with moist sterile soil covered with a 1-inch layer of peatmoss and provisioned with heavily infested fruits. Eggs were removed eachweek, using a sieving and flotation technique, to prevent their destruction by newly hatched larvae. The soil was gently washed through successive 4-, 16-, and 32-mesh screens, which removed the adult beetles anddebris on the first and- second screens. The eggs and smaller particlesremaining on the third screen were then placed in a saturated brinesolution in a large shallow pan, where the eggs promptly floated to thesurface. They were then skimmed off with a small 32-mesh screen scoopand were immediately rinsed in fresh water. Hatching of these eggsaveraged 71 per cent, as compared with 74 per cent when the eggs weresieved but not placed in brine, and 79 per cent when they were collectedby hand without either sieving or flotation on brine. About 20 per centmore eggs could be recovered by the sieving and flotation technique thanby the former method of visual inspection.LIBERATIONSA total of 1,015 adults and 2,198 eggs and larvae of T. albertisi rearedduring these investigations were liberated in the Waiahole, Waimanaloand Moanalua guava area's on the island of Oahu from July 6 to November 10, 1950. Establishment was encouraged by placing the insects in largepiles of infested guavas in favorable locations containing an abundantsequence of fruiting species. Although evidence of breeding was noted atthese sites for several weeks after liberation, no recoveries have since beenmade and T. albertisi is not known to be established in Hawaii.LITERATURE CITEDFauvel, A. 1877. Les Staphylinides de FAustralie et de la Polynesie. Ann. Mus. Civ.Genova 10:246.Mank, Helen G. 1923. The biology of the Staphylinidae. Ent. Soc. Amer. Ann. 16:220-237.

The Biology and Laboratory Culture of Thyreocephalus albertisi (Fauvel) in Hawaii

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The Biology and Laboratory Culture of Thyreocephalus albertisi (Fauvel) in Hawaii

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