Late Instar Nymphs Research Articles

The Biology of Encarsia tricolor: An Autoparasitoid of Whitefly

Abstract Encarsia tricolor Forster (Hym.: Aphelinidae) is an autoparasitoid of a number of whitefly pest species. Females develop as primary endoparasitoids, whereas males develop hyperparasitically in other whitefly endoparasitoids including conspecific females. Under a constant regime of 25°C and 16:8 h L:D, the biology of E. tricolor was investigated using the Cabbage whitefly, Aleyrodes proletella, as host. The following results were obtained. (1) A significant positive linear correlation was detected between size and longevity for both sexes, given a honey diet. Mean (±SE) longevity was 16.9 ± 0.62 days for females and 13.8 ± 0.66 days for males. Females were significantly larger than males. (2) Female E. tricolor could develop in all host instars. Development times were slowest in first instar nymphs (22.3 ± 0.34 days) and fastest in fourth instar nymphs (18.7 ± 0.25 days). Female development times were not overtly variable. (3) Male E. tricolor could hyperparasitize all stages of conspecific female larvae and pupae offered. When parasitizing larvae, male development times were longer, indicating that male development is delayed until the host approaches pupation. (4) Mean (±SE) lifetime fecundity of E. tricolor laying female eggs was 85.36 ± 13.85 at a mean rate of 7.31 ± 0.27 eggs/female/day. (5) In a study of sex ratio dynamics in the parasitoid culture, emergent sex ratios were a function of the period of parasitism. The emergent sex ratio (percentage male) from individual leaves increased from 44% after 2 weeks in the culture to 76% after 4 weeks. A concurrent increase in the overall percentage parasitism was also recorded: 23 ± 3.4% at 2 weeks to 87 ± 4.1% at 4 weeks. (6) Observations on oviposition behavior indicated a clear preference to exploit late instar nymphs for female production. All whitefly instars were used for host feeding. Oviposition times for male eggs (in conspecific pupae) were significantly greater than for female eggs (in late instar whitefly nymphs).

Differential Susceptibility of German Cockroach (Dictyoptera: Blattellidae) Sexes and Nymphal Age Classes to Insecticides

Sexes and nymphal age classes of insecticide-susceptible and resistant strains of the German cockroach, Blattella germanica (L.), were evaluated for susceptibility to bendiocarb, chlorpyrifos, and cypermethrin. In all cases, late-stage nymphs had higher LC50s (µg per insect) and LD50s (µg/mg) than adult males. In most cases, these nymphs were also more difficult to kill than adult females. This reduced susceptibility to insecticides in late-instar nymphs occurred irrespective of weight differences, type of insecticide, or strain of cockroach. Females had significantly higher LC50s (µg per insect) than males for bendiocarb (resistant strain), chlorpyrifos (susceptible and resistant strains), and cypermethrin (susceptible strain). However, LD50s (µg/mg) for males and females were the same for bendiocarb (susceptible and resistant strains), chlorpyrifos (susceptible strain), and cypermethrin (susceptible and resistant strains). Resistance ratios for bendiocarb, chlorpyrifos, and cypermethrin were higher for some life stages and sexes than for others. Resistance ratios were 6-10 for bendiocarb in adult males and females, but ratios for 4- to 6-wk-old nymphs were 5-100. For chlorpyrifos, the resistance ratio was 7 for males but 20 for females. Males were 32-fold resistant to cypermethrin but 3- to 6-wk-old nymphs were 44-94-fold resistant.

Comparisons Between the Response of German Cockroach Field-Collected Strains (Dictyoptera: Blattellidae) to Vapors and Contact with a Cyfluthrin Formulation

Research on differences in insecticide-induced behavior of German cockroach field-collected strains was continued. Late instar nymphs (5th–6th stadia) were drawn from the Fairbanks, an insecticide susceptible strain, and two pyrethroid resistant strains, the Jacksonville and Forest Green. Dispersal induced by vapors of a cyfluthrin flowable concentrate (FC) and the FC formulation base (blank) was compared with response to the FC and the FC blank when dry. Jacksonville nymphs avoided the dried FC, but not as strongly as Fairbanks strain nymphs. The Al played a major role in eliciting avoidance by Fairbanks strain nymphs but, in the Jacksonville strain, avoidance was due more to an ingredient(s) of the formulation base. Forest Green nymphs did not avoid the dried FC or the FC blank. Vapors of the FC and the FC blank caused rapid dispersal of all strains, but dispersal of resistant strain nymphs was slower than that of susceptible strain nymphs. Although Jacksonville nymphs responded more strongly to the dried formulation than Forest Green nymphs, the response to vapors was weaker than that of Forest Green nymphs. It is suggested that localized populations of the German cockroach have developed many different combinations of behavioral modifications and physiological/biochemical resistance.

Biology of Macropanesthia rhinoceros Saussure (Dictyoptera: Blaberidae)

Field and laboratory observations of Macropanesthia rhinoceros Saussure were undertaken. These cockroaches live in permanent underground burrows and feed on dry leaves and twigs. M. rhinoceros are usually found alone; however, young nymphs remain with their mother for some months and adult males may cohabit with late-instar female nymphs. One brood of ≈20 young is produced each year in late spring after an incubation period lasting ≈3 mo. Nymphal growth is variable and is slower in the laboratory than in the field. Field nymphs reach the eighth instar in ≈5 mo. There are 11-14 nymphal instars and the shortest nymphal period is <3 yr. Adults can survive in the laboratory for 7 yr. After rain, cockroaches may be observed on the soil surface. Adult males are more prevalent than females. Typically, males wander searching for mates while females take litter into their burrows. General aggressiveness of individuals is consistent with a solitary existence. Adult males are highly aggressive towards one another. Females with young are more aggressive than those without young. Courtship behavior is relatively simple and comparable to other cockroaches that live in restrictive habitats.

Safer'S Insecticidal Soap for Pear Psylla Control, 1989

Abstract Treatments were applied to adjacent unreplicated rows of 15 trees. Chemical applications were made with a John Bean 400 gal speed sprayer at 300 psi with a delivery rate of 50 gal/acre. Materials were applied to runoff. In both treatments, oil at 1 gal/100, was applied on 25 Apr and 23 May. Polyram 80 WP at 1-1.5 lb/100, was applied on 14 Apr, 25 Apr, 23 May, 5 Jun, 27 Jun, 17 Jul, 24 Jul and 9 Aug. Guthion 35 WP at 0.63 lb/100 was applied at petal fall (23 May). In the standard block, Imidan 50 WP at 1 lb/100 was applied on 5 Jun and 27 Jun for plum curculio control and Mitac 1.5 EC was applied at 1.5 pt/100 on 17 Jul, 24 Jul and 9 Aug for pear psylla control. Safer's Insecticidal Soap at 2 gal/100 was applied to the treatment block on 26 May, 24 Jul, 9 Aug and 22 Aug for psylla control. Early instar and late instar pear psylla nymphs were counted from the first fully expanded leaf from 5 succulent terminals (as available) on 10 trees in each block. At harvest, 300 pears from each treatment were examined for phytotoxicity, and insect and disease damage.

The influence of nymphal and adult dietary protein on food intake and reproduction in female brown‐banded cockroaches

AbstractFemale brown‐banded cockroaches, Supella longipalpa (F.) (Dictyoptera: Blattellidae), failed to elevate consumption rates when fed a 5% protein diet compared with females fed either 25% protein or commercial rat food. Adult performance was directly influenced by dietary protein level: Females fed 65% protein died rapidly, while in females fed 5% protein feeding and reproductive rates were reduced after production of three oothecae. In females fed a low protein diet as both late instar nymphs and as adults, mating was delayed and they required more time to form oothecae than females switched to 25% protein as adults. The role of nymphal reserves in adult reproduction is discussed.RésuméInfluence des protéines contenues dans l'alimentation larvaire et imaginale sur la prise d'aliments et la reproduction de Supella longipalpaLa consommation et la reproduction de S. longipalpa ont été examinées lors de la consommation d'aliment standard pour rat et de régimes artificiels contenant 5, 25 et 65% de protéines. Les femelles élevées sur régime à 5% de protéines ne consomment pas plus et leur reproduction est significativement inférieure à celle de femelles élevées sur aliment standard ou a 25% de protéines; après la production de 3 oothèques, la reproduction de ces femelles se ralentit, leur consommation diminue et les oothèques deviennent plus petites que celles des femelles élevées sur un régime à 25% de protéines. Nous supposons que les premiers cycles reproductifs de ces femelles ont été assurés avec les réserves accumulées pendant la vie larvaire. Les femelles alimentées sur régime à 5% de protéines à la fois pendant le dernier stade larvaire et pendant la vie imaginale ont besoin de beaucoup plus de temps pour s'accoupler et pour produire des oothèques que les femelles alimentées sur régime à 5% pendant le dernier stade larvaire et transférées adultes sur un régime à 25% de protéines. Ainsi, les réserves larvaires sont une ressource importante améliorant la reproduction des adultes ayant un régime pauvre en protéines. Cependant, le passé alimentaire larvaire a peu d'effet sur la reproduction des adultes alimentés convenablement.

Effects of wing‐pad removal and corpus allatum implantation on development of wings, flight muscles, and related structures in the striped ground cricket, Allonemobius fasciatus

ABSTRACT. Removal of a hindwing pad from late instar nymphs of the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae) inhibits the formation of long‐winged adults. All nymphs become short‐winged when their hindwing pad is removed during the sixth (penultimate) instar or during the first 2 days of the seventh instar. When a hindwing pad is removed on day 4 of the seventh instar or later, there is no effect on wing development and at least 50% of the crickets emerge as long‐winged adults as in controls.The period sensitive for removal of a hindwing pad varies among different structures, e.g. elytra, hindwings, flight muscles, and the acrotergite of the first abdominal segment. As a result, some intermediate forms are produced when a hindwing pad is removed in the middle of the seventh instar.Implantation of corpora allata (CA) into late instar nymphs also inhibits formation of long‐winged adults. When CA are implanted on day 2 or 3 of the seventh instar, some of the resulting adults have abnormally short elytra. Implantation of CA at an earlier stage produces supernumerary (eighth instar) nymphs.

New Host Plant Records for the Stink Bug Piezodorus guildinii in Florida (Hemiptera: Pentatomidae)

Piezodorus guildinii (Westwood) is a neotropical pentatomid that occurs from the southern United States to Argentina. This species is a serious pest of soybean throughout South America, particularly in Brazil (summarized in Panizzi and Slansky 1985a). It was commonly found on soybean during 1983 in north-central Florida (A. R. Panizzi, unpublished observations), where its abundance in the past few years seems to have increased (Menezes 1981), suggesting that it potentially could become a serious soybean pest in Florida. P. guildinii is polyphagous; reported host plants include a number of wild and cultivated species, many of which are legumes (e.g., alfalfa, lentil, green bean and soybean; summarized in Panizzi and Slansky 1985a). However, some of these plants may only provide a substrate for resting or refuge and may not actually be host plants. We found eggs, nymphs and adults of P. guildinii on 3 apparently unreported host plants during November and December, 1983 in Alachua County, Florida. These plants were: Indigofera hirsuta L., Crotaclaria lanceolata E. Mey., and Crotalaria brevidens Benth. On the first two species, egg masses were observed on pods; nymphs (lst through 5th instars) and adults were found most frequently feeding and/or basking on pods. Late instar nymphs and adults would hide among the pods when disturbed, and as many as 20 individuals were found on a single host plant. On the third species, only one 5th instar nymph was found (feeding on a pod). Subsequent research on adult biology of P. guildinii (Panizzi and Slansky 1985b) indicated that pods of I. hirsuta, and to a lesser extent C. lanceolata (C. brevidens was not included in our study) allow early oviposition and increased fecundity compared to adults fed raw shelled peanuts, dry soybean seeds or green (snap) beans. We successfully reared nymphs on I. hirsuta pods but high mortality occurred when reared on green beans (the latter are commonly used as a suitable laboratory food for another polyphagous stink bug, Nezara viridula (L.); Harris and Todd 1980). The broad host plant range of P. guildinii indicates that a number of wild plant species could serve to maintain its populations when cultivated host plants are unavailable, and provide sources from which colonization of soybean and other cultivated hosts occurs. In Brazil, P. guildinii has been recorded on an unspecified species of Crotalaria (Monte 1939). In Colombia,

PATTERNS OF MORPHOLOGICAL AND REPRODUCTIVE VARIATION IN STENONEMA MAYFLIES (EPHEMEROPTERA: HEPTAGENIIDAE) IN EASTERN LAKE HURON

AbstractSignificant variation in the morphology of late-instar nymphs of Stenonema tripunctatum (Banks) in Lake Huron could not be ascribed to their proximity to warm-water plumes originating from the Bruce Nuclear Power Development, by either multivariate or univariate analyses of size and shape. Major sources of variation in S. tripunctatum were developmental state and sex. Nymphs collected just prior to emergence had low values of transverse measurements in anterior regions (inter-orbital width, prothoracic width), whereas males and females were separated by these measurements and other components of head geometry.No significant effects of thermal exposure were found in the reproductive development of S. tripunctatum, but this species is most commonly found below depths at which thermal-plume effects are expected. Based on a small but representative sample, ultimate-instar nymphs of Stenonema vicarium (Walker) from a depth of 3 m contained significantly fewer eggs and allocated a significantly lower proportion of biomass (dry weight) to reproduction in locations with higher temperatures.

EFFECTS OF DENSITY, STAGE, AND SEX OF THE POTATO LEAFHOPPER,EMPOASCA FABAE(HOMOPTERA: CICADELLIDAE), ON SEEDLING ALFALFA GROWTH

AbstractPotato leafhopper,Empoasca fabae(Harris), early-instar nymphs (1–2 instar), late-instar nymphs (3–5 instar), adult males and adult females were caged at various densities on seedling alfalfa cv. Vernal and allowed to feed for 6 days. Feeding by adult females, late-instar nymphs, and adult males retarded plant height, leaf number, and dry weight, about 20 to 50% more than did the early-instar nymphs at most of the leafhopper densities tested, over 6 days. Protein content was affected differently from the other plant parameters; it was reduced most by adult males. This was apparently due to premature death of the plants caused by late-instar nymphs and adult females. The percentage reduction for each of the plant parameters was highly correlated with leafhopper density and was nonlinear, except with the early-instar nymphs. Alfalfa plants exposed to two or four late-instar nymphs or two adult females, significantly increased in height and leaf number during a 7-day recovery period. Plants exposed to four adult females did not recover.

EPIZOOTIOLOGY OF A MICROSPORIDIUM IN FIELD POPULATIONS OF AULOCARA ELLIOTTI AND PSOLOESSA DELICATULA (INSECTA: ORTHOPTERA)

An undescribed microsporidium was isolated from a grasshopper species, Aulocara elliotti Thomas, in Platte County, Wyoming. A subsequent survey of grasshoppers revealed infections of the microsporidium in the other predominant grasshopper species, Psoloessa delicatula (Scudder). In a generation cycle, P. delicatula hatch in mid-summer, overwinter as late-instar nymphs, and become adults and oviposit in late spring, whereas A. elliotti diapause as eggs during winter, hatch in late spring, become adults and oviposit in early to mid-summer. The purpose of the present investigation is to report on the comparative incidence and transmission of the parasite in A. elliotti and P. delicatula.

Evaluation of the role of Microvelia douglasi atrolineata (Bergroth) (Heteroptera: Veliidae) as predator of the brown planthopper Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

SummaryThe biology of the veliid bug M. d. atrolineata, its predatory behavior, and the effects of plural hunting were studied to evaluate its role as a predator of the brown planthopper Nilaparvata lugens in the Philippines. The probability of planthoppers falling onto the water surface and provision of habitat continuity was measured by a sticky trap placed at the base of rice hills in a greenhouse and in paddy fields.The developmental period of immature stages combined was 21 days. If given prey, females laid 25 eggs on the average during an adult life span of 18 days. Starved adults could survive for only 3–5 days.The functional response to prey density was sigmoid, and the maximum number of prey killed was 7 per day. Prey feeding was completed in 12–36 min. The percentage of successful prey attacks averaged 5–8%, decreasing with higher (and larger) developmental. stages of prey, but adult prey were found the soonest. Plural hunting increased the probability of capturing prey by as much as 2.5 times that by individual hunting.Late‐instar nymphs, which may be more active, fell from rice hills in a greenhouse more than early‐instar nymphs, and the number falling increased with density. In the field the percentage of planthoppers falling to the water in 1 day varied considerably, from 1% for nymphs in one field to 67% for adults in another field.On the basis of work described above and given the high density of veliid predators in flooded paddy fields of tropical Asia, M. d. atrolineata is considered one of the most important natural enemies of the brown planthopper.

Alate production and sex ratio in colonies of the Neotropical termite Nasutitermes corniger (Isoptera; Termitidae).

1. Dissections of 49 entire Nasutitermes corniger (Motschulsky) colonies collected in Panama immediately prior to the nuptial flights give data on numbers, biomass and sex ratio of alates produced by individual colonies. 2) Twenty-six other colonies were collected and dissected in the early period of alate nymph development. Alate nymphs proceed through five instars, spending 5-8 months within the parental colony. 3) Even when comparing colonies of similar size, variation in reproductive output among N. corniger colonies in a population is marked. Mature colonies (neuter population size 50,000-400,000) generally produce 5,000-25,000 alates, although some large colonies had no fertile brood, at least during the year they were censused. 4) On average, colonies which produce alates have 35% of the colony biomass invested in alates (or late instar nymphs) shortly before the nuptial flight. 5) Female N. corniger alates are 1.2-1.4 times heavier (dry weight) than male nestmates. Numerical sex ratio among colonies is skewed toward males, while biomass "investment" sex ratio is not significantly different from 1:1. These data conform to Fisher's amended theory of expected sex ratio.

Fescue, Grasshopper Control, Missouri, 1982

Abstract The test was conducted near Alton, MO on ca 13-in fescue. Insecticide sprays were applied on Aug 10 to 60 x 60 ft plots with 4 replications. Grasshoppers were late instar nymphs and adult meadow grasshoppers (80%) and redlegged grasshoppers (20%). Sprays were applied at 20 gpa and 40 psi using 8002 flat fan nozzles on a 20-ft spray boom. Evaluations were obtained at 48 h post treatment by taking 10 (180 degree) sweeps with a 15-in sweep net. The temperature at treatment was 83°F. The data were transformed by X + 0.5. Means in the table are of actual counts

Scanning electron microscopy of Haller's organ in immature stages of (Say) and olenev (acari: ixodida)

Abstract Haller's organ, a chemoreceptor and hygrosensor located dorsally on tarsi l of the Ixodida was viewed in immature stages of Dermacentor variabilis (say) and Ornithodoros tartakovskyi Olenev by scanning electron microscopy (SEM). Larval and nymphal specimens of D. variabilis (Figs. 1, 2) exhibited characteristics differences in overall shape of organ, shape of posterior capsule aperture, shape of anterior trough, number and arrangement of trough sensillae, and shape of the distal transverse wall of the anterior trough. Differences between larvae and late instar nymphs of O. tartakovskyi (Figs. 3, 4) were primarily in trough shape and numbers of sensillae present. Subsurface articulations within the posterior capsule of both Dermacentor ticks were obscured due to the emarginate apertures (Fig. 2). The open apertures found in both stages of Ornithodoros allowed the viewing of numerous digitate processes within the capsule (Fig. 4). A nodiform sensillum (Figs. 3, 4), medially located within the proximal cluster of trough sensillae in O. tartakovskyi , had no similar counterpart in D. variabilis .

Ultrastructure and morphogenesis of the abdominal integumental gland of Schistocerca gregaria forsk. (Orthoptera: Acrididae)

The objective of this research is to describe the morphogenesis and the structures of the abdominal glands in the late 4th and 5th instar nymphs of Schistocerca gregaria. The glands are composed of 4 cells called secretory, ciliary, canal and enveloping cells, according to their morphology and functions. The secretion, stored in the secretory cell in the form of electron-dense granules, is discharged during ecdysis through a cuticular duct, after the ciliary cell has unplugged its opening. The discharge of the secretion is facilitated by the pressure exerted by the hemolymph at ecdysis and by the spreading of the integumental folds. This secretion appears to be involved in the deposition of the cement layer of the cuticle. After ecdysis, the ciliary and enveloping cells die, and their remains are incorporated by the surrounding epidermal cells. The secretory cell begins to synthesize new secretory granules and remains joined with the canal cell, forming a 2-cell secretory unit, which remains functional throughout imaginal life.

Distribution and environmental synchronization of the marine insect, Halobates robustus , in the Galapagos Islands

The following three aspects of the biology of the marine insect Halobates robustus were studied, during a two week observation period, at several sites in the Galapagos Islands: distribution, aggregation behaviour and rhythmicity of locomotory activity. H. robustus occurred in highest numbers on the water surface at shores fringed with mangroves. The aggregations of H. robustus varied according to their location and density. Copulating adults formed dense, floating aggregations, which tended to be close to rocks or mangroves. Late instar nymphs were less aggregated and, in lagoons (where there was some shelter from direct tidal forces), were furthest from the shore. In two types of habitat (mangrove-fringed, sandy shores and rocky shores) the aggregations of H. robustus showed a pronounced ability to maintain a floating station in relation to the surrounding environment, irrespective of tidal movements (in one case at 34 m from the nearest fixed objects). Evidence of the ability of the aggregations to maintain station on the water surface was also obtained by comparing the movements of H. robustus with those of floating polystyrene particles, which move passively with wind and tide. Laboratory observations and experiments indicated no clear periodicity in locomotory movements throughout a 24 h period. However, the frequency of encounters between individuals showed two daily peaks, post-dawn and pre-dusk, with fewer encounters during the day and only occasional encounters during the night. By shifting the light-dark cycle it was demonstrated that the daily bimodal rhythm of encounters is triggered by dawn and, since it is not maintained in constant light or dark, an 'hour-glass' mechanism is suggested. The contributions of single adults, of copulating pairs and of immature stages to the overall pattern of activity were also determined. Immature stages did not affect the overall rate of encounters significantly and the interactions between single and copulating pairs of adults appear to have been responsible for the bimodal pattern.

Evaluation of Insecticides for Western Drywood Termite Control, 1978

Abstract Eight insecticides were tested for effectiveness against field populations of Incisitermesminor collected from native woods and maintained in the laboratory. Whatman No. 1 filter paper, cut into discs (72 cm2) and set into 9.7 cm I.D. uncovered petri dish tops, were treated with insecticide. Dusts were applied by volume (I cc/dish) and liquids were deposited with a pipette with 3 ml excess of dilutant to insure uniform distribution of toxicant. Liquids were allowed to dry 24 hours or age 30 days before being tested. Each bioassay replicate consisted of five late-instar nymphs or alates confined to the treated surface under an inverted 3.2 cm I.D. stendor dish. Continuous exposure was conducted for about 4 weeks in darkness at ca. 22°C and 30-50% R.H. In pilot tests using a single replicate, liquids were screened for activity by using 10-fold serial dilutions applied in a range from 1.0 mg to 10-6 mg ai/cm2. Dilutions producing complete mortality within a few days or showing no mortality within several weeks were omitted from the final bioassay. The final test, shown in the table, was conducted using three replicates for each of the lowest concentrations demonstrating effectiveness and for each dust deposit. Mortality counts were taken several times a week and presence of feeding on the paper was noted at 14 days.

Isolation and identification of the metabolites of 22,25 dideoxyecdysone from cockroach fat body cultures

Hydroxylation and conjugation were the principal pathways of metabolism of 22,25-dideoxyecdysone in cockroach fat body cultures. The major metabolite isolated and identified was the tetrahydroxy steroid 22-deoxyecdysone; other exdysteroids isolated, in order of decreasing quantities, were 22-deoxy-26-hydroxyecdysone, 22,25-dideoxy-26-hydroxyecdysone, and 22-deoxy-20-hydroxyecdysone. Cockroach fat body from late-instar nymphs appears to lack the mechanism for hydroxylating at C-22. Radioanalyses of the material obtained from enzymic hydrolysis of the conjugate fraction showed 65, 15 and 20% of tetraols, pentaols, and unhydrolyzed conjugates respectively, and no 22,25-dideoxyecdysone. An azasteroid and two nonsteroidal amines that effectively inhibit the activity of 22,25-dideoxyecdysone in the cockroach leg regenerate-fat body culture system enhanced the metabolism of 22,25-dideoxyecdysone, decreased the quantity of the pentaol fraction present, and caused an increase or accumulation of the tetraol and conjugate fractions in the fat body culture system.

Isolation and identification of the metabolites of 22,25-dideoxyecdysone from cockroach fat body cultures.

Hydroxylation and conjugation were the principal pathways of metabolism of 22,25-dideoxyecdysone in cockroach fat body cultures. The major metabolite isolated and identified was the tetrahydroxy steroid 22-deoxyecdysone; other exdysteroids isolated, in order of decreasing quantities, were 22-deoxy-26-hydroxyecdysone, 22,25-dideoxy-26-hydroxyecdysone, and 22-deoxy-20-hydroxyecdysone. Cockroach fat body from late-instar nymphs appears to lack the mechanism for hydroxylating at C-22. Radioanalyses of the material obtained from enzymic hydrolysis of the conjugate fraction showed 65, 15 and 20% of tetraols, pentaols, and unhydrolyzed conjugates respectively, and no 22,25-dideoxyecdysone. An azasteroid and two nonsteroidal amines that effectively inhibit the activity of 22,25-dideoxyecdysone in the cockroach leg regenerate-fat body culture system enhanced the metabolism of 22,25-dideoxyecdysone, decreased the quantity of the pentaol fraction present, and caused an increase or accumulation of the tetraol and conjugate fractions in the fat body culture system.