VOLUME 28, NUMBER 2 131

POTENTIAL FECUNDITY OF RHYACIONIA NEOMEXICANA ( DYAR) (OLETHREUTIDAE) RELATED TO PUPAL SIZE

DANIEL T. JENNINGSl

Adult size and weight have been related to female fecundity for a number of . Weight of emerging is positively corre­ lated with numbers of eggs deposited for Ephestia elutella Hubner (Waloff, Norris & Broadhead, 1948). Because weight may vary greatly with age and with environmental conditions such as temperature and humidity, more intrinsic and stable indicators of size are desirable. Wing length, a more constant indicator of moth size than body weight, has been used as an indicator of fecundity for Crambus harpipterus Dyar and Agriphila plumbifimbriella Dyar (Crawford, 1971), and for Oncopera intricata Walker (Martyn, 1965). Pupal size was used as an indicator of fecundity by Williams (1963) for Proceras sacchariphagus Bojer and by Miller (1957) for Choristo­ neura fumiferana (Clemens). Johnson (1968) used the same approach as Miller to establish the relationship between pupal size and fecundity of C. pinus Freeman. In these instances, adult moths were reared from measured pupae and allowed to deposit their eggs. The amount of oviposition in turn was related to pupal size. This approach has the advantage that once the relationship between oviposition and pupal size has been determined, then fecundity can be estimated from empty pupal cases after moth emergence. Disadvantages include problems associated with rearing pupae to adulthood, and ovipositional per­ formance of emerging females. A count of the developing oocytes in pupae approaching eclosion offers a possible index of potential fecundity. The present study was designed to determine if potential fecundity could be estimated from overwin­ tering pupae of Rhyacionia neomexicana (Dyar). This paper relates oocyte complements of R. neomexicana pupae to two measures of pupal r size.

METHODS R. neomexicana overwinters as pupae enclosed within cocoons. Co­ coons are attached to the root collars of host trees, Pinus ponderosa Laws., an average of 2.63 ± 0.90 cm (n = 67) beneath the soil surface.

1 Research Entomologist, u.s. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, with central headquarters maintained at Fort Collins in cooperation with Colorado State University; author is located at Albuquerque in cooperation with the University of New Mexico. 132 JOURNAL OF THE LEPIDOPTERISTS' SOCIETY

Fig. 1. Female Rhyacionia neomexicana pupa showing two measures of pupal size: ( a) linear distance from anterior edge of frontal horn to apex of right wing pad, and (b) width of 5th abdominal segment.

A sample of overwintering pupae was dug 26 March 1970 about 10 days before initial male emergence and 20 days before initial female emer­ gence. Cocoons were dug from the root collars of a natural stand of young pines on the Dudley Burn, Chevelon Ranger District, Coconino County, Sitgreaves National Forest, Arizona. They were placed in an ice cream carton with moist soil, transported to the laboratory (Al­ buquerque) in an ice chest, and stored in a refrigerator (ca. 5°C) until dissected. In the laboratory, the cocoons were opened and pupae sexed by location VOLUME 28, NUMBER 2 133

400

350

300

fJ) CD >. 0 :0 0 250 c ;§ Y=205.9x-156.4 200 r= 0.82

150

1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Fifth abdominal segment width (mm) Fig. 2. Total oiicytes of Rhyacionia neomexicana pupae as a function of abdominal segment width.

and configuration of the genital pore. Live female pupae were mea­ sured to the nearest 0.1 mm using a dissecting microscope equipped with an ocular micrometer. Two measurements were made on each pupa: ( 1) the linear distance from the anterior edge of the frontal horn to the apex of the right wing pad (Fig. 1a), and (2) the maximum width of the 5th abdominal segment (Fig. 1b). The 5th segment is completely free of the wing pads, and remains intact after adult emer­ gence. Measured pupae were heat killed with a flamed dissecting needle and partially embedded in paraffin to facilitate dissection. Specimens were flooded with physiological saline, and the 8 chains of developing ova (ovarioles) removed. To minimize possible differences in oocyte complements due to age or time of development, all pupae (n = 20) were killed and dissected within a 3-day period (30 March-1 April). Ovarioles from the 1st 10 pupae dissected were stained with Grenacher's Borax Carmine to differentiate ripe from unripe oocytes (Crawford, 1971; Williams, 1963). For staining, ovarioles were submerged in the staining solution for 5 minutes, then de-stained by washing in 70% ethanol for 20-30 seconds. Ovarioles from the 1st 10 pupae were stained 134 JOURNAL OF THE LEPIDOPTERISTS' SOCIETY

400

300

II) ~ :>. u :0 0 250 C ~ • Y= 102.6x - 237.5 200 r=0.80

150

4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6.0 6.1 Frontal horn-wing tip length (mm) Fig. 3. Total oiicytes of Rhyacionia neomexicana pupae as a function of frontal horn-wing tip length. and their oocytes counted on the day of dissection, while ovarioles from the 2nd group of 10 pupae were stored in 70% ethanol and counted ( unstained) at a later date. Only discrete, differentiated oocytes were counted. Undifferentiated, developing oogonia in the germarium were not included. Regression analyses were run to determine the relationship between oocyte complement and 5th abdominal segment width and frontal horn-wing tip distance. The resulting equations were tested for the varia­ tion in Y explained by the fitted line at F .ol with ;18 df.

RESULTS All ovarioles (n = 80) in the 1st series of 10 pupae contained de­ veloping oocytes that retained the stain, indicating the chorions im­ pervious to the stain had not yet developed. Mean width of the 5th abdominal segment in dissected pupae was 2.18 ± 0.20 mm, and mean frontal horn-wing tip distance was 5.17 ± 0.40 mm. Total oocytes ( 5,869) had a calculated mean of 293.45 ± 50.99 per pupa (range 194-377). VOLUME 28, NUMBER 2 135

Both regression equations (Figs. 2 and 3) were highly significant, P < 0.005. Thus, a reasonable estimate of oocyte complement for over­ wintering R. neornexicana pupae can be obtained from measures of pupal size. The equations indicate an increase of about 20-21 eggs per mm of abdominal width or frontal horn-wing tip length. The abdominal width measure may be more useful than the frontal horn-wing tip measure for estimates of potential fecundity. The 5th abdominal segment remains intact after adult emergence while the frontal horn-wing tip unit is ruptured and displaced during eclosion.

DISCUSSION Large overwintering R. neomexicana pupae as a rule have more oocytes in their ovarioles than do small pupae. Regression equations demonstrate the linear relationships between pupal size and numbers of oocytes found in the ovarioles. However, oocytes in the pupal stage must be considered only as potential fecundity because additional oocytes may be differentiated after adult emergence, and some oocytes may be reabsorbed. Waloff et al. (1948) found that most of the eggs produced by Ephestis elutella Hubner were present at the time of adult emergence, but that virgin females reabsorbcd 40% and fertilized females reabsorbed 17% of their egg rudiments. An 11% reabsorption of unripe eggs in the ovaries has been reported for Proceras sacchariphagus Bojer (Williams, 1963). Other factors which may influence egg production are; availability of water and nutrients to emerging adults (Waloff et al., 1948; Williams, 1963); density and nutrition of larval populations (Martyn, 1965; Miller, 1957); mating condition of females, i.e., virgin vs. fertilized (Williams, 1963); environmental effects on oviposition, survival, and longevity of females (Waloff et al., 1948); environmental effects on larval stages (Cook, 1961; Tantawy & Vetukhiv, 1960); and changes in the genetical constitution (Willington, 1964). These factors should be considered and explored before assigning a mean fecundity to a population.

LITERATURE CITED COOK, L. M. 1961. Influence of larval environment on adult size and fecundity in the moth Panaxia dominula L. Nature, Lond. 192 (4799): 282. CRAWFORD, C. S. 1971. Comparative reproduction of Crambus harpipterus and Agriphila plumbifimbriella in Northern New Mexico. Ann. Entomol. Soc. Amer. 64: 52-69. JOHNSON, S. A. 1968. Biotic environmental effects on the fecundity of jack pine budworm. MF Thesis, Univ. Mich. School of Natural Resources, 62 p . MARTYN, E. J. 1965. Studies on the ecology of Oncopera intricata Walker (Lepidoptera: ). I. Fecundity of the female moths. Aust. J. Zoo!. 13: 801-805. 136 JOURNAL OF THE LEPIDOPTERISTS' SOCIETY

MILLER, C. A. 1957. A technique for estimating the fecundity of natural popu­ lations of the spruce budworm. Can. J. Zoo!. 35: 1-13. TANTAWY, A. O. & M. O. VETUKHIV. 1960. Effects of size on fecundity, longevity and viability in populations of Drosophila pseudoobscura. Amer. Nat. 94: 395-403. WALOFF, N., M. J. NORRIS & E. C. BROADHEAD. 1948. Fecundity and longevity of Ephestia elutella Hubner (Lep. Phycitidae). Trans. Roy. Entomo!' Soc. Lond. 99: 245-267. WELLINGTON, W. C. 1964. Qualitative changes in populations in unstable environ­ ments. Can. Entomol. 96: 436-451. WILLIAMS, J. R. 1963. The reproduction and fecundity of the sugar cane stalk borer, Proceras sacchariphagu8 Bojer (Lep. Crambidae), p. 611-625. In J. R. Williams (ed.), Proceedings of 11th Congress of the I.S.S.C.T., Mauritius, 1962. Elsevier, Amsterdam.

NOTES ON THREE SPECIES OF HEMILEUCA (SATURNIIDAE) FROM EASTERN OREGON AND CALIFORNIA

NOEL McFARLAND P.O. Box 475, Ceraldton, Western 6530

The information in this paper has been extracted from notes recorded by the author between 1962 and 1964. As basic information on the larvae of H. n. nuttalli and H. h. hera apparently still remains to be published (Ferguson, 1971, p. 137-147), it seems worthwhile to publish these notes without further delay. The larval descriptions that follow remain valid, despite the passage of time, although it is quite con­ ceivable that one or more of the localities mentioned has since been altered (perhaps even obliterated) by those activities of Homo sapiens popularly termed "development" and "progress."

H emileuca (Pseudohazis) nuttalli nuttalli (Strecker) In late April 1962, more than 100 completely-black and unmarked H emileuca larvae (of the subgenus Pseudohazis), in various instars from quite small (second or third instar) to nearly fullgrown, were given to me by Ken Goeden, who collected them on 25 April 1962, near the highway in low hills between 11 to 13 mi. west of Vale, Malheur Co., Oregon (elevation about 2800 ft.). He found them resting and feeding on bitterbrush, Purshia tridentata (Pursh) DC. (Rosaceae), which was