Scelio spp. are important parasites of grasshopper eggs in many countries of the world. However, no information regarding these species is available for Pakistan. Therefore, a study was undertaken to record incidence, distribution, and biology of important species of Pakistan during 1970–74. Some species of Scelio such as S. hieroglyphi, S. sp. ? mauritanicus, Scelio sp. B and C, S. sp. nr. popovi, and Scelio sp. A are restricted in distribution; the first four species are host specific while others can parasitize many hosts. S. aegyptiacus, S. sp. nr. serdangensis, and S. sp. ? tristis are polyphagous and found in many areas of Pakistan. Mortality ranging between 3% and 69% of grasshopper eggs due to factors other than parasitism also occurs. Large sized egg-pods are partially parasitized as grasshopper nymphs also emerge along with the parasites, whereas in pods with fewer eggs nothing except the parasites emerge and are called fully parasitized. Of the nine species of Scelio reared from 3708 egg-pods of 16 grasshopper species, biology of S. aegyptiacus, S. hieroglyphi, and Scelio sp. A was studied which is almost identical in all the species. Immature stages comprising egg, 2 larval instars, and pupa of S. aegyptiacus are developed at 31.5°C ± 3 in 2–3, 10–11, and 7–8 days respectively. The female has the capacity to lay 121–135 eggs. Prior to oviposition, mating lasting 1–2 min takes place and a hole is drilled in the froth-plug. Freshly laid egg-pods are preferred over old during parasitization.

The photoperiodic reaction in North American codling moth populations displayed clinal-type variation similar to populations in Europe. A latitudinal shift of 10° to the north corresponded to an increase of 1.25 h in the critical photoperiod. Intrapopulation variance in diapause response appeared to be similar in populations of different origin. The critical photoperiod was not constant for a geographic population but varied between years probably due to the modifying effect of prediapause temperatures. In Michigan and other areas in the northeastern United States with similar climate the codling moth is essentially bivoltine with considerable yearly variability in second generation emergence. A graphic model is presented which gives an estimate of voltinism and the proportion of diapausing first-generation larvae based on the seasonal heat unit total at the time of diapause initiation. From an analysis of original data and historical phenological records an algorithm was developed which describes the relationship between effective temperatures and the variance of second generation emergence and which can predict population curves for climatically different years. Use of this predictive method in conjunction with monitoring information provided by a pheromone trap is discussed.

Xenoborus Reuter is synonymized with Tropidosteptes Uhler. Tropidosteptes brooksi n. sp. is described from Saskatchewan, Manitoba, Ontario, and Quebec. The species was collected on Fraxinus spp.

The process of re-emergence of Dendroctonus frontalis parent adults was investigated using emergence traps placed systematically along the bole of infested loblolly pine, Pinus taeda. Daily collections of the traps showed the re-emergence pattern by height through time. Re-emergence/100 cm2 (Y) was described as a function of time (X) by the model Y = C(18X)B−1 exp (−A(18X)B) + ɛε for intervals along the infested bole. Peak re-emergence occurred shortly after peak attack density and continued 16–20 days. Highest re-emergence density occurred at the midportion of the infested bole and tapered to the ends. The same model was used to describe re-emergence as an average process for the entire tree. For convenience in evaluating expected re-emergence totals over a time span, the cumulative form of the model was fit to the data. The proportion of re-emergence was studied using bark samples taken at the beginning and end of the process and was found to be 97% of the attacking adult population. An empirical distribution function was developed and the probability of re-emergence described using the function Y = ABCXB−1 exp (−AXB) + ɛε, where Y = the probability of re-emergence at a time X in days given that a beetle was present on day 1 of the process. The cumulative form of this model was also provided.

Using laboratory bioassays parent adults were tested and found to respond to the attractant mixture of frontalin, trans-verbenol, and loblolly pine turpentine.

Re-emergence may play several functions in the population dynamics of D. frontalis: conditioning host trees through mass colonization; establishing brood populations through multiple re-emergence, thereby efficiently allocating egg populations; identifying new hosts and aggregating populations through pheromone production; and maintenance of continuity in pheromone production at the active portion of the infestation, thereby identifying the location of trees under colonization. The prolonged re-emergence period was suggested to be of survival value to the insect in that local short term disasters would affect only a small proportion of the re-emerging population. The number of re-emergences and proportions of re-emergence were suggested to be related to oviposition per parent adult and hence attack density.

The formation of a yellow band inside the stalk of each ovariole was a good indicator that a female European corn borer had laid eggs. The absence of these bands was less reliable as an indicator that no eggs had been laid, probably due to the time taken for the bands to form. The numbers of moths accumulating in a light trap over a week at Harrow, Ontario, and the numbers of females estimated to have laid eggs correlated significantly with the numbers of larvae developing in nearby green pepper plots 3, 4, and 5 weeks later during second generation flights. This enabled linear equations for forecasting pepper damage to be developed, in which the dissection data was more useful than the total moth catch alone.

Male moths of Aegeria tibialis Harris, a lepidopterous pest of poplar cutting beds in nurseries, were strongly attracted to virgin females and to mixtures of Z3, Z13-octadecadien-1-ol and its acetate. Extracts of female abdominal tips yielded two fractions stimulatory to male antennae. These fractions corresponded to a C18 alcohol and a C18 acetate. Electroantennogram measurements using synthetic chemicals demonstrated that appreciable male antennal stimulation occurred only with C18 compounds having Z-unsaturation at positions 3 or 13, indicating that the synthetic sex attractant may be the natural pheromone of this species.

Achyra llaguenalis n. sp., from western Peru, is described. Its relationships are briefly discussed and a key is given to known American species of the genus.

Two manners in which parasitic Hymenoptera gather reproductive proteins are described. Hydropic species gather all protein necessary for reproduction as larvae. Only 5–10% of the material necessary to form a viable first instar larva is put into each egg; the remainder is gathered by the egg within the host. Egg storage is in the lateral oviducts, handling times are short and egg production is independent of host density. Three Bathyplectes spp. are examples of hydropic parasitoids. Anhydropic species gather some or all protein as adults, often by host feeding. All the material necessary for the formation of a viable first instar larva is stored within the egg. The eggs are held in the ovary until laid. Handling times are longer and continued egg production is dependent upon host density. Tetrastichus incertus (Ratzeburg) is an anhydropic parasitoid.

Hydropic parasitoids appear best suited for biological control efforts in ephemeral situations (i.e. cotton or alfalfa). Anhydropic parasitoids appear best suited for biological control efforts in stable situations (i.e. citrus or walnuts).

A simple population model is used to test the hypothesis that Douglas-fir tussock moth population cycles are caused by time-delays in the responses of density-dependent (negative feedback) processes. The limited data that are available do not seriously conflict with this hypothesis.

Colonies of P. fuscatus that were initiated by various numbers of foundresses were studied to gather basic life table information. This information was used to estimate the selective advantage of foundress association according to a kin selection model, a parental manipulation model, two individual selection models, and a combined kin and individual selection model. Life table data were obtained for colonies located in exposed nest sites and for colonies located in nest sites provided with protection from vertebrate predators. Relative productivity of colonies produced by different size foundress associations and under different levels of predation pressure were determined. Multiple foundress colonies were found to be more productive and have an increased ability to re-establish after an episode of predation when compared with single foundress colonies. When predation levels on the colonies were high, multiple foundress colonies were more productive per colony and per foundress. When predation levels on the colonies were low, multiple foundress colonies were more productive per colony but less productive per foundress. At high levels of predation, when the queens and joiners were all assumed to have equivalent potential productivities, the kin selection model, the parental manipulation model, and the combined kin and individual selection model all predicted a selective advantage for joiners in foundress associations. At low levels of predation, when the wasps are assumed to have equivalent productivities, only the parental manipulation model predicted a selective advantage for joiners in foundress associations. When the assumption of equivalent potential is relaxed and when the wasps are assumed to be capable of detecting and acting upon individual differences in productivity, then all of the models could account for the existence of foundress associations. However, under this last set of assumptions the individual selection models require that the joiners have very low potential productivities.

Ligation experiments were conducted on freshly-ecdysed pupae of Neodiprion sertifer (Geoff.) to help identify sources of hormones which might control development of cuticle, rate of heartbeat, egg production, and uric acid depletion in adult females. Ligatures behind the head or thorax have little or no effect on apolysis of abdominal cuticle. Cuticle tanning and initiation of yolk formation are inhibited exclusively by ligatures behind the thorax. Increase in heartbeat rate and ovary weights is inhibited slightly by ligatures behind the head and almost completely by those behind the thorax. Uric acid depletion is inhibited equally by both ligations. The results are discussed in relation to current knowledge of the anatomy of endocrine organs in sawflies and insect endocrine functions in general.

Adults of Camisia labradorica, n. sp., from Labrador are described. They are closely similar to those of C. lapponica (Trägårdh, 1910), but are distinguished by the shape of notogastral setae and number of genital setae.

When new laid eggs of the house cricket are treated with a potassium biphthalate buffer (0.05 M) at pH 4.01 for 1 h, followed by a Na2CO3 solution at pH 11.0 for 22 h at room temperature, the chorion lifts off the surface of the egg; by cutting off the end of the stretched chorion, the dechorionated egg may be pushed out of the shell. Dechorionated eggs behave in a different manner towards sucrose and salt solutions than do intact eggs. These and other experimental results are discussed in relation to the physiology of water absorption.

Southern pine beetles, Dendroctonus frontalis Zimmerman, often carry mites as they emerge from host trees. At least 14 species of mites are phoretic (Moser and Roton 1971). But for D. frontalis, it is not clearly known where in the host tree and at what stage of the beetle's development the mites attach themselves. After the beetle larvae construct oval feeding cells, they develop in three stages: pupa, callow adults, and brood adults (Fig. 1). In trees with thick bark, the larvae bore into the outer bark from within, construct pupal cells, and pupate. But in trees with thin bark, the larvae pupate directly in the larval cells next to the xylem. Thus, the larval galleries in either case are in the living phloem adjacent to the sapwood.

The water boatman Cenocorixa expleta (Uhler) is an inhabitant of saline ponds in the interior of western North America (Jansson 1972; Scudder 1976). In a field survey, Scudder (1969a) failed to find this species in ponds with surface conductivities less than 3900 μmhos/cm. Although it is apparently absent from fresh water, the osmotic responses of C. expleta are essentially those of a fresh water insect (Scudder et al. 1972). Also, salinity tolerance experiments carried out by Scudder (1969b) show that at 15°C adults of the species can survive almost a month in fresh water (less than 800 μmhos/cm) without food. However, it has not been shown that C. expleta can actually develop and breed successfully in fresh water.