Bionomics of two aspen bark beetles, Trypophloeus populi and Procryphalus mucronatus (Coleoptera: Scolytidae)

Beetles of Trypophloeus populi attacked green bark of unhealthy aspen ( Populus tremuloides ) and hastened the death of the tree. Beetles of Procryphalus mucronatus favored dead bark and were of little significance in the death of the aspen. These two beetle species were distinguished from each other by their primary galleries, eggs, larvae, larval mines, and mating behavior. In T. populi, there were three larval instars and one to one and one - half generations per year; only larvae overwintered, and the eggs of the first generation were present by mid - July. In P. mucronatus, there were two larval instars and one and one - half to two generations per year; both larvae and adults overwintered, and the first eggs of the new season were present by late May.     

Growth and reproduction of the flannelmouth sucker, Catostomus latipinnis, in the Upper Colorado River Basin, 1975-76

Growth rates estimated using the scale annuli of flannelmouth sucker, Catostomus latipinnis , did not differ between fish collected from the Gunnison and Colorado rivers, and the Green and Yampa rivers. However, body condition and fecundity were significantly greater in the former population. Age of first maturity for male and female fish from all rivers was IV; and most fish were mature by age VII. The smallest mature female collected was 405 mm, and the smallest mature male was 391 mm total length. Fecundity ranged from 4,000 ova in fish 450 mm long to 40,000 ova in a 500-mm fish: mean ovum diameter was 2.39 mm. Ripe male flannelmouth suckers were collected from early April through June; ripe females were collected from both study areas during May and early June.         

Spawning chronology and larval emergence of June sucker ( Chasmistes liorus )

June sucker ( Chasmistes liorus ) spawned in the Provo River, Utah, over a 2-wk period in early June during both 1987 and 1988. Emergent larvae emigrated from the river to Utah Lake over a 2- to 3-wk period. Drift into the lake peaked between 1200 and 0400. During daylight hours, emergent larvae tended to occur in pools. Peak emergence of larval drift was approximately 1.2 larvae/m 3 during late June in 1987 and 1988. Recruitment failure of June sucker is not due to reproductive failure.     

Life cycle of the net-spinning caddisfly, Cheumatopsyche analis (Banks) (Trichoptera: Hydropsychidae), in two small Front Range urban streams, Fort Collins, Colorado

The life cycle of Cheumatopsyche analis (Banks) is described from 2 urban streams located in north central Colorado. Larvae were collected every 15 days during spring, summer, and fall and every 30 days in winter from August 1999 through August 2000. A total of 8652 larvae were collected, and head capsules were measured to the nearest 0.01 mm. The life cycle of C. analis at both sites appears to be partially bivoltine with a long, almost continuous period of recruitment after peak emergence in June. Some offspring from the early generation that emerges in May probably emerge as adults in September, while the remainder of the population overwinter as instars III through V. Life cycle patterns for C. analis in these 2 urban streams were most similar to other populations of Cheumatopsyche from Virginia.     

Reproduction by June sucker in a refuge population: successful spawning in a lake habitat

The June sucker ( Chasmistes liorus ) is an endangered lake sucker endemic to Utah Lake, Utah. As part of recovery actions, June suckers were introduced into Red Butte Reservoir, Utah, as a wild grow-out site. Since their introduction, June suckers have successfully reproduced in Red Butte Reservoir, producing a large population in this refuge. I used passive egg collectors (egg traps and nets) and observational surveys to determine the location of spawning sites within the reservoir, and larval light trapping to determine successful recruitment (i.e., egg survival through larval swim-up) at these sites. Eggs were collected between 18 June and 15 July at 2 general sites along or near the reservoir’s dam, although spawning was only observed at 1 of these sites. Suckers were not observed at, and eggs were not collected in or around, the mouth of Red Butte Creek as expected. At the site where spawning was observed, suckers were spawning over gravel substrates (mean diameter = 32 mm) at depths of 0.5–1.75 m. At the other site, suckers were spawning over silt/clay substrates (mean diameter < 1 mm) at depths of 1.1–4.75 m. Larval suckers were first captured along the dam where spawning was observed and eggs were captured, demonstrating that successful recruitment occurred at this spawning site. Larval suckers were never captured at the mouth of Red Butte Creek, confirming egg collecting data and observations that suckers did not utilize the stream for spawning. This June sucker refuge population is supported by lacustrine spawning, an important finding for management and recovery of this species.     

Larval growth rates and sexual differences of resource allocation in the cetoniine scarab Mecynorhina polyphemus Fabricius 1781 (Coleoptera: Scarabaeidae: Goliathini)

Larval ontogeny of the scarab Mecynorhina polyphemus was monitored throughout all instars, and larvae were weighed at 7-day intervals. Durations of the prepupal, pupal and postpupal stages were recorded. Larvae increase their body masses over 300 times during ontogeny. Male imagines are larger than females, and this is primarily a function of faster growth rates during instar III, resulting in significantly heavier larvae at the end of this instar. The durations of the three instars are not significantly different in males and females, but the duration of the prepupal and postpupal phases is significantly longer in males. There is a strong correlation in both sexes between maximal larval mass and the mass of the imago, but larval mass–imago mass scales with significantly different slopes in males and females. Male larvae must allocate increasingly more resources into production of cephalic horns with increments in larval mass, requiring differently proportioned pupal chambers.     

Intraspecific larval aggression in two species of Hyperini (Coleoptera: Curculionidae)

Two unusual types of behaviour (wandering and intraspecific aggressive behaviour) have been observed when rearing larvae of two species of the tribe Hyperini. Wandering of Hypera postica in search for food was observed in L1, L2 and L3 larvae, as well as in young L4 larvae. L1 larvae also disperse in response to crowding. Wandering of L2 to young L4 instars was a response to food shortage. Wandering of late L4 larva (‘prepupa’) occurs because of searching for a place to spin the cocoon and pupate. Encounters between the larvae may result in agonistic behaviour, and some larvae may die as a consequence of fighting. This aggression increases with food limitation. Agonistic intraspecific behaviour has not been described to date in weevil’s larvae and it probably may not occur under natural conditions when there is a plenty of food and larval densities are decreased by pathogens or parasitoids.     

Larval instars of the ant Strumigenys solifontis Brown (Hymenoptera: Formicidae): the fallacy of size distribution

Larval instars of the myrmicine ant Strumigenys solifontis Brown were determined by measuring the head width under a stereomicroscope and examining the morphology, especially chaetotaxy, by light microscopy and scanning electron microscopy. This study found that the larval stage consisted of four instars, but the first and second instars were not distinguishable by their head widths. However, the four instars could be discriminated clearly by a combination of size measurement and observations on the chaetotaxy. Within a population, there are few larvae in the first instar because of its short period (only 1–2 days before moulting into the second instar) and the low oviposition rate of the queen. Therefore, the first-instar larva needs to be collected separately from other instars so that it is not missed.     

Ontogenetic and habitat-related changes in diet of late larval and juvenile suckers (Catostomidae) in Upper Klamath Lake, Oregon

We describe ontogenetic patterns in the diets of shortnose and Lost River suckers (15.8–92.8 mm standard length) from Upper Klamath Lake in summer 1999. Both species made a transition from surface and planktonic prey to benthic prey at about 20–30 mm standard length, corresponding to the approximate size of the juvenile morphological transition. Surface prey was dominated by adult chironomids and undigestable pollen, while benthic prey was dominated by larval chironomids, chydorids, and ostracods. In the 15–20-mm size class, pollen made up >75% of food particles in 68% of specimens, and only 2 specimens in this size class lacked any pollen grains. A better understanding of the prey selection process in larval suckers is needed to determine the importance of this potential source of starvation. The planktonic prey eaten during the surface-to-benthic feeding transition were widely distributed in the lake, suggesting that larvae use emergent vegetation primarily as a refuge from predators. On a numerical basis, crustaceans and larval chironomids contributed most to the diets of larger juveniles. In specimens >40 mm, shortnose suckers ate more Tanytarsini and Lost River suckers ate more chironomid pupae and chydorids. In specimens >40 mm there was a strong habitat-related difference in diet: specimens collected in offshore samples ate more chironomid larvae and pupae, harpacticoid copepods, and chydorids, whereas onshore specimens ate more cyclopoid copepods and invertebrate eggs. The transition from onshore to offshore habitat appears to occur over a broad size range of about 40–90 mm.     

Life cycle and behaviour of Charoxus spinifer and Charoxus major (Coleoptera: Staphylinidae: Aleocharinae), predators of fig wasps (Hymenoptera: Agaonidae)

Charoxus spinifer is associated in southern Florida with native fig trees (Ficus aurea and Ficus citrifolia). Winged adult beetles, 3.0–3.6 mm long, mate on Ficus twigs outside the syconia (fruits), and enter the syconia through holes cut by male pollinating wasps. Adults and larvae eat adult wasps within the syconia. Ovaries hold few, large, mature eggs. Larvae develop through three instars. Fully grown larvae abandon the syconia, drop to the ground, burrow to a depth of 1.5–3.7 cm, spin a silken cocoon, and pupate. Pupal duration is 8–9 days. Larval populations are highest in May, when penultimate stage syconia (phase D) are most abundant, but were detected in all months except June. Charoxus major is reported from Veracruz, associated with Ficus lapathifolia. Its adults extract wasp occupants of galled fig ovaries within syconia, and its eggs were found singly in empty galls.     

Pherbina mediterranea: immature stages,biology, phenology and distribution (Diptera: Sciomyzidae)

The egg, three larval instars, and puparium of Pherbina mediterranea are described. The duration of the various immature stages indicates that this specis is univoltine and spends the winter as quiescent larvae. The biology, phenology and geographical distribution are presented. The main features of the larvae are illustrated with scanning electron micrographs. A key to the adults of genus Pherbina is given.     

Growth ‘rules’ and the larvae of decapod crustaceans

Summary

Statements that have attempted to express the relationship between the sizes of successive arthropodan instars are examined with reference to published data on larval decapod crustaceans.

The conclusions reached are (a) that ‘Brooks's Law’, which simply states that the lengths of successive instars form an exponential series, generally holds good in decapod larvae, (b) that ‘Przibram's Rule’, stating that the weight increase between instars is always by some power of 2, is not supported by the observed length changes, and (c) that Gurney's suggestion that growth factors in decapod larvae do not normally exceed about 1·5 is not applicable to the order as a whole, but may be valid for some sub-groups within it.     

Natural history of an ant–plant–butterfly interaction in a Neotropical savanna

Non-myrmecophilous lepidopteran larvae using plants bearing ant attractants such as extrafloral nectaries are good models for studying morphological and behavioural mechanisms against ant predation. Udranomia spitzi (Hesperiidae) is a butterfly whose larvae feed on leaves of Ouratea spectabilis (Ochnaceae), a plant with extrafloral nectaries. We described the early stages of U. spitzi, and used field observations and experiments to investigate the defensive strategies of caterpillars against predatory ants. Larvae pass through five instars and pupation occurs inside larval leaf shelters. Ant-exclusion experiments revealed that the presence of ants did not affect significantly caterpillar survival. Predation experiments showed that vulnerability to ant predation decreased with increase in larval size. The present study showed that predatory ants are not as relevant as demonstrated for other systems, and also illustrates how observational data and field experiments can contribute to a better understanding of the biology and ecology of a species of interest.     

Studies on Alenophalera bronneomixia (Lepidoptera: Notodontidae)—a pest of the West African indigo plant,Lonchocarpus cyanescens (Papilionaceae)

Summary

This paper is concerned with the general biology of the notodontid moth, A. bronneomixia whose larvae are found to be serious defoliators of the West African indigo plant, Lonchocarpus cyanescens.

At temperatures fluctuating between 21°C and 29°C (mean 22·5°C) and humidities between 70 to 95 per cent eggs developed and hatched in a mean of 11·1 days from deposition, mean hatch being 93 per cent.

Under the said environmental conditions, the life cycle from egg to adult entailed six larval instars and a prepupal stage before the real pupa, all lasting 60 to 80 days. Larvae were strongly monophagous, fed communally and in nature pupated in soil/litter very close to the foot of their invaded food plant.

Adults were retiring and in the field deposited clusters of numerous eggs preferably on the abaxial surfaces of their food plants. In nature, this moth's population seemed strongly regulated by high egg and larval parasitization, larval predation and fungal attacks at the pupal stage.     

Development of epipods and gills in some pagurids and brachyurans

Sepedon trichrooscelis is a semiaquatic, multivoltine species whose larvae feed on snails of the genus Succinea. The duration of the various developmental periods and larval biology are presented. The egg, three larval instars, and puparium of Sepedon trichrooscelis are described and illustrated. The distribution of the cuticular sensorial receptors, the shape of the hydrofuge setae on the posterior disc, and the details of the egg are illustrated by scanning electron micrographs.     

Bionomics and control of the walnut spanworm, Phigalia plumogeraria (Hulst), on bitterbrush in Utah

In 1979, the walnut spanworm defoliated a 1 ha bitterbrush seed orchard near Nephi, Utah. No seed was produced for two years thereafter due to feeding damage. Life stages were described and illustrated. The female is brachypterous and incapable of flight. First instar larvae readily drop on their silk threads and probably are dispersed by wind. The insect has one annual generation. Moths laid an average of 159 eggs per cluster in April; larvae began to appear in early May and matured by the first week of June. The pupal period extended from June until mid-April. The parasitic bombyliid, Villa faustina (Osten Sacken), was reared from pupae. In April 1980, shrubs contained an estimated average of 1044 eggs each. On 19 May, larvae averaged 1.9 per 7.5 cm of twig and were in the first and second instar. On 20 May the population was controlled by spraying with Sevimol-4. Other potential host plants, as determined from greenhouse tests, are rose, ceanothus, mountain mahogany, serviceberry, and willow.     

Size,spines and crochets: defences of luna moth caterpillars against predation by brown anoles

Field-testing predator-prey interactions between invasive exotic brown anole lizards and sentinel larvae of the luna moth, Actias luna, suggests that late instars of this saturniid, and perhaps many other saturniids, are well defended by their spines and crochets against predation by lizards. However, Actias luna larvae remain vulnerable to anole predation until they reach about 3 cm in length. In contrast, even relatively small caterpillars that are chemically defended, such as those of the io moth, Automeris io, and the monarch butterfly, Danaus plexippus, were shown to be well defended against anoles by their toxins. There is an obvious advantage for caterpillars to be chemically defended. However, there is also a tradeoff: Danaus plexippus are restricted to feeding on a relatively small group of plants, which limits resources and requires specialisation; in polyphagous Automeris io, the constant production of elaborate spines and toxin leads to prolonged larval development, which is at least twice as long as that of Actias luna, and exposes the caterpillars to mortality factors such as parasitism for a longer duration.     

The status of Hemilecanium imbricans (Green) (Homoptera : Coccoidea) in Africa south of the Sahara

Summary

This paper describes the findings from two series of observations on variation in C. austropalpalis L. and R. In Series I the distribution of head capsule lengths of 174 larvae, collected from 11 breeding sites in S.E. Queensland, was polymodal. Polymodality was also shown by the wing lengths of 15♂, 27♀ reared from 7 of the sites. In Series II the head lengths of 302 larvae from 5 sites (one not in Series I) gave the same polymodality, interpreted as representing 3rd and 4th instars of two forms A (smaller) and B (larger). 276 of these larvae, grouped on head length, were reared on agar and small nematodes, producing 62♂, 70♀ C. austropalpalis and 13♂, 5♀ C. narrabeenensis. The latter was not the cause of the polymodality. Adult wing lengths were bimodal in each sex. Form B was longer winged than form A. Within each form there was no significant correlation between larval head length and adult wing length. Only one of the many additional characters (19 in ♀; 22 in ♂) examined, differed between the two forms. Form B had more distinctly patterned wings with the intercalary pale spot more obvious. The results are discussed.     

Bionomics,behaviour and immature stages of Pelecotoma fennica (Paykull) (Coleoptera: Rhipiphoridae)

Ptilinus fuscus (Anobiidae) was confirmed as the host species of Pelecotoma fennica (Rhipiphoridae, Pelecotominae). Females of Pelecotoma oviposit into the wood infested by the host larvae. First-instar larvae are elongate, unsclerotized, very different from the triungulinid larvae known in other rhipiphorids. They search actively for the host larvae in the wood; no phoresy is involved in the life cycle. The first-instar larvae temporarily paralyse the host larva and enter its body, overwintering (some perhaps more than once) as an endoparasite. In the spring of the year of emergence, the endoparasite engorges enormously (without moulting) and develops a special sclerotized caudal structure which is then used for perforation of the host's integument. The larva undergoes a further four ectoparasitic instars. The fifth (i.e. fourth ectoparasitic) instar differs considerably from the preceding three, and is capable of boring through the wood to prepare the emergence gallery for the adult. Pupation occurs in the wood. The rate of parasitization may locally far exceed 50%. Superparasitization by the first-instar larvae is possible, but usually only 1 larva survives to the ectoparasitic stage. Larval morphology of Pelecotoma is described and illustrated. Additional data on bionomics and larval morphology are also presented for the genus Metoecus (Rhipiphorinae). Comparing the biology and larval morphology of Pelecotoma with other Rhipiphoridae, it is assumed that ancestral rhipiphorids may have been xylophilous Tenebrionoidea with predaceous or omnivorous larvae, and that the ‘triungulinid’ larvae and phoretic habits may not belong to the groundplan of the family Rhipiphoridae. The widespread opinion considering Rhipiphoridae closely related to the family Mordellidae is questioned.