Influence of the holly leaf miner,Phytomyza ilicis (Diptera Agromyzidae), on leaf abscission

Holly trees were sampled at two heights for 11 annual generations of Phytomyza ilicis Curtis. The number of mines per 1000 leaves, mine intensity, was consistently more at the lower height. Mine-induced leaf abscission led to a reduction in mine intensity from 1- to 2-year-old leaves. Abscission was shown to have been greater in samples taken from higher in the tree. There was a suggestion of a density-dependent effect on the probability of mine-induced abscission.     

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.     

Laboratory studies on the effect of crowding on phase and the life history of Schistocerca pallens (Thunberg) (Orthoptera: Acrididae: Cyrtacanthacridinae)

Summary

The life-history of Schistocerca pallens (Thunberg) has been studied under controlled laboratory conditions.

Both isolated and crowded stocks passed through six nymphal instars, with which the number of eye-stripes in the compound eye correspond.

The mean length of nymphal life of isolated individuals was 64·8 days for males and 67·1 days for females. Mean duration of nymphal life of individuals reared in crowds was 60·1 days irrespective of sex.

The mean time elapsing between the last ecdysis and the first oviposition for isolated females was 32·8 days. Each female laid an average of 6·36 egg-pods with an average of 57·8 days. Each female laid an average of 6·36 egg-pods with an average of 57·8 eggs por pod; of these 63·3% hatched.

Crowded females laid their first egg-pod on the seventeenth day. They laid an average of 14·44 egg-pods per female with a mean of 60·70 eggs per pod, of which 77·58% hatched. There was no significant difference in fecundity between females grown at the two rearing densities, but there was a great difference in fertility.

There was no difference in hatchling weight between the two rearing densities.

No significant chromatic or behavioural variations occurred in relation to isolation or crowding, but morphometrics showed differences associated with rearing density.     

Nasal botflies of migrating wildebeest from western Zambia

Summary

A migratory population of wildebeest (Connochaetes taurinus) in Liuwa Plain National Park in the Western Province of Zambia was sampled for nasal bots (Diptera: Oestridae: Oestrinae) during 1975–78. Infestations from 32 antelope included Gedoelstia spp. (two species), Oestrus aureoargentatus and O. variolosus. A total of 1913 second and third instar larvae was recorded from the sinuses and nasal septa with individual parasite loads varying from 4 to 144 bots. No obvious pathogenicity was attributable to these oestrids, all four species of which were judged to be multivoltine in this habitat. The significance of this voltinism in relation to the migratory course of the wildebeest is discussed together with a consideration of parasite densities and the potential threat of myiasis to domestic livestock in the area.     

A new species of Melanagromyza (Diptera: Agromyzidae) mining leaves of Bromelia pinguin (Bromeliaceae) in a dry forest in Costa Rica

Melanagromyza rosales, sp. nov., from Costa Rica is described and its natural history is summarized. Larvae are miners in leaves of Bromelia pinguin, a large terrestrial rosette plant. They form conspicuous longitudinal mines that may be over 1 m long. Adult emergence is virtually simultaneous for all individuals, probably triggered by temperature cues. Populations are low for many generations with brief periods of abundance.     

Morphology and feeding behaviour of the leaf-mining larva of Cheilosia semifasciata (Diptera: Syrphidae)

In North Wales the larva of Cheilosia semifasciata (Diptera: Syrphidae) makes full-depth blotch mines in leaves of Umbilicus rupestris. Mines occur mostly on shaded plants with one larva per plant. Each larva mines several leaves to complete development and initiates new mines by curling round the leaf margin and puncturing the epidermis under the leaf. Unlike other dipteran leaf-miners which feed on their sides, only the thorax is turned sideways when feeding. The larva uses a grasping organ on the anal segment to grip the substrate when moving externally on the food-plant. Inside leaf mines, position is further secured by the integumental vestiture which grips the epidermis above the larva. The morphology and behaviour of the larva of C. semifasciata differs markedly from larvae of three congeneric species that tunnel in stems and roots.     

Decapod Crustacea from the International Indian Ocean Expedition (Larval and post-larval stages of Parapenaeus Smith (Penaeinae)

Summary

Developmental stages of Parapenaeus investigatoris Alcock and Anderson from second protozoea to late post-larva and an incomplete series of P. longipes Alcock and P. fissurus (Bate) are described and figured. Important generic characters of the larvae of Parpaenaeus are two pairs of supra-orbital spines in the protozoeae, a strong hepatic spine, a long dorsomedian spine on the third abdominal segment, ventromedian spines on the anterior abdominal segments and sometimes on the last thoracic segment, a pair of dorsolateral spines on the fifth and sixth abdominal segments and a median spine on the telson.

The species recorded are widely distributed in the northern Indian Ocean, particularly in the Bay of Bengal, but only two specimens were taken south of the Equator and few in the more open parts of the ocean.     

LX.—Copepoda and Cladocera of the Cuillin Hills of the Isle of Skye

Summary

The life history of the African grasshopper Ornithacris turbida (Walker) was studied under controlled laboratory conditions. No phase variation was observed between isolated and crowded stock in respect of colour, morphometrics, weight of hatchlings or fledglings. All the females reared in isolation Had seven nymphal instars but in the case of the isolated males the majority had six but some had seven nymphal instars. This variation was also observed in the crowded stock for both males and females.

In isolation the mean nymphal life of 15 females was 78·7 ± 3·2 days, the mean for nine males having six instars was 59·9 ± 3·2 days and for five males having seven instars the mean nymphal life was 74·6 ± 3·8 days. Overall the nymphal life for the insects reared in crowds was slightly shorter, but no attempt was made to separate the insects having six or seven instars.

The stripes in the compound eye correlated with the number of nymphal instars. Colour changes in the compound eye coincided with overall body colour changes and maturation.

The mean maturation period of females reared in isolation was 101 days, varying from 72 to 158 days. The mean maturation period of the crowded females, estimated by the collection of the first egg-pod, was 73 days with a range of 62 to 84 days; when estimated by the collection of egg-pods averaging one per female it varied with the cage from 91 to 114 days. This suggests that maturation in the crowded females was quicker.

The isolated females lived longer than ones reared in crowded conditions, and laid more egg-pods. There was, however, no difference in the number of eggs per pod or their hatchability between crowded and isolated stock. In both cases 76% of the total number of eggs hatched. Hence overall the isolated females had a greater fecundity than those reared in crowds.

The average weight of a single hopper from isolated parents was 15·5 mg and that from crowded parents was 14·0 mg.     

The parasites of the psyllidae—3. Some notes on the biology and host relationships of Parapsyllae-Phagus Adulticolus Robinson (Hymenoptera)

Abstract

Parapsyllaephagus Adulticolus Robinson (CHALCIDIDAE: Encyrtinae) is an endoparasite of the adults of Psylla melanoneura Förster and Psylla subferrigenea Edwards. The life histories and biology of the hosts and parasite are described. Parapsyllaephagus adulticolus has five larval instars, which feed selectively upon the developing internal genitalia of the host at first, and eventually, as the final instar, upon the whole of the abdominal viscera. Pupation within the psyllid is followed by emergence of the adult parasite through the posterior dorsal surface of the abdomen of the host. The effect of these activities upon the migration of the adult psyllid from a winter shelter plant to a summer host plant is discussed and a relationship between the stimulus to migrate and the state of development of the internal genitalia is postulated. Some aspects of the orientation of the parasite larva within the host and the phenomenon of larval reversal are discussed.     

The occurrence of an additional instar in the development of Chorthippus brunneus (Orthoptera: Gomphocerinae)

In two populations of Chorthippus brunneus in the Breckland district of East Anglia an additional instar is interposed between instars II and III during the development of female nymphs. The IIa nymph occurs with a frequency approaching 100%, in both heavily and very lightly grazed grasslands.

The IIa nymph is intermediate in morphological characteristics between the second and third instars. It is characterized by having wing buds similar to those of a second instar except with more extensive venation, while the genitalia are more like those of a third-instar nymph. The pronotum length: head length ratio is approximately 1·0 and there are 16 or more annuli in the antennae.

Members of the population taken from the very lightly grazed grassland and raised in the laboratory on grass that had been heavily grazed by rabbits omitted the IIa instar and so passed through only four stadia during their development. In contrast, members of the population taken from the heavily grazed field site continued to include the IIa instar in their development when fed in the laboratory on grazed grass.

Comparisons with other studies of this species show that there is geographical variation with respect to numbers of instars passed through during development. The additional instar has been found only in East Anglia where the warmer sunnier climate, which is semi-continental in the Breckland district, leads to earlier hatching. This allows more time for an extra instar to be included in the development.

The ecological implications of the observed variation in life history are discussed.     

The identity of Orius tantillus (Motschulsky) and notes on other Oriental Anthocoridae (Hemiptera,Heteroptera)

Abstract

Studies on the biology of Toxoptera aurantii (Boy.) showed that populations of the aphid contain females only, and that reproduction is parthenogenetic and viviparous and occurs exclusively on the undersurface of flush leaves. The aphid is described and a key is drawn for the various instars. The development of the aphid is temperature-dependent but at the optimum temperature it takes 6 days to become adult. The incidence of alates in populations is influenced both by high aphid density and leaf age.     

The parasites of the Psyllidae—2. Parapsyllae-Phagus Adulticolus gen. et sp. nov., the first Hymenopterous parasite of an adult psyllid (Homoptera)

Abstract

The first Hymenopterous parasite of adult psyllids, Parapsyllaephagus adulticolus gen. et sp. nov. (Chalcididae: Encyrtinae) is described from Psylla melanoneura Förster in the North-east of England. The parasite has also been obtained from Psylla subferrigenea Edwards. The new genus is characterised by a number of concurrent morphological structures, outstanding amongst which is the presence of a distinct poststigmal vein on the forewing, such that the stigmal vein leaves the submarginal vein some distance before the costal margin.     

Natural history of the terrestrial amphipod Cerrorchestia hyloraina Lindeman (Crustacea: Amphipoda; Talitridae) in a Costa Rican cloud forest

The field biology of the Costa Rican landhopper (Crustacea: Amphipoda: Talitridae) Cerrorchestia hyloraina Lindeman was investigated in the Monteverde Cloud Forest Reserve, Costa Rica. On the Pacific (leeward) side of the continental divide, local distribution follows a gradient of moisture, from densities of over 200 m^-2 in the elfin forest at 1600 m, to extremely low densities in drier forest types. Below 1400 m, the leaf litter is apparently too dry to support landhopper populations. On the Caribbean (windward) side of the continental divide, landhoppers occur well below 1400 m. A discussion of geographic distribution is included. Landhoppers prefer aged (microfaunally pre-processed) leaves as food, and move about only at night or in the mornings of heavily overcast days. Average female fecundity is seven eggs, with progressive loss of marsupium contents over time. The sex ratio is biased towards females. In cloud forest, breeding apparently is continuous throughout the year, with some increase after the beginning of the rainy season. There are 9–10 juvenile instars and 5–6 adult instars. The relationship of antennal segment number to total body length is linear.     

XXX.—Trichoptera collected in Morocco by Messrs. K. H. Chapman and G. A. Bisset

Summary

The tube-building amphipod Microdeutopus gryllotalpa Costa was successfully reared through several generations in the laboratory. Females produced young at six to eight day intervals, as many as eleven broods being produced during the two-month reproductive life of a single female in the laboratory. Brood numbers increased and decreased cyclically throughout the breeding period of any one female and a maximum of 58 young in a single brood was recorded. At 21°C young moulted at five-day intervals during their early instars and at about nine to ten day intervals in their later stages. Both sexes reached sexual maturity after the ninth moult, but males continued to differentiate morphologically after attaining sexual maturity.     

On the status of Arcitalitrus dorrieni (Crustacea: Amphipoda) on the island of Colonsay,Inner Hebrides

The presence of the landhopper Arcitalitrus dorrieni (Hunt) is reported on the island of Colonsay, Inner Hebrides. It is widely distributed there amongst deciduous leaf litter in forested areas but also occurs in bracken litter and scrub grassland. The species is an introduction from Australia, doubtless transported inadvertently among plants brought to the gardens at Colonsay House. It is, however, not restricted to the ornamental plantings but has colonized native woodland. Maximum population density recorded under leaf litter was 680 m². Amphipods avoid waterlogged or dry situations preferring to burrow in moist soil under litter from deciduous trees. Coniferous woodlands are more sparsely colonized. Rate of spread (minimum) from the original locus is calculated at c. 25 m/year. Arcitalitrus may prefer to eat sycamore leaves (cf. oak, beech). Ovigerous females are reported for May but no evidence exists for a release of young any earlier in the year. Immature amphipods seem to live more covert lives in the soil beneath the superficial litter layer. Eggs are relatively large and few in number. Amphipods may avoid ants but may have a mite living in phoretic or ectoparasitic association.     

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.     

A new species of Josephiella (Hymenoptera: Agaonidae) forming leaf galls on Ficus microcarpa L. (Moraceae)

A second species of Josephiella Narendran, J. microcarpae, is described and figured, based on specimens reared in Hawaii, California and the Canary Islands. This wasp develops in galls on the leaves of Ficus microcarpa L., a widely cultivated ornamental banyan tree that is native to South-East Asia and adjacent islands. It has not been found on any other hosts. Both sexes are described, and males, which are apparently all fully winged, are relatively rare. We postulate that this wasp is a recent introduction into Hawaii, California and the Canary Islands, from an unknown location in South-East Asia, where Ficus microcarpa is native.     

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.