Head Width Measurements Research Articles

The evolution of body size in termites.

Termites are social cockroaches. Because non-termite cockroaches are larger than basal termite lineages, which themselves include large termite species, it has been proposed that termites experienced a unidirectional body size reduction since they evolved eusociality. However, the validity of this hypothesis remains untested in a phylogenetic framework. Here, we reconstructed termite body size evolution using head width measurements of 1638 modern and fossil termite species. We found that the unidirectional body size reduction model was only supported by analyses excluding fossil species. Analyses including fossil species suggested that body size diversified along with speciation events and estimated that the size of the common ancestor of modern termites was comparable to that of modern species. Our analyses further revealed that body size variability among species, but not body size reduction, is associated with features attributed to advanced termite societies. Our results suggest that miniaturization took place at the origin of termites, while subsequent complexification of termite societies did not lead to further body size reduction.

Life history characteristics of a cave isopod (Mesoniscusgraniger Friv.).

The special environmental conditions of caves provide habitat for several endemic and relict species, among them terrestrial isopods. The Baradla Cave system (north-eastern Hungary) hosts Mesoniscusgraniger (Frivaldszky, 1865) (Oniscidea, Microcheta, Mesoniscidae), a pygmy, blind, fragile troglophile woodlice species. Its stable environment can be characterised by the lack of light, high relative humidity (96%), low and constant temperature (about 10 °C). We explored the population characteristics (sex ratio, size distribution) and life history traits of the species (e.g. longevity, reproductive strategy, offspring number, and size). Sex ratio and size distribution of the individuals (head-width measurements) were estimated based on a yearly pooled pitfall-trap data set (N = 677). We studied the species’ reproductive strategy under natural conditions (Baradla Cave, Aggtelek National Park). Model populations were set up in the cave and checked monthly between March and October, 2016 (15 replicates, each with 12 randomly chosen adult individuals; ΣN = 180). Digital photos were taken of the live animals and their length was estimated based on the photos by using ImageJ software (average body length: 6.56 ± 0.79 mm). The results showed female dominance in the population [(male:female = 0.43:0.57); p < 0.001 (GLM)]. Female head width (0.87 ± 0.18 mm) was significantly greater than that of males [0.79 ± 0.08 mm; p < 0.001 (t-test)]. Based on our present data we assume that the offspring number per single female is low (3–5), and new-borns have a relatively large size (body length: 4.22 ± 0.53 mm) compared to the adults. The probability of reproduction was continuous by monthly intervals (binomial test) and longevity exceeds one year. Our results suggest that the species follows a stenodynamic life history.

A new South American species of Banasa Stål (Hemiptera: Heteroptera: Pentatomidae: Pentatominae): from egg to adult

Banasa maculata sp. nov. is described from a Brazilian Atlantic Forest, including immature stages and aspects of its life history. Adults and nymphs were reared in laboratory and fed on fruits of Miconia sellowiana (Melastomataceae). Eggs and first instars of B. maculata are similar to those of other species of Banasa; however, the color pattern of the abdomen distinguishes B. maculata, particularly first, fourth, and fifth instars. Light and dark morphs were observed for third, fourth, and fifth instars. Head-width measurements overlap only between fourth and fifth instars. Eggs of B. maculata, in S.E.M., show a reticulate pattern with deep cells and irregular rims. The most frequent size of an egg clutch was 12. Average duration of the immature stages (egg to adult) was 37.6 ± 13.24 days. The highest mortality occurred in the fifth instar (45.9%). Banasa maculata belongs to the “cuspidata group” of Banasa because of the presence of an apical projection of each posterolateral angle of the pygophore. Adults of B. maculata resemble B. varians Stål; the new species is recognized by the transversal, irregular, broad macula on pronotum; gonocoxites 8 deeply excavated medially; and the male proctiger subtriangular, narrowing toward the apex.

Characterization of age and cuticular hydrocarbon variation in mating pairs of house fly, Musca domestica, collected in the field

House flies, Musca domestica L., were collected in copula over two summers from six dairies located in three climatically distinct regions in the U.S.A. southern California, Minnesota and Georgia. Ages of males and females from a total of 511 mating pairs were estimated using pterin analysis. Cuticular hydrocarbon profiles and gonotrophic ages of females also were evaluated. Mean age of mating males ranged from 54 to 102 degree-days (DD) (4-10 days based on field air temperatures), depending on the farm. Very young males (< 10-20 DD) and old males (> 200 DD) were rare in mating pairs. Mean female age at mating ranged from 20 to 46 DD (2.5-4 days). All mating females had eggs in the early stages of vitellogenesis and 99.2% were nulliparous. However, some older and parous females were collected, demonstrating that re-mating can occur in the field. Head width measurements of mating pairs suggested that assortative mating by size did not occur. The cuticular hydrocarbon profiles of females were determined, with emphasis on (Z)-9-tricosene (muscalure). Overall, only 55% of mating females had detectable amounts (> 4 etag per fly) of (Z)-9-tricosene. Of the females that had detectable (Z)-9-tricosene, variation in amount per female was high in all fly populations, and thus was not statistically related to the size or age of the mating female. The proportion of mating females with detectable levels of (Z)-9-tricosene varied by geographic region. Seventy-one, 63, and 27% of females from southern California, Minnesota and Georgia had detectable amounts of (Z)-9-tricosene. Principal components analysis of the eight most abundant hydrocarbons from mating females, by state, revealed state-level distinctiveness of hydrocarbons in house fly populations, which may reflect genetic variation associated with environmental stresses in those geographical zones.

Determination of Paronychiurus kimi (Collembola: Onychiuridae) age structures by head width measurements with reference to cadmium toxicity

The age structure of Paronychiurus kimi (Lee) was determined by analysis of the head capsule width distribution using a H CAP program. The H CAP program successfully separated five distinct peaks, which represented a single age group, with a low misclassification probability of 0.1. The mean head capsule widths for each age group were 0.123, 0.165, 0.258, 0.304 and 0.350 mm, respectively. The age groups of P. kimi could be subdivided into two postembryonic developmental stages, the juvenile stage (groups 1 and 2) and adult stage (groups 3–5), on the basis of stage at first reproduction of P. kimi. Based on this information, we examined the chronic effect of cadmium on the age structure of P. kimi. After 28-day chronic exposure to various cadmium concentrations, the total number of P. kimi individuals decreased in a concentration dependent manner. The proportions of the juvenile and adult stages to the total number of individuals in the cadmium treated soils were significantly different from those in the control. In addition, the overall proportions of age structures were affected by cadmium treatment. These results indicate that head capsule measurements can be used to determine the age group of P. kimi and chronic exposure of cadmium to P. kimi at the individual level may be translated and manifested at the population level, by changing the age structures of P. kimi populations.

Morphology of the immatures and biology of Chinavia longicorialis (Breddin) (Hemiptera: Pentatomidae)

Chinavia longicorialis (Breddin) is recorded only in Brazil, Argentina and Uruguay on host plants of at least three different families. Adults and nymphs were reared under standard controlled conditions (24 +/- 1 degrees C; 70 +/- 10% RH; 12hL:12hD), and fed on green beans (Phaseolus vulgaris L.). Eggs and first instars of C. longicorialis are very similar to those of other species of Chinavia; however, the presence of orange maculae at the thoracic pleura is exclusive of first instars of C. longicorialis. Third to fifth instars have abdominal maculae divided by pseudo-sutures, a diagnostic feature of C. longicorialis nymphs. Light and dark morphs were observed for third, fourth and fifth instars. Head width measurements did not overlap between consecutive instars. The most frequent size of an egg clutch was 14; we suggest the adoption of the mode as the best and useful estimate of the egg clutch size for Pentatomidae. Average duration of the immature stages (egg to adult) was 39.4 +/- 3.20 days. The high mortality observed from second to fifth instar (82.4%) and the lack of reproduction of the second generation indicate that green beans are unsuitable to proper development and reproduction of C. longicorialis by itself.

Mating Behavior, Male Territoriality and Chemical Communication in the European Spiral-Horned Bees, Systropha Planidens and S. curvicornis (Hymenoptera: Halictidae)

Male behavior and the significance of odor signals in mate-seeking were investigated in the spiral-horned bees Systropha planidens and S. curvicornis. In both species the females are oligolectic on the bindweed Convolvulus. Males held territories containing Convolvulus flowers, suggestive of resource defense polygyny. They patrolled fixed routes over flower patches and defended them against other males. In physical combat, grappling males struck each other repeatedly with the sharp-edged apex of their metasoma employing the conspicuously enlarged eighth sternum as a ram. Head width measurements showed that males in both species are larger than conspecific females. Most copulations occurred in Convolvulus flowers. Behavioral experiments with scented bee dummies revealed evidence for odor-cues in mate recognition. It is probable that long-range visual signals are used to locate competitors and mates on flowers, whereas at close range, chemicals presumably on the cuticle surface are responsible for sex and species recognition.

Physical worker castes in colonies of an acacia-ant ( Crematogaster nigriceps ) correlated with an intra-colonial division of defensive behaviour

Crematogaster nigriceps (Emery) is one of the acacia-ants inhabiting the swollen thorns of Acacia drepanolobium trees in East Africa. The ants show two distinctive behaviours in response to being disturbed. Some ants (“Defenders”) readily leave the swollen thorns to defend the tree, whilst others (“Domestics”) remain inside the swollen thorns and will not move unless provoked into doing so. Analysis of head length and head width measurements of the ants shows conclusively that the two behavioural castes are also physical castes. Defenders have significantly larger heads (Head length 0.97 mm ± 0.006, Head width 0.98 mm ± 0.006) than the Domestics (Head length 0.78 mm ± 0.008, Head width 0.81 mm ± 0.007). It is concluded that there is an intra-colonial division of defensive behaviour within the worker ants of C. nigriceps, mirrored by a physical sub-division of the worker caste.

Separation of Cat Flea (Siphonaptera: Pulicidae) Instars by Individual Rearing and Head Width Measurements

Two methods to verify whether head width measurements fit Dyar's rule were evaluated for the separation of instars of the cat flea, Ctenocephalides felis (Bouché). Individual rearing was a reliable method of determining larval instar but was labor-intensive. The mean observed head widths were significantly different for each instar (first instar, 0.164 mm; second instar, 0.201 mm; third instar, 0.260 mm) and showed no sexual dimorphism. Head capsule width increased roughly 25% from instar to instar with geometrically progressing growth in accordance with Dyar's rule. However, head capsule width cannot be used to determine the instar of randomly selected larvae because the measurements overlap broadly between instars.

The tropical bedbug Cimex hemipterus near the southernmost extent of its range

The average degree of infestation of Cimex hemipterus in Zulu huts in South Africa is the same as that of C. lectularius. Nymphal stages of C. hemipterus can be distinguished by head-width measurements and numbers of lateral pronotal hairs.

Host Parasitism and Progeny Production of Two Strains of the Parasitoid Nasonia vitripennis (Hymenoptera: Pteromalidae) on the House Fly (Diptera: Muscidae)

Host parasitism and progeny production were determined for two strains of the parasitic wasp, Nasonia vitripennis (Walker), reared on house fly, Musca domestica L., hosts. One strain (NY) was collected in New York State and has been reared in the laboratory for ca. 2 years while the other strain (MA) was originally collected in Woods Hole, Mass., and maintained in the laboratory for 30 years. NY females parasitized >2-fold as many hosts and produced nearly 2-fold as many progeny as MA females. In addition, adult longevity of NY was significantly longer than that of MA. Size of the females, determined by head width measurements, did not differ between the two strains. Differences between the two strains appear to be due either to intrinsic population differences (since each strain was collected in a geographically different region) or to the effects of long-term rearing on the MA strain, or both. Information obtained from this study suggests that NY would probably be more effective as a biological control agent than MA.

The Influence of Size on Foraging in the Ant, Atta cephalotes, and the Effect of Some Plant Defence Mechanisms

SUMMARY (1) Headwidth measurements of Atta cephalotes workers showed that the population size structure was continuously variable, unimodal and heavily skewed towards the smaller individuals with a peak at a headwidth of 0-7-0-8 mm. (2) The largest workers (soldiers) and smallest workers are less frequent on foraging trails from which the size frequency is also skewed towards smaller individuals and peaks at a headwidth of 1 1-1 4 mm. (3) The size range of foragers carrying leaf-burdens was found to be from 2-0-4-8 mm headwidth with a peak at 2 9-3 0 mm. (4) Small workers ('hitch-hikers') being carried to the nest on leaf fragments were found to range from 0.8-2.1 mm in headwidth with a peak at 1-3-1-4 mm. (5) Moisture contents of foraging workers were found to be significantly higher in returning than outgoing individuals in all size classes indicating that liquids as well as vegetable material are collected. (6) Using plants labelled with the radioisotope 32P it was established that foragers drink the sap exuded from the cut edges of leaves. (7) Plant species containing latex systems were found to be significantly less attacked than species without. (8) The role of sap collection and plant secondary compounds in attine foraging behaviour is discussed.

OBSERVATIONS ON THE BIONOMICS OF THE DARK-SIDED CUTWORM, EUXOA MESSORIA (LEPIDOPTERA: NOCTUIDAE), IN ONTARIO

AbstractThe dark-sided cutworm, Euxoa messoria (Harris), has a North American distribution and is commonly found in tobacco fields in Ontario. It has one generation a year, and overwinters as an egg in the soil. Hatching takes place in early April and the young larvae feed on the rye rotation crop; later they attack newly transplanted tobacco seedlings. Head width measurements of larvae collected from the field show seven instars, but individual rearing data of E. messoria larvae reveal that small numbers pass through six and an occasional larva passes through eight; however, the eighth instar has the same head width as the seventh. Pupation occurs from late July to mid-August in the soil. The adult emerges from mid-August to October, and oviposition occurs in this same period. Eggs are completely developed before winter. Behaviour and duration of the different stages are described. Natural mortality factors of the species are given.

Life History of the Looper Phigalia titea1 in Virginia2

The half-wing geometer, Phigalia titea Cramer, is an obscure hardwood defoliator occurring in the eastern half of the United States. An outbreak in the mountains of northwestern Virginia provided an opportunity to obtain information on the life history and natural enemies of this insect. P. titea has 1 generation a year. The insect overwinters as a pupa in the soil. Adult emergence occurs from late March to mid-April, and oviposition occurs in this same period. Hatching takes place in late April and the larvae feed for approximately 1½ months. Head-width measurements and individual rearing data of P. titea larvae reveal that this species progresses through 5 instars during larval development. Pupation occurs in late May and early June in the litter near the soil surface. Descriptions of the immature stages are given. The following parasites were recovered: Telenomus alsophilae Viereck, Apantales palcacritae Riley, A. murtfeldtae Ashmead, Hypopteromalus tabacum Fitch, Pimplopterus sp., and Tachinomyia sp. Several of these are new host records.