Gerald T. Baker

Sensory cues and receptors for oviposition by Heliothis virescens

When given a choice of cotton (host) and ground cherry (non host) in a close range situation, Heliothis virescens (F.), the tobacco budworm, depends primarily on contact chemoreception and mechanoreception, and not olfaction or vision, to discriminate between these two plant species for oviposition. Further, in the presence of a certain level of hairiness (the non‐host plant, ground cherry, has short capitate hairs), the females are capable of discriminating between these two plants based on contact chemosensory cues, if at least one pair of tarsi is intact. The contact chemosensilla on the ovipositor do not seem to be important for this purpose. These results are discussed in relation to the sensory cues and receptors for oviposition in other Lepidoptera, especially moths.

Morphology and distribution of antennal sensilla of the tarnished plant bug, Lygus lineolaris (Palisot de beauvois) (Hemiptera: Miridae)

Abstract Sensilla on the antennae of adult and last-instar nymphs of the tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), were examined with light, scanning and transmission electron microscopy. Six different types were identified in adult females and males and 5 types in last-instar nymphs: types 1 and 4 are sensilla trichodea, 2 and 3 are sensilla chaetica, and 5 and 6 are sensilla basiconica. Type 1 are located at distal region of terminal segment and type 2 are located at distal regions of proximal 3 segments in both adults and nymphs. Type 3 is present on all segments, more numerous on scape and pedicel and less abundant on distal third and fourth segments in both adult and nymphal stages. Types 4 and 6 are absent on the scape and present on the distal 3 antennal segments in adults, but they are present only on the distal-most antennal segment in nymphs. Type 5 sensilla are present only on second antennal segments in adults and are absent in nymphs. Sexual dimorphism is observed in total numbers: there are significantly more type(s) 3, 4, 5 and 6 sensilla in adult males than adult females. Types 1, 4 and 5 are multiporous with thin cuticle, branched dendrites and pore tubules which suggests an olfactory function. These sensilla have 3, 3 and 2 neurons, respectively. The type 6 sensillum has an apical pore and pores in the cuticular wall, and is innervated by 5 nerve cells with unbranched dendrites. Sensillar types 2 and 3 have thick cuticle, a single apical pore and nerve cells with unbranched dendrites. Type 2 has 1 neuron and type 3 has 2 chambers and 2 nerve cells.

Sensory receptors on the larval maxillae and labia of Heliothis zea (Boddie) and Heliothis virescens (F.) (Lepidoptera : Noctuidae)

Abstract The maxillary and labial sensory receptors of the first-to-last instar larvae of Heliothis virescens and H. zea (Lepidoptera : Noctuidae) are described. The distribution, morphology, and number of sensilla on these mouthparts remain constant from instar to instar in both species. Several distinct differences in the morphology and number of certain sensory receptors (e.g. styloconic, digitiform, and multiporous plate sensilla) exist between H. virescens and H. zea . The sensory receptors on the maxillae and labium of both species are compared with those of other lepidopterous larvae.

Biology and life table of the cassava mite, Tetranychus truncatus Ehara (Acari: Tetranychidae)

Abstract The life history and life table of Tetranychus truncatus Ehara onmulberry leaflets were studied under laboratory conditions at 20, 24, 28, 31 and 35°C. Mites completed their development and produced offspring within this temperature range. The development time from egg to adult varied from 6.30 to 14.89 days. The highest immature mortality was 39.88%at 20°C followed by 30.70%at 35°C. The threshold temperatures of egg, larva, protonymph, deutonymph, and a generation were 11.38, 9.91, 10.67, 12.51 and 11.57°C whereas the day-degree requirement at each stage was 62.52, 15.38, 11.36, 11.76 and 142.83 Do, respectively. The highest number of eggs laid by fertilized females was 65.6 eggs at 24°C, followed by 64.78 eggs at 31°C. Fertilized females lived up to 28.41 days at 20°C and only 9.63 days at 35°C. Unfertilized females survived relatively longer at 24°C and produced slightly more eggs at 24 and 28°C. The net reproductive rate (Ro) was the highest (37.39) at 24°C, followed by 37.00 at 31°C. The innate capacity for increase (rm) and finite rate of increase (λ) reached maximal values (0.321 and 1.378) at 31°C, whereas minimal values (0.134 and 1.143) were at 20°C. The mean generation time was the shortest at 35°C and the shortest time for a population to double was 2.16 days at 31°C. The highest population trend index (49.49) was obtained at 24°C, followed by 48.58 at 31°C. The overall results suggested that T. truncatus could develop and reproduce within a wide range of temperatures. The range 24–31°C was the most suitable for the development, survival rate and reproduction of this mite.

Chemoreception in four species of water mites (Acari: Hydrachnida): behavioural and morphological evidence

Silver nitrate staining of the solenidial and eupathidial sensilla on the palpi, tarsi and tibiae of legs I and II of Arrenurus acutus, Geayia ovata, Mideopsis reelfootensis and Albia caerulea, along with ultrastructural studies, showed that these setae have a porous shaft cuticle. These setae are hollow and contain dendrites in their lumens and more than one neuron is associated with each setae. Behavioural experiments supported the involvement of these sensilla in the perception of chemical cues from prey and sexual partners.

Biological aspects of the geranium mites,Coptophylla caroliniani andAceria mississippiensis (Prostigmata: Eriophyidae)

Aceria mississippiensis andCoptophylla caroliniani (Prostigmata: Eriophyidiae) were found on wild geranium,Geranium carolinianum L., in northern Mississippi. About onehalf of the total developmental time was spent in the egg stage for each species. The developmental threshold forA. mississippiensis was 5.5±1.04°C and 7.3±0.93°C forC. caroliniani. The optimum temperature for each developmental stage was between 25 and 29°C.C. caroliniani failed to develop at 36°C, whereasA. mississippiensis failed at 40°C. Day-degree requirements to complete development were 100.7±3.6 Do and 154.6±4.1 Do forC. caroliniani andA. mississippiensis, respectively.Mean female longevity at 20°C was 17.4 (range 12–21) days forC. caroliniani and 16.5 (range 15–19) days forA. mississippiensis. The shortest pre-oviposition period was 2.2 days forC. caroliniani at 20°C and 1.7 days forA. mississippiensis at 25°C, and the length of pre-oviposition period increased with temperature above 25°C for both species.Maximum egg production ofC. caroliniani andA. mississippiensis occurred at 20°C. There were no differences (P≤0.05) in number of eggs per day at temperatures of 20, 25 and 32°C for each species, but there was a tendency to lay more eggs per day with increasing temperature. The percentages of egg hatch were not significantly different at these temperatures. The sex ratio of laboratory-rearedA. mississippiensis was 1:1.8, whereas field-collectedC. caroliniani showed a ratio of 1:1.

Sensilla on the mouthparts and antennae of the elephant louse, Haematomyzus elephantis piaget (Phthiraptera : haematomyzidae)

The labial palpus of the elephant louse Haematomyzus elephantis has six sensilla that represent three different types: trichoid, basiconic, and styloconic. Two rows of basiconic sensilla are situated on the dorsal and ventral surfaces of the rostrum, and each row consists of three sensilla. Male and female antennae have 15–17 trichoid sensilla situated on the scape, pedicel, and three antennal annuli. Both sexes have two sensilla basiconica on the dorsal surface of the pedicel near the junction of the scape and pedicel. Two coeloconic (tuft) sensilla are situated on the antennae of both sexes, one sensillum on each of the last two annuli. There are three plate organs, two on the last annulus and one on the penultimate annulus of the male and female antennae. Sexual dimorphism is exhibited in the male and female antennae, in that the male has about twice as many sensilla basiconica on the apex of the last annulus as does the female. The total number of sensilla basiconica on the apex of the male antennae is at least two times the number that is known to be present in any other species of lice.

Labial tip sensilla of Blissus leucopterus leucopterus (Hemiptera: Blissidae): Ultrastructure and behavior

The cuticular sensory receptors that are found on the apex of the labium of hemipterans play an important role in their feeding behavior. In this study we describe the ultrastructure, number, and distribution of sensilla on the labium apex of the chinch bug, Blissus leucopterus leucopterus. Each apical field of sensilla on the labium contains 11 uniporous peg sensilla and one sensillum chaeticum. The uniporous peg sensilla are innervated by 4–5 bipolar neurons that send dendrites in the lumen of each peg. Three neurons are associated with each sensillum chaeticum, two neurons have dendrites in the lumen of the sensillum, and the third dendrite ends in a tubular body at the base of the sensillum. Behavioral tests that involve chemical blockage of the sensory receptors show the importance of the labial sensilla in feeding behavior. Both morphological and behavioral evidence indicate that the labial sensilla have a chemosensitive function.

Sensory receptors on the adult labial and maxillary palpi and galea of Cicindela sexguttata (Coleoptera: Cicindelidae)

Five types of sensilla are situated on the apical area of the labial and maxillary palpi and galea of Cicidela sexguttata. Large, conical, and peg‐like sensilla are in rows on the central region of each palpus. These sensilla have a hollow cuticular peg, with an apical pore and multi‐innervation. This central region of palpal sensilla is surrounded by campaniform sensilla that are disc‐shaped and small conical peg sensilla. A similar type of conical sensillum as the found in the palpal central region is situated around the periphery of the palpal apex and apex of the galea. This conical peg sensillum is located in a shallow depression and is structurally similar to the other peg sensilla, but it has a mechanoreceptor neuron attached to the cuticular base of the sensillum. A long, single, trichoid sensillum is situated in the center of the galea and is hollow, thick‐walled, porous, and multi‐innervated. The apices of the palpi and galea have a large number of dermal gland openings that actively secrete a substance during the feeding process of the tiger beetle.

Morphological aspects of the third instar larva of Haematobia irritans

Abstract. The main morphological features of the cephalic region of the larva of Haematobia irritans (L.) are the oral grooves, tripartite labium and the antennomaxillary protuberances that have the dorsal, terminal and ventral sensory organs. The total number of sensilla that are found on the terminal organ differs from other cyclorrhaphous‐fly larvae. The fan‐shaped anterior spiracles usually consist of seven bulbous digits that are unequal in length. The creeping welts consist of notched, convex plates that split into two separate plates as they approach the midline of the venter. This characteristic has not been described previously for this species or other, higher, dipterous larvae. There are two posterior spiracles with an ecdysial scar, four fan‐shaped and branching spiracular hairs and irregularly‐shaped spiracular openings. The longitudinal anal opening is situated in the cuticular band that is known as the anal organ.