Donald B. Thomas

Reproductive phenology of the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae) in the Sierra Madre Oriental, Northern Mexico

In its native habitat in northern Mexico, Anastrepha ludens (Loew) is normally bivoltine although a third generation is achieved in some years. The flies overwinter mainly in the puparial stage, emerging in January-February. These flies oviposit in the spring crop of a wild citrus, Sargentia greggii (S. Wats.). The primary population peak follows in late spring to early summer (in exceptional years, separate peaks in spring and summer). Dissection of the females demonstrated that most of the flies in the spring peak are reproductively immature, indicating emergence of new adults. Activity subsides in late summer, or at least, few flies can be trapped at this time. Then in the fall there is a resurgence of adult activity. However, in contrast to the spring peak, dissection revealed that the great majority of the fall adult females are already gravid, indicating that they are carry-overs from the early summer population, rather than new recruits. The fall adults oviposit in October-November, producing the overwintering population that will emerge as adults in January-February.

Post-blood meal analysis of Stomoxys calcitrans (L.) haemolymph for the presence of bovine immunoglobulin G

Abstract Pooled haemolymph samples collected from adult stable fly, Stomoxys calcitrans , following a blood meal, were analyzed for the presence of bovine immunoglobulin G. Western-blot analysis, utilizing anti-sera specific for bovine immunoglobulin G, with a demonstrated sensitivity of 1 ng/fly, failed to detect immunoglobulin G in the haemolymph. This finding does not rule out the possibility that subdetectable, but still biologically active, levels of immunoglobulin G enter the haemolymph. However, based on our estimates of the size of a blood meal and the amount of immunoglobulin G in bovine blood, we calculate that if it passes the gut wall into the haemocoel it is much less than 1% of the amount ingested. In contrast, small amounts of bovine serum albumin, a protein larger than immunoglobulin G subunits and fab or fc fragments, does pass into the haemolymph at detectable levels. This research has important implications from the standpoint of induced immunity to bloodsucking flies.

Nontoxic Antifreeze for Insect Traps

ABSTRACT Propylene glycol in water is a safe and effective alternative to ethylene glycol as a capture liquid in insect traps (pitfalls, flight intercepts, pan traps). Propylene glycol formulations are readily available because it is the primary (95%) ingredient in certain automotive antifreeze formulations. However, an even safer and less expensive alternative is the USP food grade RV antifreeze used for winterizing drinking water systems. The automotive formulations contain additives (about 5%) that contribute to the cost and involve safety, environmental, and waste disposal issues. Using bacterial inhibition as an indicator, the preservational attributes of the automotive and RV antifreeze were found to be comparable in laboratory tests. Entomologists are urged to use nontoxic antifreeze in their trapping programs.

SURVIVAL OF THE PUPAL STAGE OF THE SCREWWORM, COCHLIOMYIA HOMINIVORAX (COQUEREL) (DIPTERA: CALLIPHORIDAE) IN SUBTROPICAL MEXICO

Survival of the screwworm pupal stage was studied under different ecological conditions over a 12-month period in southern Mexico. Survival (measured as successful adult eclosion) differed only sli...

The Genus Eleodes Eschscholtz (Coleoptera: Tenebrionidae) in Texas

Abstract False wireworms are larvae of the darkling beetle genus Eleodes Eschscholtz, some of which are agricultural pests of dryland wheat. Because of the large number of species in the genus (approximately 235), identifications can be problematic. Hence, regional keys are of great utility. Within the state of Texas a total of 31 species are known to occur: E. acutus, E. arcuatus, E. carbonarius, E. caudiferus, E. debilis, E. delicatus, E. dissimilis, E. easterlai, E. extricatus, E. fusiformis, E. goryi, E. gracilis, E. hispilabris, E. knullorum, E. labialis, E. longicollis, E. mirabilis, E. neomexicanus, E. nigrinus, E. obscurus, E. opacus, E. pedinoides, E. spiculiferus, E. spinipes, E. sponsus, E. striolatus, E. suturalis, E. tenuipes, E. tricostatus, E. veterator, and E. wenzeli. Herein we provide a key with illustrations and a brief diagnosis for the adult of each Texas species, along with notes on ecology, distribution, and pest status.

Cattle fever tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae): Potential control on pastures by the application of urea fertilizer

The southern cattle fever tick, Rhipicephalus (Boophilus) microplus, spends as much as 80-90% of its life cycle as a larva questing for a host. Standard control methods are limited to on-host applications, leaving a need for methods directed at the pasture infesting stages. Reports from Brazil indicate that pasture fertilization can reduce tick numbers. Granular urea was tested using standard pesticide efficacy methods in both the laboratory and field trials to determine if there was a significant impact on adult reproduction and larval survival. Under the conditions of this present study, there was no detectable effect on either female adults or larval stages. Ammonification in the soil may be a key factor limiting the impact of fertilizer treatments.

Population Dynamics of Off-Host Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) Larvae in Response to Habitat and Seasonality in South Texas

The cattle tick, Rhipicephalus microplus (Canestrini), is an economically destructive arthropod because of its ability to vector bovine babesiosis. It is known that cattle ticks can spend 80–90% of their lifecycle as questing larvae, yet the effect of climatic factors on their off-host behavior and survival is unclear. The goal of this study was to measure the effects of specific ecological factors on off-host questing larvae in nature. The study was conducted in a south Texas pasture over a two-year period, during which time larval populations were surveyed. Simultaneously, weather variables—precipitation, relative humidity, and ambient temperatures—were recorded. Larval survival rates varied among seasons, with the overall highest populations recorded in the spring and the lowest in the fall by a ratio of 20:1. In the winter, the larger numbers were collected from exposed habitats at a ratio of 6:1. Conversely, canopied habitats in the summer had 10-fold larger larval numbers. In the spring, exposed and canopied habitats showed no difference in tick larval survival rates. The results show that the interaction between season and habitat strongly influence off-host questing tick survival. Relative humidity was a key weather variable.

TICK VECTOR AND DISEASE PATHOGEN SURVEILLANCE OF NILGAI ANTELOPE (BOSELAPHUS TRAGOCAMELUS) IN SOUTHEASTERN TEXAS, USA

Abstract Nilgai (Boselaphus tragocamelus) are nonnative bovines that were originally introduced as game animals to one large, south Texas, US ranch but that are now present throughout southeastern Texas from Baffin Bay to Harlingen and in northern Mexico at least as far west as Durango. Between October 2014 and January 2017, nilgai (n=517) were examined for the presence of tick ectoparasites, with particular interest in the cattle fever tick, Rhipicephalus (Boophilus) microplus. These animals were either hunter killed or they were culled as part of federal cooperative harvesting from Cameron and Willacy counties in southeastern Texas. The proportion of fever tick-infested animals differed in a N-to-S pattern, and this was at least partly attributed to differences in habitat. The southern area is a lowland floodplain predominated by halophytes, whereas the northerly area is upland thorn scrub, the latter of which provides a vegetative canopy that is more conducive to tick survival and persistence. A subset of nilgai, all from the Texas–Mexico border area, were screened for livestock pathogens using molecular and serological assays. All nilgai were seronegative for Babesia (Theileria) equi and Babesia cabalii. Although 11 animals were seropositive for Anaplasma marginale by competitive enzyme-linked immunosorbent assay (cELISA), these were interpreted with caution because of the lack of concordance between cELISA and molecular detection assays. All animals were PCR negative for presence of Babesia spp. DNA, and a single nilgai was seropositive for Babesia bovis and Babesia bigemina by complement fixation. It remains unknown whether cattle Babesia spp. can establish an infection in nilgai.

Sperm Depletion in Singly Mated Females of the Mexican Fruit Fly (Diptera: Tephritidae)1

Abstract  Female Mexican fruit flies, Anastrepha ludens (Loew), have the capacity to produce more than 1,000 eggs over their lifetime, but fertility of the eggs will depend on the females capacity to store semen or to replenish semen through remating or both. The two parameters are interrelated in that sexual receptivity depends to a large degree on insemination status. In this controlled study, we measured sperm depletion in singly mated females with continuous access to oviposition substrates by using a squash technique. The spermathecae were sequentially emptied of sperm over the 3 weeks following copulation. Under laboratory conditions, sperm was always found in the ventral receptacle up to 4 weeks following copulation, but was empty in almost all females by the fifth week. These results mirrored previous measurements of egg fertility in singly mated females, which declines at 26–40 d postcopulation.

The Authorityand Types for the Hackberry Gall Psyllid Genus Pachypsylla (Riley) (Hemiptera: Psyllidae)

ABSTRACT: The nomenclatural problems with the hackberry gall psyllid species names are rectified. The genus Pachypsylla Riley, 1883, type species, Psylla venusta Osten-Sacken, includes 14 nominal species: Pachypsylla venusta (Osten-Sacken, 1861); P. celtidismamma Riley, 1875; P. celtidisgemma Riley, 1885; P. celtidisasterisca Riley, 1890; P. celtidiscucurbita Riley, 1890; P. celtidisglobula Riley, 1890; P. celtidispubescens Riley, 1890; P. celtidisumbilicus Riley, 1890; P. celtidisvesiculus Riley, 1890; P. celtidisinteneris Mally, 1894; P. dubia Patch, 1912; P. pallida Patch, 1912; P. tropicala Caldwell, 1944; and P. cohabitons Yang & Riemann, 2001.