22 de mayo de 2020

Rearing limacodids from eggs in plastic containers or on leaves

Prologue

This link shows a female Thosea laying a couple of eggs on plastic.

https://www.inaturalist.org/observations/45673144

Although in an unnatural setting, it shows how these moths tend to lay on smooth surfaces. The advantage to them laying on plastic rather than on a leaf in our attempts to raise caterpillars are multiple. For one, a leaf tends to dry or mold during the often 7 day gestation period until hatching. Also, through the plastic with the add of a hand lens you can watch the embryos as they develop. Not only is this fascinating to observe, but it is practical as well, as it gives you a heads up on when the egg will hatch.

Rearing limacodids from eggs obtained from females captured at lights has the advantage of being able to identify the species from an adult, since larvae often die. You'll note all these 'UFOs' in Inaturalist and other websites. Having the moth first really helps!

Recognizing females: Other than Perola in the Neotropics and Taeda in Africa, I don't know of any examples of females with bi-pectinate antenna for the length or base of the antenna, common in males, particularly those with nettle caterpillars. However, there are many limacodids that have filiform (threadlike antennae), so another thing to look for in determining the sex is the abdomen. Many males raise the abdomen above the body when at rest. Females tend to have rounder and heavier abdomens, as the are gravid. Also, their flight at an illuminated sheet tends to be less active. Like many moths the females are less abundant at lights, though species with clear winged males can be the opposite, given that clear winged males probably fly either during the day or soon after sunset or before sunrise.

The major difficulties in rearing from eggs are that females are more difficult to find at lights (I prefer mercury vapor), occasionally you get unmated females or those that will not oviposit, and having to guess at suitable food plant for species whose food has not been presently reported. Rearing limacodids without knowing the food plant is not as difficult as some other moth groups owing to the polyphagy of a number of species. In species that have not been reared, however, I advise that you try hostplants recorded for many limacodids. Leaves from Prunus or rose bushes, for example, are often good plants, or those that you have found limacodids on in your area.

When capturing a female, place it in plastic container and put it in a dark place. Limacodids will often lay eggs on the smoothest available surface, thus they often will lay them on the sides of a container. It is important to keep scales from female from getting on eggs because they can promote mold. One way that this can be prevented is by placing female in several different containers or by removing the scales between the eggs with a fine brush after the female has been moved. The plastic also has the advantage of being able to cut out groups of eggs to be placed in smaller containers. A container made of clear thin plastic has advantage of later being able to cut out groups of eggs and being able to observe the development of the embryos. It can often be estimated within a day when hatching will occur the embryo filling the space in the egg, the absence of yolk and the well developed stemmata and mandible. Watering the eggs is also important in preventing desiccation, though care should be taken to be sure the eggs air dry before recapping the container. I presume your area in Assam is very humid, but I still advise a little of this watering to insure that scales from the mother are removed from the eggs (you can carefully brush off these scales, but these eggs are very fragile, so great care under a stereo microscope is needed). Alternatively, the female can be placed in a larger cage with a potted plant or with leaves with petioles in a plant pick to keep the leaf and the eggs from desiccating.
After the eggs hatch, in genera with smooth gelatines in later instars tend to feed in first instars (Cheromettia, Belippa, Narosa, etc). It is particularly important to delicately place newly hatched larvae that are on the plastic onto food plants with tiny camel's hair brushes, since they have difficulty crawling from plastic to host. Spiny larvae (Parasa, Thosea, Scopelodes, Miresa, etc) do not feed in first instar and molt again after a day or two, so they do not need to be moved from plastic to plant immediately. Leaves and fecula (=frass, droppings) also need to be changed every few days to prevent mold.
Alternatively, if you know the food plant, you can bag the moth on a plant with a fine mesh net. This has the advantage of not having the host dry out or get moldy and not having to transfer the larvae to leaves when cleaning containers, especially in early instars.
In all cases, after the female is finished laying, be sure to save the specimen as a voucher. Pin and label with a cross label to those larvae being reared is of upmost importance, of course.

Rearing limacodid larvae found in nature, as opposed to from eggs layed in container, has the advantage of knowing the true host, which has a higher probability of successful rearing. While for many species this is not essential since many species as highly polyphagous, knowing hosts and finding knew ones adds to our scientific knowledge of host plants and assists in finding additional larvae in the future. The latter becomes more important because it is often the case that you are often rearing parasitoid flies or wasps, especially when you find a late instar larvae. Of course you also want to save the flies and wasps for identification by experts.

Whether rearing from eggs or larvae, if you are keeping the larvae in a small container with host plants, the following are suggestions for successful rearing. Early instars are best kept in hard sided containers rather than plastic bags. It is important to prevent condensation since the early instars can easily drown, however, if kept too dry they will desiccate with the food plant. If larvae wander off the host to the side of the container, they can be moved back with a camel's hair brush, but much care is needed.

It is important to photograph larvae, whether found in nature or obtained from the eggs of a female. In the former case it is quite common for larvae to be parasitized by a fly or wasp. A reference photograph will enable better identification at a later time, when the identity of the larva is discovered. Furthermore, larvae that appear to be familiar can turn up to be closely related species or genera that are not presently known.
When you are successful in obtaining a large number of larvae, it is important whenever possible it is important to preserve a specimen of each instar, especially for species that have not been previously reared. This can be done by placing larvae in water that has been boiled for two minutes and then transferring the specimen to 70% ETOH. If it is a late instar, the fluid should be changed over the next few days.
These larval specimens can be used to describe the life history and be useful in determining the relationship of the species or genera to others.
One last comment: in addition to saving various larval stages in ethanol (those that older, please boil in water for a minute before putting into the 70% ethanol), please save the cocoons and the skins associated with them. You can do this in dry vials. In all cases, be sure that the voucher numbers match with the adult female that laid the eggs. Many limacodids will eat their larval skins when they molt (often at least 8 times), but if they don't, save the skins in ethanol, too.
Also, if though I don't know of any of the nettle species that eat when they first come out of the egg, please make a note about this fasting behavior. Perhaps you'll find an exception to the rule.

Now I hope I haven't completely discouraged you! This is truly one of the most amazing groups of moths due to their amazing caterpillars. Detailed knowledge of various installs, particularly the 1st, 2nd, and last few is particularly important to understanding how there are such diverse forms within one group of Lepidoptera. Indeed, this is a group where ontogeny recapitulates phylogeny: you know the ontogeny, you know the evolution. Not always the case, but in this family I'm convinced from the evidence I've seen. cluster of them.

Ingresado el 22 de mayo de 2020 por marcepstein marcepstein | 8 comentarios | Deja un comentario

08 de mayo de 2020

Faux specimens

We make a small image of a photo from an iNaturalist observation and capture the data, including the link to it on iNaturalist. We cut them out in little rectangles and place them on a pin like a specimen, hence the name ‘faux specimen.’ Then they are placed along with actual specimens in my research collection. This way we can keep track of these finds that I either can’t identify to species or add info of the distribution or variation of named and unnamed species. If the faux specimen doesn’t match any others in the collection it is placed in its own unit tray located near what we think are its closest relatives.

Ingresado el 08 de mayo de 2020 por marcepstein marcepstein | 3 comentarios | Deja un comentario

01 de marzo de 2020

How to raise slug and nettle caterpillars, Limacodidae, and their relatives in the Zygaenoidea: Megalopygidae, Dalceridae, Aididae and Somabrachyidae.

Over the last three years I have been encouraging observers in iNaturalist to raise caterpillars of the Limacodidae in particular and to let me know what plant that they found the larva on. I'm a specialist in the Limacodidae in particular, but have also delved into research on the superfamily Zygaenoidea.

I'm hoping over time to develop a worldwide network to raise as many of the 2,000 species of Limacodidae, this rather charismatic moth group, as possible. Caterpillars, like their adults, present a number of challenges in being correctly identified by specialists. Like the adults, you have lookalikes that are indeed the same species, but also lookalikes that are different. In reverse, we also have very different looking caterpillars and very different looking adults that are indeed the same species. Sometimes, males look very different from females, as well.

I will be adding much more to this post in coming weeks, but for now, I do want you to use caution in raising caterpillars, particularly those covered in spines or hairs For example, in many Megalopygidae the spines lurk beneath the hairs.

Two basic ways to rear caterpillars are to place them in a container that is ventilated with tiny holes punch in the top or keeping them on their plant surrounded by fine mesh netting (best close to your home or where you trust your 'pillars won't be disturbed).

Handling: Don't try to grab spiny caterpillars directly. You can clip or pull the leaf off or cut off the end of a branch before placing them. You can also use a small brush to move a caterpillar directly to a container/leaf. This takes a bit of practice to have them grip on to the brush. For smaller caterpillars, a moist brush helps hold on to them, even from above.

Avoiding stings: Keep in mind, also, that it is the back of your hands and soft skin on your arms, legs and rest of body that are most vulnerable to stings, which can be quite painful.

Many of the nettle caterpillars also have tiny spines called caltrops at the base or tips of the subdorsal scoli (warts) on the sides and rear. These detach and can end up in your skin. Although these are not painful like the larger spines on the scoli, they are irritating to the skin. Often these caltrops do not form until the 3rd or 4th instar. The longer, often darker ones, on the rear segments form even later. I refer to these as deciduous spine patches. Both caltrops and the longer spines often are found in the outer layers of the the cocoon silk, so handling cocoons of the nettle caterpillars with rubber gloves is recommended.

Ingresado el 01 de marzo de 2020 por marcepstein marcepstein | 15 comentarios | Deja un comentario

Archivos