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Jamaican Field Crickets - Gryllus assimilis.
Also known commonly as “Silent” Crickets.

Pros and Cons:-
+This species of cricket are more resistant to higher humidity than Black crickets.
+They can therefore be maintained at much higher densities than Black crickets.
+Their bodies when dead in the colony tend to dry, causing less of a rise in humidity and ammonia.
-They do need to be kept at slightly warmer than room temperature.
-They are less productive then Black crickets if your demand is for hatchlings or smaller sizes.
-They do not gut load as well as Black crickets which take on a larger amount of gut content on average.

Temperature and Humidity:-
Jamaican field crickets do best kept at a constant of between 25-30C.
Higher temps speed up the life cycle and can be used to time hatchings more efficiently. Eggs of this species kept at 30C hatch within 11days, fairly consistently and the nymphs are most successful maintained at 30C for the first 3 weeks before a drop to 25C slows the development to longer lived rate.
At these temperatures this species will reach adulthood in 6-7 weeks.

Humidity with crickets is a serious concern, while these insects need humidity in order to shed properly, even with raised temperatures, the average humidity in any building in the UK is sufficient. No additional humidity needs to be provided.
In fact, any rise in base level humidity can cause mass die offs in cricket colonies, it is very important not to allow moisture to gather in the containers or to allow moist foods in contact with the floor (where they will rapidly raise local humidity and also cause moulds/fungus).
Containers for crickets must be well ventilated and dry. This will affect which foods you may choose to use.

Foods:-
While there are many options out there and many people seem to have success with other foods, this outlines the foods I have used successfully for 2 years with a medium scale breeding project.

Hatchling nymphs - 3 weeks old;
Fresh foods used are Orange “ends” (shallow slivers, the nymphs will drown easily otherwise), Potato and Carrot slices. The food should be offered to smaller crickets under layers of card, not on the floor or exposed on the top of the colony.
These foods while fresh will provide enough water for the crickets, if the fresh foods used are changed daily or every other day (which is necessary for higher density colonies anyway) there is no need to provide any additional water e.g: crystals, gel etc.

Dried foods are only limited by your ability to find something dry that contains 25% protein only. Dog biscuits are usually 25% and higher quality Primate “leaf eater” pellets too.
For this age range of nymphs the pellets can be blended down or crushed into a powder and scattered in small amounts in the container, you should add enough to feed them for only a day or two at a time, any more and you end up with a film of mould instead ;)

3wks nymphs - Adults;
Fresh foods can be slices of Orange, Potato and Carrot. Once the crickets are larger and more inclined to feed in the open, the food should be placed on the top of the colony, covered food encourages flies by the million…
Although some people offer greens also, the container will need the card replaced more often as this tends to cause the crickets to do rather wet poo everywhere!
Other foods are tempting to use, but experimentation quickly reveals that many go “soggy” in the container ruining the card while the above 3 all dry leaving no mess. Certainly avoid any soft fruits whatsoever (Papaya, tomato etc are just a disaster…)

Dried foods can simply be whole pellets of the same type as for the smaller nymphs, again 25% protein is important. Again, although many use bran, rolled oats or similar as the dry base food, it is fairly void and is very problematic to keep clean and dry, also encouraging mould, fungus and flour mites.

General maintenance:-
Depending upon how many crickets you’re keeping, the size of your containers and how fast you are using them, you may want to “changeover” your containers on a weekly basis. If you begin to suffer die offs, the remainder need to be separated from the dirty container ASAP.
At this point you are removing any dead bodies, any missed food that has fallen to the bottom of the container and keeping an eye out for nasties like “buffalo worm” Dermestid beetle larvae.

Ideally you need a second identical container to transfer the crickets to, before you begin the task the second container must be furnished with card (even a brief exposure to high humidity in an empty plastic tub is a death sentence for crickets as you’ll see in the pics later!).
Simply shake all of the crickets off the card or tubes you are using, once you have a tub full of crickets, dead crickets, old food, half eaten pellets and frass (cricket poo and bits and bobs), you can tip the container gently to allow all of the active crickets to run off into the new tub. You can hand filter the stragglers as the live crickets will grip your hands or a latex glove while buffalo worms and dead crix fall through ;)

Buffalo Worm:-
Dermestid beetle larvae are commonly called buffalo worms, fuzzies or “caterpillars”.
They are potentially harmful to your colony and are not a “clean up crew” both the larvae and adult beetles can decimate entire containers of smaller cricket nymphs, they will prey on crickets during shedding or any weakened crickets. They also enjoy eating their way through your nesting boxes…

Breeding:-
Female Jamaican crickets are easily distinguished from medium size (or 5th instar). Females have a long ovipositor almost the length of their body sticking out of their rear, even sub adult females have a partially developed ovipositor visible.
Females of this species lay around ~400 eggs.

It’s literally as simple as get a container, throw a load of adult crickets in, they will mate and the females will swell obviously with eggs and begin searching for suitable laying sites. If you find females trying to lay in or under the food fresh foods, you know immediately there is something wrong with the nesting areas provided.

A suitable nesting tub should be around 3” deep, filled with 2.5” of *Organic pesticide free* compost, this needs to be slightly compacted (if it is “fluffy” the females won’t like it!) and well moistened, you should be able to feel the coolness of the humidity in the tub with the back of your hand. It should remain moistened (by pouring a small amount of water on every few days or so) throughout laying and for the first 2 weeks of the hatching process.

You will have much greater hatchling success if you move the nesting box out to a separate container during your weekly changeover and add a fresh box in with the adults. Also, 1/2cm wire mesh cut to cover the surface of your nest boxes will prevent spent females and males climbing in and eating the eggs.
Nest boxes can be allowed to dry out and then discarded from the hatching containers after 3 weeks.


Most people will be keeping their crickets on this kind of scale, but the principles still apply;


On a much larger scale, this is on day one of hatching;


7 days into hatching;


Weeks 5-6 mediums to sub adults;


Adults tub showing nesting boxes;



All Images and Text Copyright © Charlotte Goble 2009
 
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